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Agrylic ground on the reverse of the canvas

Question asked 2023-05-18 08:29:31 ... Most recent comment 2023-05-23 15:17:39
Acrylic Oil Paint Flexible Supports

​This question relates to oil painting on a flexible support (canvas) on stretchers, and primed with an acrylic primer;

Has there been any testing, or studied historical examples, where a layer of acrylic ground was applied to the back of the canvas? (The canvas would be sandwiched by two layers of acrylic.)
The idea is that it would decrease susceptibility to changes in atmospheric moisture as well as stiffening the canvas.
What are your views on this idea?

Thanks in advance,
Ron Francis.

Providing the best Construction cost estimation for House

Question asked 2023-05-23 03:47:01 ... Most recent comment 2023-05-23 03:41:00
Grounds / Priming

If you’re looking for a dependable platform that helps you save thousands of dollars and provides top-notch construction estimating services, then stop looking and say hello to Accurate Estimates! We promise to be your one-stop solution for material takeoffs and estimating services for commercial, residential, and industrial projects. With our extensive experience and expertise in providing accurate material estimates, we ensure you achieve success when you’re bidding.


Our teams of expert construction estimators are highly trained and proficient in utilizing the latest versions of various latest software, so you stay a step ahead of your competition. At Accurate Estimates, we strive to deliver exceptional service and quality workmanship to you. Contact us today to learn how our professional estimating services can benefit your construction project and potentially save you thousands of dollars.

Pierced Traditional Gesso, Hardboard, Egg Tempera and SID

Question asked 2023-04-29 10:33:13 ... Most recent comment 2023-05-22 16:12:37
Rigid Supports Grounds / Priming Animal Glue Egg Tempera

​Hello Mitra !

I have developed a way of working that occassionally pierces my traditional gesso down to the hardboard panel below. They are small, slightly larger than pinhole "pokes" caused by drafting tools. I had begun this without thinking of consequences, but it occurs to me now that I could be inviting future problems such as surface induced discoloration or other problems I am not aware of.

Limited research I've pulled up on other areas of this forum suggest that SID is not likely a problem for egg tempera on traditional gesso, but these comments were regarding consistently gesso'd surfaces, and not punctured ones like mine.

I haven't painted these panels yet but in the past I have accidentally sanded a mall part of my gesso surface down to the hardboard and did not perceive discoloration on the finished piece.

Am I at risk of drawing up junk from the panel below into my egg tempera surface?

Could I fill the little holes with something prior to paintings?

Am I worrying too much?

thank you!

Small Business Lending in the Post-Pandemic World: What You Need to Know

Question asked 2023-05-20 19:18:41 ... Most recent comment 2023-05-20 19:18:00

The COVID-19 pandemic has caused widespread economic disruption, particularly for small businesses. Many small business owners have struggled to access the capital they need to stay afloat, making small business lending more critical than ever. This article will explore the world of small business lending in the post-pandemic landscape, including the types of loans available, factors to consider when choosing a lender, and alternative funding options.

Small business lending pre-pandemic

Before the pandemic, small business lending was primarily done through traditional sources such as banks and credit unions. These lenders offered a variety of loan types, including secured and unsecured loans, lines of credit, and equipment financing. However, these lending options often had strict requirements, including high credit scores and collateral.

Alternative lending options, including online and peer-to-peer lending platforms, emerged to fill this gap. These options were often more accessible to small business owners with less-than-perfect credit, but they also came with higher interest rates and fees.

The post-pandemic small business lending landscape

The pandemic has significantly impacted the lending market for small businesses. Lenders have become more cautious, resulting in fewer lending options and higher requirements for borrowers. However, government initiatives like the Paycheck Protection Program (PPP) have relieved small businesses with low-interest loans to cover payroll and other essential expenses.

Despite these efforts, small businesses still need help accessing capital. Many lenders have adapted their offerings to meet small businesses' needs, including longer repayment terms and more flexible collateral requirements.

Types of small business loans

Small business loans come in many forms, each with benefits and drawbacks. Some common types of small business loans include:

Secured loans

Secured loans require collateral, such as real estate or equipment, to secure the loan. This collateral is used as a guarantee for the lender, reducing the risk of default for the lender and resulting in lower interest rates for the borrower. However, if the borrower defaults on the loan, the lender can seize the collateral to recoup their losses.

Unsecured loans

Unsecured loans do not require collateral but often have higher interest rates and stricter requirements. Because there is no collateral to secure the loan, the lender takes on more risk, resulting in higher interest rates and more stringent requirements for borrowers.

Lines of credit

A line of credit is a flexible form of financing that allows a borrower to draw from a pre-approved credit limit as needed. Lines of credit can be secured or unsecured and often have lower interest rates than credit cards.

Equipment Financing

Equipment financing is a specialized form of lending used to purchase or lease equipment for a business. These loans are often secured by the equipment and offer longer repayment terms than other small business loans.

Factors to consider when choosing a small business loan

Choosing the right small business loan can be a daunting task, but there are several factors to consider when making your decision:

Interest rates

Interest rates can vary significantly between lenders and loan types. Be sure to compare rates from multiple lenders to find the best deal for your business.

Loan terms

Loan terms, including repayment schedules and loan amounts, can vary widely. Ensure you understand any loan terms before signing on the dotted line.

Repayment schedule

A repayment schedule outlines when and how much you'll need to repay each month. Make sure you can realistically meet these obligations before taking on a loan.

Collateral requirements

Secured loans require collateral, which can be seized if you default. Ensure you have the necessary collateral and understand the risks before taking on this type of loan.

How to apply for a small business loan

Applying for a small business loan can be a complex process, but there are several steps you can take to make the process smoother:

Prepare a business plan.

Most lenders require a detailed business plan outlining your company's goals and financial projections. Make sure your project is well-crafted and realistic.

Gather financial documentation

Lenders will require various financial documents, including tax returns, bank statements, and profit and loss statements. Make sure you have all of these documents organized and ready to go.

Choose a lender

Research lenders to find one that offers the best rates and terms for your business. Be sure to read reviews and check their reputation before applying.

Alternative funding options for small businesses

In addition to traditional loans, there are several alternative funding options for small businesses:


Crowdfunding involves raising funds from many individuals, often through online platforms. This can be a good option for businesses with compelling stories or products.

Angel investors

Angel investors provide capital to startups in exchange for a share of ownership. This option can be attractive for businesses with high growth potential.

Venture capital

Venture capital involves raising funds from investors to grow and scale your business. This option best suits businesses with high growth potential and a proven track record.

Risks and challenges of small business lending

Small business lending comes with its own set of risks and challenges, including:

Default rates

Small business loans have a higher risk of default than other loans, resulting in higher interest rates and stricter requirements.

Predatory lending practices

Predatory lenders often target small businesses with high-interest rates and hidden fees, so it's essential to research and choose a reputable lender.

Impact on personal credit

Many small business loans require a personal guarantee, which can impact your credit score if you default.


Small business lending is essential for the success of many small businesses, particularly in the post-pandemic world. With a variety of loan options available, it's necessary for business owners to carefully consider their needs and options before choosing a lender. By understanding the different types of loans available, factors to consider when choosing a loan, and the risks and challenges of small business lending, you can make an informed decision that will help your business thrive.


  1. What is the difference between a secured and unsecured loan?
  2. A secured loan requires collateral, while an unsecured loan does not. Secured loans often have lower interest rates, but unsecured loans are less risky for borrowers who don't have collateral to offer.
  3. How do I choose the right lender for my small business loan?
  4. Research lenders and compare rates and terms to find the best fit for your business. Read reviews and check the lender's reputation to ensure they are reputable and trustworthy.
  5. What is a personal guarantee?
  6. A personal guarantee promises to repay a loan using personal assets as collateral. Many small business loans require private security, which can impact your credit score if you default.
  7. What are some alternative funding options for small businesses?
  8. Crowdfunding, angel investors, and venture capital are all alternative funding options for small businesses. Each option has benefits and drawbacks, so carefully consider the best choice for your business.
  9. What are the risks of small business lending?
  10. Small business lending comes with risks such as higher default rates, predatory lending practices, and impact on personal credit. It's essential to do your research and choose a reputable lender to minimize these risks.​

Hire a professional hacker! (Telegram: Blackhat_plug)

Question asked 2023-05-18 23:59:33 ... Most recent comment 2023-05-18 23:58:00
Chalk Crayon Drying Oils Animal Glue Acrylic

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ratio pigment to oil, or is it: oil to pigment?

Question asked 2023-05-09 09:20:05 ... Most recent comment 2023-05-18 09:43:47
Paint Making Oil Paint

​Dear members,

When I am making paint with my students, I often use the Artist's Handbook by Ralph Mayer, fifth edition, for the ratios oil to pigment. Or is it pigment to oil?

When reading page 63 (right before the charts of pigments starts), I read: "The oil-absoprtion-rate figures give the ratio of pigment (by weight) to oil (by weigjht) needed to form a stiff paste."

But when we apply this, it often turnes out wrong, very wrong. Sometimes it seemes I misread, and it should be the ratio of oil to pigment.

Like with titanium white Mayer says: Ana 18-30 wt/ 100wt. So about 25 grams of pigment to 100 grams of oil. While in the Just Paint (by Golden) article about oil, weight and ratios, it says 20 grams of oil to 100 grams of pigment. So the other way around!

Who should I trust (other than my own results). Did Ralph Mayer make a mistake?

Thanks in advance

13 Ways Investing in Remedy Skin Tag Remover Can Make You a Millionaire!

Question asked 2023-05-17 03:23:38 ... Most recent comment 2023-05-17 03:22:00

​Features:Remedy Skin Tag Remover is a compelling liquid condition that can help people with discarding the huge number of moles, blemishes, and skin tags present on their faces while similarly discarding the vulnerabilities they could have about how their skin looks. To sort out the way this capabilities, clients need to have more data about its components and handle the science behind it.

best material to size wood panel?

Question asked 2023-05-17 00:35:15 ... Most recent comment 2023-05-17 00:26:00
Grounds / Priming Oil Paint Sizes and Adhesives Rigid Supports

​Dear MITRA community,

there are many conflict info regarding what to use or even if we need to size a wood panel for oil painting.

from on line resource, some saying can use GAC100 or gloss acrylic medium to size a wood panel. 

but from GOLDEN, they revised their suggestion by saying to avoid these gloss medium in any preparation layer if intend for oil painting, so instead they recommend apply acrylic gesso directly on wood panel without a need to size first. 

however, people argue if wood is not sized/sealed first, the water content from porous acrylic gessos would keep soaked into wood and causing issues. 

i also see other people using PVA size to seal the wood instead, however from the PVA size manufacture, it is only intend to use on fabraic canvas and paper, so it is also uncertain if it is good on wood or causing any permanence issues, as well as it introduced additional foreign material that complex the structure as well. 

so i want to ask that shall the best is to apply acrylic gesso directly on wood or we need to size it first, then what will be the best material to use? 


Understanding the Section 179 Deduction for Business Owners

Question asked 2023-05-16 17:40:11 ... Most recent comment 2023-05-16 17:39:00

As a business owner, you are always on the lookout for ways to save money and maximize profits. One way to do this is through tax deductions, and one deduction that may be beneficial to you is the Section 179 deduction. In this blog post, we will explore what the Section 179 deduction is, who is eligible for it, how it works, and what the benefits of using it are.

What is the Section 179 deduction?

The Section 179 deduction is a tax deduction that allows businesses to deduct the full purchase price of qualifying equipment and/or software purchased or financed during the tax year. This deduction was created as an incentive for businesses to invest in themselves by purchasing new equipment and technology.

Who is eligible for the Section 179 deduction?

Any business that purchases, finances, or leases qualifying equipment and/or software during the tax year is eligible for the Section 179 deduction. This deduction is available for both new and used equipment and software, as long as it is new to the business.

How does the Section 179 deduction work?

Businesses can choose to deduct up to $1,160,000 of the cost of qualifying equipment and/or software in the tax year in which it was purchased. The deduction is limited to the total amount of taxable income the business generates for the year, so businesses may not be able to use the full deduction in one year. However, they can carry over any unused deductions to future years.

What are the benefits of using the Section 179 deduction?

By taking advantage of the Section 179 deduction, businesses can reduce their taxable income and save money on taxes. Additionally, the deduction can help businesses invest in themselves by allowing them to purchase new equipment and software that can help them grow and be more efficient. 

What qualifies as qualifying equipment and/or software?

Qualifying equipment and/or software includes machinery, computers, software, office furniture, vehicles, and more. To qualify, the equipment or software must be used for business purposes more than 50% of the time. Additionally, the equipment must be purchased, financed, or leased and placed into service before the end of the tax year. Access Section 179 Deduction Calculator


In conclusion, the Section 179 deduction is a valuable tax deduction for businesses of all sizes and can help businesses save money on taxes while investing in themselves. By understanding what the Section 179 deduction is, who is eligible for it, how it works, and what qualifies as qualifying equipment and/or software, businesses can take advantage of this deduction and reap the benefits. So, consider consulting with your tax professional to explore further how the Section 179 deduction can work for you and your business.​

Question regarding oil lead ground and oil lead white paint

Question asked 2023-05-10 06:37:08 ... Most recent comment 2023-05-15 13:49:38
Grounds / Priming Art Conservation Topics Oil Paint

​Hi! While researching, I have come across some interesting comming from Angel Academy of Art's founder, Michael John Angel, about lead use in oil painting. I was interested in using a lead oil ground or lead alkyd ground on top of a surface prepared with acrilyc gesso as I have read lots of statements implying lead provides great strenght to the surface and further paint layers.

''This is great, but who would use dingy lead white these days? Over a short time, the lead combines with the sulfur in today's air and forms lead sulfide (and lead sulfide is black). I am a huge fan of Michael Klein's, but why not use titanium white (aka, the perfect white)? Titanium's only defect is that it's a slow drier, but mixed with an alkyd (such as Liquin), or bought in alkyd form, that defect goes away. It might be worth pointing out that there is a misapprehension about lead white: because it's so heavy, the assumption is that it is opaque. This is simply not true; it is fairly transparent. Lead white, like so many other pigments, is composed of round crystals, which bump together but leave a bunch of gaps. Titanium, on the other hand, has needle like crystals, which mesh together and form an opaque and permanent layer with no gaps. The Old People (guys & gals) used lead white simply because it was all they had. Today, we have much better paints than they did.''

Although both his comment and the fact lead white provides a strong film are not exclusive, I would like to know some conservator's opinion on this regard. Are the aforementioned drawbacks of lead (both ground and paint) sufficient to consider rulling it out, or its strength and other good properties make it still worth it? Specially when using it as a ground that will be fully covered. 

Thank you so much for your time, kind regards.

oil on top of acrylic pours

Question asked 2023-05-15 10:38:49 ... Most recent comment 2023-05-15 10:32:00
Oil Paint Acrylic

I have been seeing a lot of professional painters using acrylic cell pours as an underpainting and then painting in oil on top. Exemple: Sarah Slappey1
I don’t know if the acrylic cell pours were made using Dawn dish soap or Isopropyl Alcohol. In either case, would it be as archival as painting with oil on top of regular acrylics, or because of the soap or alcohol it would make it even less archival?

Some artists also say “oil painting only” in their info, example Rick Leong2, but me and other oil painters friends can’t see how you could do a bubble / cell effect in oil paint, if that is something that exists that you could point to! Thank you!


What Small-Business Owners Need to Know About SBA Loans

Question asked 2023-05-12 18:42:44 ... Most recent comment 2023-05-12 18:42:00

An SBA loan is a great way for investors to access capital for their business. However, it’s important to understand the ins and outs of an SBA loan before you apply. This blog will provide an overview of what investors should consider when getting an SBA loan. 

Eligibility Requirements 

Before you can even begin thinking about getting an SBA loan, you must make sure that your business meets the eligibility requirements set forth by the Small Business Administration. The requirements vary based on the type of loan but generally include things like being a for-profit business, being located in the U.S., having fewer than 500 employees, and more. It’s important to make sure that your business meets all of the eligibility requirements before applying for a loan. 

The Application Process 

Once you have determined that your business is eligible for an SBA loan, you can begin the application process. The application process generally involves gathering financial documents such as tax returns and profit/loss statements, filling out paperwork provided by the lender, submitting supporting documents such as contracts or leases, and waiting for approval from the lender. Generally speaking, it takes anywhere from two weeks to two months for an application to be processed so it’s important to plan ahead if you need access to capital quickly. 

Loan Amounts & Terms 

The amount of money that a lender is willing to lend varies based on factors such as credit history and collateral available but generally falls between $5,000 and $5 million. Additionally, lenders may offer different terms depending on factors such as credit score or type of collateral offered so it’s important to shop around and compare different offers before deciding which one is right for you. Generally speaking though, most loans have fixed interest rates with repayment terms up to 25 years. For small business owners, SBA Loans are a great source of financing for many investments, whether for working capital, buying an existing business or real estate. 

SBA has two loan programs - SBA 7a and SBA 504. SBA Loan calculators are available online that can help you calculate your ideal SBA loan to cover the costs of those investments. The SBA Loan Calculator helps you determine the best SBA loan options based on your own financial situation and eligibility criteria. This one-stop shop is especially useful for those looking to quickly compare different SBA loans side-by-side and make an informed choice. It's also important to get help from other finance professionals, as some SBA loan applications require additional documents or need more complex calculations than what can be found with a basic calculator.

In conclusion, getting an SBA loan can be a great way for investors to access capital for their business but it’s important to understand what goes into obtaining one before applying. Business owners should ensure that their business meets all of the eligibility requirements set forth by the Small Business Administration and prepare all necessary financial documents prior to submitting their application in order to increase their chances of approval. Additionally, they should shop around and compare offers in order to find one that works best with their needs and budget. With thorough research and preparation beforehand, investors can be confident when they decide on which SBA loan is right for them!​

What Small Business Owners Need to Know About SBA Loans

Question asked 2023-05-12 18:39:51 ... Most recent comment 2023-05-12 18:38:00

<p>An SBA loan is a great way for investors to access capital for their business. However, it&rsquo;s important to understand the ins and outs of an SBA loan before you apply. This blog will provide an overview of what investors should consider when getting an SBA loan.&nbsp;</p>

<p><strong>Eligibility Requirements&nbsp;</strong></p>

<p>Before you can even begin thinking about getting an SBA loan, you must make sure that your business meets the eligibility requirements set forth by the Small Business Administration. The requirements vary based on the type of loan but generally include things like being a for-profit business, being located in the U.S., having fewer than 500 employees, and more. It&rsquo;s important to make sure that your business meets all of the eligibility requirements before applying for a loan.&nbsp;</p>

<p><strong>The Application Process&nbsp;</strong></p>

<p>Once you have determined that your business is eligible for an SBA loan, you can begin the application process. The application process generally involves gathering financial documents such as tax returns and profit/loss statements, filling out paperwork provided by the lender, submitting supporting documents such as contracts or leases, and waiting for approval from the lender. Generally speaking, it takes anywhere from two weeks to two months for an application to be processed so it&rsquo;s important to plan ahead if you need access to capital quickly.&nbsp;</p>

<p><strong>Loan Amounts &amp; Terms</strong>&nbsp;</p>

<p>The amount of money that a lender is willing to lend varies based on factors such as credit history and collateral available but generally falls between $5,000 and $5 million. Additionally, lenders may offer different terms depending on factors such as credit score or type of collateral offered so it&rsquo;s important to shop around and compare different offers before deciding which one is right for you. Generally speaking though, most loans have fixed interest rates with repayment terms up to 25 years. For small business owners, SBA Loans are a great source of financing for many investments, whether for working capital, buying an existing business or real estate.&nbsp;</p>

<p>SBA has two loan programs - <a href=""><strong>SBA 7a and SBA 504.</strong></a> SBA Loan calculators are available online that can help you calculate your ideal SBA loan to cover the costs of those investments. The <a href=""><strong>SBA Loan Calculator</strong></a> helps you determine the best SBA loan options based on your own financial situation and eligibility criteria. This one-stop shop is especially useful for those looking to quickly compare different SBA loans side-by-side and make an informed choice. It's also important to get help from other finance professionals, as some SBA loan applications require additional documents or need more complex calculations than what can be found with a basic calculator.</p>

<p>In conclusion, getting an SBA loan can be a great way for investors to access capital for their business but it&rsquo;s important to understand what goes into obtaining one before applying. Business owners should ensure that their business meets all of the eligibility requirements set forth by the Small Business Administration and prepare all necessary financial documents prior to submitting their application in order to increase their chances of approval. Additionally, they should shop around and compare offers in order to find one that works best with their needs and budget. With thorough research and preparation beforehand, investors can be confident when they decide on which SBA loan is right for them!</p>​

using a polyester support

Question asked 2023-05-09 21:31:20 ... Most recent comment 2023-05-12 16:21:09
Flexible Supports

After centuries of use, I remain amazed that cotton and linen supports have yet to be replaced by some suitable synthetic such as, and specifically, polyester.  I stretched a piece of 12” x 12” polyester and then primed it with two coats of acrylic gesso. If I’m correct, I can paint directly on that support using acrylic, so that’s the first sort of question. However, I paint predominantly with oils. Because the poly will not be negatively affected by the linseed oil in my paints, might I assume that a sizing is not required prior to priming polyester supports with an alkyd ground?

The Ethics of Using Online Assignment Help Services

Question asked 2023-05-11 10:28:40 ... Most recent comment 2023-05-11 10:26:00

As the demand for <a href="">pay someone to take my teas</a> grows, so does the need for online assignment help services. While these services can provide a convenient and stress-free solution for students who struggle with their coursework, the ethics of using them remain a controversial topic.

On one hand, paying someone to take your TEAS exam or complete your assignments for you can be seen as dishonest and unfair to other students who are completing their work independently. It may also violate the academic integrity policies of your school.

However, others argue that[url=]pay someone to take my teas [/url] help services can be a valuable resource for students who are facing personal or academic challenges that make it difficult for them to complete their work on their own. These services can help level the playing field and ensure that all students have access to the support they need to succeed.

Thoughts on Odd Nerdrum & Co.'s "old master" canvas priming method?

Question asked 2023-05-07 01:11:28 ... Most recent comment 2023-05-09 05:56:37
Oil Paint Animal Glue Grounds / Priming


I found this video the other day, and was interested to try this method, if it can acquire your seal of approval.

This appears to be two layers of just linseed oil and "chalk" calcium carbonate, with a dollop of color-of-one's-choice for toning. Two layers of this, applied five days apart, and you are ready-to-go in ten days' time. Allegedly.


(18) How to prepare a canvas like the Old Masters | Demonstration by Jan-Ove Tuv - YouTube

00:12:08 - :00:12:16: "The canvas, which of course is pre-glued, by all means." 

Additional comments: Though some in this "school" use RSG, this particular canvas in the video "is a "pre-glued" Claessens 066GL." (So, PVA?).

"At least two [layers], but you can do three (as I mention towards the end: the ground will then suck [absorb] much more, but that can also be exploited to your advantage - depending on the technique you prefer)"


In this second video, this Nerdrum-school painter uses the same method of priming, but adds an "alkyd resin," and relays how this prevented his painting cracking while being rolled. 

(18) Learn to Paint like the Old Masters from Odd Nerdrum's Prominent Pupil Sebastian Salvo | Part I - YouTube

Discussion of his priming and preparation method from 00:05:30 until 00:11:00. I am also assuming this is pre-glued, though there is no verbal mention.




This first one, without the alkyd medium, interests me, but is it really enough to do:

layer 1) RSG or hide glue (or PVA, I imagine)

layer 2) linseed oil - calcium carbonate - dollop of paint. five days to dry

layer 3) linseed oil - calcium carbonate - dollop of paint.  five days to dry


Any thoughts? The non-toxic nature, and quick drying time (I do not have access, in my region, to some oil grounds I see advertised by painters on YouTube, that dry in two weeks or so).

Thank you


oil mediums

Question asked 2023-04-28 05:07:10 ... Most recent comment 2023-05-08 05:47:52
Paint Mediums Drying Oils

Dear Moderator,

​I was inquiring about the ratio of stand oil to solvent. The first way I paint is in a thin realistic manner. I was going to add a stand oil medium (25% oil 75%solvent plus cobalt drier 0.5%, calcium drier 1%, zirconium drier 1%) in the underpainting stage, and then with the final layer add a medium to the paint of 35% stand oil plus drier. Is this roughly correct for oil ratios? The second way I paint is a thick fluid impasto, painted in one layer. What ratio of oil to solvent would be appropriate (would it be 35% stand oil plus driers)?

regards Sam

Thoughts on Odd Nerdrum & Co.'s "old master" canvas priming method?

Question asked 2023-05-07 01:10:22 ... Most recent comment 2023-05-07 00:59:00


I found this video the other day, and was interested to try this method, if it can acquire your seal of approval.

This appears to be two layers of just linseed oil and "chalk" calcium carbonate, with a dollop of color-of-one's-choice for toning. Two layers of this, applied five days apart, and you are ready-to-go in ten days' time. Allegedly.


(18) How to prepare a canvas like the Old Masters | Demonstration by Jan-Ove Tuv - YouTube

00:12:08 - :00:12:16: "The canvas, which of course is pre-glued, by all means." 

Additional comments: Though some in this "school" use RSG, this particular canvas in the video "is a "pre-glued" Claessens 066GL." (So, PVA?).

"At least two [layers], but you can do three (as I mention towards the end: the ground will then suck [absorb] much more, but that can also be exploited to your advantage - depending on the technique you prefer)"


In this second video, this Nerdrum-school painter uses the same method of priming, but adds an "alkyd resin," and relays how this prevented his painting cracking while being rolled. 

(18) Learn to Paint like the Old Masters from Odd Nerdrum's Prominent Pupil Sebastian Salvo | Part I - YouTube

Discussion of his priming and preparation method from 00:05:30 until 00:11:00. I am also assuming this is pre-glued, though there is no verbal mention.




This first one, without the alkyd medium, interests me, but is it really enough to do:

layer 1) RSG or hide glue (or PVA, I imagine)

layer 2) linseed oil - calcium carbonate - dollop of paint. five days to dry

layer 3) linseed oil - calcium carbonate - dollop of paint.  five days to dry


Any thoughts? The non-toxic nature, and quick drying time (I do not have access, in my region, to some oil grounds I see advertised by painters on YouTube, that dry in two weeks or so).

Thank you


Imitation Mussini oil paint (that uses dammar) concerns

Question asked 2023-05-03 07:46:08 ... Most recent comment 2023-05-07 00:51:41
Oil Paint Paint Mediums Paint Making


About one month ago (quite accidently) I learned that a very affordable, locally-made artist grade (very high pigment load, minimal fillers) paint I'd been using for a few years uses dammar. This is before switching to, at the same price point, known and respected global brands' mid-range and student paints. The price of these local paints is great, but most importantly: a very lightfast pigment selection and the colors are ultra-luminous (it is no longer mysterious how this is happening), but now I am worried about long-term consequences.  I am only guesstimating: ~ 4-5% dammar per tube of 60ml.

I want my paintings to last 100+ years. 

What can I do to combat any soon-to-manifest issues in my existing pieces? What types of damages can I look forward to / should I be looking out for, in the years to come? 

The works are all unvarnished, for now.

Also: how can I safely use the remaining paint, or should I not?  

I was imagining I could use it in a top layer, as a glaze, ontop of non-dammar-based oil paints. Is this advisable at all if, say, it is mixed with some other medium? Maybe Pebeo's acrylic based medium (for oils)? Or perhaps liquin? AUXILIARIES 200 ML XL COLOURLESS PAINTING MEDIUM► Colorless XL Painting MediumProperties: Alkyd resin based,  Good resistance to yellowing,  Cleaning : Mineral spirits or turpentine

(I have no idea how foolish this last suggestion is, I am just brainstorming out loud.)

Thank you very much, so few people exist in real life and online to discuss these topics...​​

do we really need to seal the wood for oil painting?

Question asked 2023-05-06 00:01:10 ... Most recent comment 2023-05-07 00:37:55
Acrylic Art Conservation Topics Oil Paint Rigid Supports

​Dear Mitra community,

i want to ask do we really need to seal the wood for oil painting? i am using acrylic gesso ground and oil painting on top of engineered wood panel, called Masonite tempered hardboard. 

from one online source, i heard people saying wood had to be sealed before applying any acrylic grounds, because acrylic product had water, if wood is not sealed, the water content will wrap the wood immediately. but the source not specify which product is best to seal the wood that bonds acrylic ground well.

and i also see people suggest to use gloss acrylic medium to seal/"size" wood panel before apply acrylic gesso. however i think all acrylic is porous, so not sure how gloss medium can really seal the wood? even it could, its water content will wrap the wood first?

in addition, i see Golden is now advising not to use gloss medium any more if for oil painting, they suggest to apply acrylic gesso directly in several coats. then the question will be if apply acrylic gesso directly, will it seal the wood? or its water content will keep wrap the panel in each layer?

finally the thought is do we really need to seal the wood and what is the best product to seal the wood? can acrylic gesso seals the wood and act as ground as Golden suggest is a good practice?

thank you. 

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Question asked 2023-05-06 16:46:01 ... Most recent comment 2023-05-06 16:45:00

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Inquiry regarding archival support options

Question asked 2023-04-14 07:30:49 ... Most recent comment 2023-05-04 08:38:56
Art Conservation Topics Oil Paint Rigid Supports Industrial and Non-Traditional Products

​Hello, I have been researching for a while with regards of finding the best archival support possible for my artworks. 

I am happy painting on wood, but the detrimental effects RH and temperature swifts have on this material encourage me to look for a better option. I have also tried unsealed anodized panels, but i am unsure on long-term adhession of oil paints. ​I will try to keep it simple, as out there are many varied options. ​​

​​I am currently driven towards painting on ACM supports, but I am dubious on which subtype to choose. ​I am not too fond of plastic, having read it to not be expected to be as durable as metal, which leaves me with Honeycomb or Alucobond panels. 

​On the one hand, I am interested in trying Honeycomb panels, but being located in Europe, getting Artefex's ones is too expensive due to the shipping costs. I would like to test a sample before buying a bunch of them to save, but that seems unfeasible. ​

On the other hand, I found advice from Mr. Ross Merrill, former chief conservator of the National Gallery, where he recommended the use of an Alucobond panel glued to a Sunbrella poolyester fabric. I like this approach the best, as Alucobond seems to be the best option out of all the ACM types I have read about. 

I have already asked Sunbrella and, although they claim their current anti-moisture coating to not be as easily removable by hand as before, they were happy to offer me some fabric samples for me to check (still pending to be shipped from France). Meanwhile, I find myself incapable of getting an Alucobond panel smaller than 400x150 cms and coated with a polyester fabric upon which to glue the Sunbrella one, for better adhesion. 

​I would like to ask for advice on whether or not I am being too fussy, as ​Dibond is easily available, but again I am not a fan of cheap plastic cores. Am I right making that assumption? 

Maybe honeycomb panels from Artefex are the best way to go, and just testing the Sunbrella fabric to check if it's worthwhile or just sticking to ​​their lead oil panels in case not. At least for the time being, before getting any huge one directly from a manufacturer.   ​

Any advise highly welcomed and appreciated, thank you.

​Kind regards,

Jesus Boltzmann

Longevity of a work, if mixing Van Gogh oils and Rembrandt oils

Question asked 2023-05-01 08:59:35 ... Most recent comment 2023-05-03 15:51:19
Oil Paint


I possess a little of everything from Royal Talens' oils, and wonder:

Can I mix Royal Talens Van Gogh oils with Royal Talens Rembrandt oils into one another safely? 

If not, can I do large passages with a color from Van Gogh, isolated from details where I would use strictly Rembrandt oils? 

Do I immediately cut the longevity of the painting in half by using Van Gogh oils?

Thank you​

Is it safe to use dyed linen?

Question asked 2023-04-26 05:10:43 ... Most recent comment 2023-05-01 15:47:03
Oil Paint Flexible Supports


I found some large fragments of rather quality, thick, dyed (ochre-colored), Italian linen for a good price. I did not purchase it yet.

Is it safe to use dyed linen to create a larger stretched canvas?

Even if primed and gessoed adequately, what risks are there with the dye in the linen, in terms of long-term degradation?

It is far thicker than the raw linen available to me at present, so I thought I would ask.

Thank you very much!

Any known issues with using Iron Oxide pigments "for industrial use "in making oil paint?

Question asked 2023-04-30 02:18:38 ... Most recent comment 2023-05-01 15:45:03
Paint Making Oil Paint

​What is the chief ​difference in Iron Oxide pigments for industrial purposes, versus Iron Oxide pigments sold with the stated function of the production of artist's oil paint? 

Iron Oxide Pigments | Yipin USA

Thank you very much, MITRA.​

[HELP] best practice of preparing tempered hardboard for oil painting

Question asked 2023-04-28 13:31:10 ... Most recent comment 2023-04-28 13:16:00
Art Conservation Topics Grounds / Priming Sizes and Adhesives Rigid Supports

​Dear MITRA conservators,

appreciate your advice on the best practice of how to preparing an engineered wood support, like tempered hardboard, for oil painting. 

First, do we need to apply SIZE first? some peopel strongly direct wood must be size and sealed before apply acrylic gesso ground. the reason is if apply acrylic gesso directly on wood, its water content will wrap the panel, while if sized with a layer, then the water from gesso layers will not distort the panel. 

however, i had a doubt that the acrylic product used as size still had water content and all acrylic is porous, then how would it prevent wrapping since itself contains water and how it "seal" since it is porous? 

i am not quite sure how much different chemically the acrylic "size" medium different as acrylic gesso, as they should both be similar acrylic resin, then why cannot acrylic gesso be used as size, primer, ground all in one?

2nd, how to remove residue oil on tempered hardboard for optimum acrylic gesso adhesion? i assume the surface reflection is due to residue oil, and i wipe with IPA, but these shinny area still remains. and i brush a layer of water and find it beeds up. so it suggest i didnt sucessfully remove the oil residue. so any better way to do that and method to verify its removal?

3rd, the tempered hardboard surface is very gloss and smooth, so to welcome adhesion i see suggestion of sanding, so can we use scotch brite instead of sand paper? as i am afraid sanding too much. 

thank you. 


Question asked 2023-04-28 09:31:50 ... Most recent comment 2023-04-28 09:31:00

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[confused concept] do we really need sizing?

Question asked 2023-04-26 13:02:29 ... Most recent comment 2023-04-28 00:29:07
Grounds / Priming Oil Paint Rigid Supports Art Conservation Topics

​Hi here,

i am using acrylic gesso to prepare surface on raw fabriac canvas and tempered hardboard for oil painting.

so from people saying first step is to use a kind of gloss acrylic medium to "size" the substrate first, before applying acrylic gesso. 

my question is, what is the real difference between acrylic gloss "size" medium and acrylic gesso in terms of material? can we apply acrylic gesso directly on susbtrate as size, primer and gesso purpose all in one?

from what i reads, the gloss medium forms a more sealed surface that seals the substrate, so water or oil content from subsequence layer will not sink into the substrate anymore, but if it is a very sealed surface, how can acrylic gesso adheres well on top, we all know acrylic bond on porous surface only. 

in addition, i recently notice GOLDEN company revised saying no use of gloss medium under oil painting otherwise it would crack. so if we apply acrylic gesso, which is porous materila in nature, directly to substrate, what would happen? will that not adhere well to substrate? will that very porous so the oil will sink into substrate? 

OR, it is absolutly a best practice to apply gesso directly on substrate? if so, since acrylic gesso out of bottole is thick, do we want to dilute it very thin for fist layers, then slight dilute in latter layers? 

as i see Lascaux instruction, always dilute very big amount like 1:2 while other manufacture said cannot dilute more than 20%? so i am very confused. 


Question asked 2023-04-24 18:45:28 ... Most recent comment 2023-04-24 18:39:00
Sizes and Adhesives

​After reading over the MITRA resources on sizings, I saw Paraloid B72 was one recomended size. I paint in oil on wood or MDF panel. Are there any special considerations for applying primer/Gesso and/or oil paint on Paraloid b72? (oil based only, acrylic ok, etc?)


Question asked 2023-04-03 10:46:33 ... Most recent comment 2023-04-20 20:26:27
Paint Making

​Dear members,

Every time I am making Ultramarine paint with my students, it turnes out too long, or too short. There seems to be no middle ground. It either is too stringy or too gum like. 

When adding a little chalk, it suddenly turnes into gum when you press. And when leaving it, it just runs/ flows. Weird behaviour. And I don' t know how to solve this.

I already am using linseed oil with 2-3 % aluminum stearate, but it doesn' t seem to help. Also chalk doesn't do it, nor added beeswax. When adding more pigment it even becomes more runny.

I know "it is a property of the pigment" , but there has to be a way to make it yourself properly, right? What am I doing wrong, what might help?

​Thanks in advance.

Exhibition stand build Exhibiting in Europe

Question asked 2023-04-14 07:06:39 ... Most recent comment 2023-04-14 07:06:00

Participating in exhibitions can be a tedious and somewhat costly task, especially for startup companies and micro-businesses. Setting up a presentable and efficient exhibition stand may be hard for small companies while getting help from exhibition stands services agencies can be really a challenge.

Although it is not an easy task to join an event and manage an innovative exhibition stand, doing so can in fact produce outstanding results and propel a product or service to good results. Well designed exhibition booth design concepts together with a carefully planned business presentation strategy boosts four key vital business areas simultaneously, making a trade show slot a clever and worthwhile investment.

Set clear, measurable goals

Link objectives to precise measurements

Determine priorities and realistic targets

Outline a consistent way of measuring methodology.

Analyze results and work out recommendations

Branding and advertising

A lot of exhibitors attend trade shows and exhibit events. Thus, these are the perfect places for companies to increase the public awareness of their company. Regardless how small the exhibit area is, a great exhibition stand can help a company generate direct exposure and establish a trustworthy image.

Sales and marketing.

Exhibitions are great techniques for generating leads, flyer distribution, and product drive. Some exhibition participants also utilize their exhibition stands to submit new campaigns, attract potential clients, and even sell products or services.

Exhibition Stand Design Trends to Keep in Mind

There are factors that you must take into consideration first before you finalize your designs for your innovative exhibition stands. You need to seriously think about the various elements that you want to have in your stand. These components have to be interesting and appealing to your audience. Other than the visuals and well organized and harmonic environment to put in your stand, there are a few basics that you have to plan for too.

Relating to exhibition stand builder company stands, different styles have grown to be preferred in recent years when it comes to designs. Along with these are trends in lighting and building materials.

Aside from small businesses, big companies and multinational corporations usually participate in trade shows and exhibit events. Companies can meet key clients, business partners, and the must-knows in their industry. Trade exhibitions can also serve good recruiting centers where companies can spot potential employees.

Every interactive design can increase dwell time because it gives visitors the incentive to stay on your display. What happens? Everyone remembering your business. Interactive features such as an amusement park theme, complete that includes a ball pit and exhibits which can be explored, or even walked around and engage the guests' senses and make your company stand out.

Features that are interactive can be developed to be Instagrammable and your exhibit doesn't have to be static and will be shared across social media platforms and be able to engage with a wider viewers!

If you make your goals clear to the exhibit stand design company they'll know how to accomplish it. They'll also be able to offer suggestions or suggestions on the most effective method to achieve this.​

peeling varnish

Question asked 2023-04-11 04:51:20 ... Most recent comment 2023-04-12 08:56:57

​To Whom it May Concern,

I am having a varnish crisis and am hoping someone can direct me as to my best recourse.

After spending a significant time informing myself about picture varnishes via Natural Pigments, I decided the best course of action in varnishing a series of four oil portraits was to apply a coat of Paraloid B72 (to prevent sinking), and then a follow up gloss picture varnish.

Technical details:

6 month old oil based portraits

application of Kremer brand Paraloid B72 (15%) with UV protection 1 coat

1 week drying time

Application of "Sennelier gloss picture varnish" (1 coat)

after two weeks of drying time, when I removed the paintings from the stretchers to be rolled and shipped I noticed the varnish lifting in any areas that were mechanically bent, revealing that the varnish had not properly bonded to the surface. I am at a complete loss as to what went wrong. The paintings were created with very little oil and appear to be cured fortunately as the varnish is lifting without removing any of the paint film.

At this point, I am wondering what I should do to remove the old varnish without damaging the paint film underneath, and hoping someone can shed some light on what the problem may be, as the paintings will still need to be varnished after hopefully removing the failure. They are heavy Umber paintings, and I would like to apply an isolating varnish before the final picture varnish to prevent sinking.

I am located in Europe and any products that you may recommend would be most helpful. I was able to locate certain resins here via natural pigments EU site, but am unsure what solvents to use do dissolve them because they do not sell them on their EU website and I will have to procure them separately. When contacting them for help in understanding what solvent to use they have not responded.

I would be immensely grateful for any advice you may offer.

Kindest regards,



The admission Checklist of documents in Bachelors and Masters in Canada

Question asked 2023-04-06 19:29:23 ... Most recent comment 2023-04-06 19:28:00

The process of applying for admission to a Bachelor's or Master's program in Canada can be both exhilarating and overwhelming. One of the most crucial steps in the application process is to ensure that you have all the required documents in order. The absence or incompleteness of any documents can cause delays in processing your application or even lead to rejection. To assist you in navigating this process with ease, this article will present an admission checklist of the necessary documents for Bachelor's and Master's programs in Canada.

Academic Transcripts: Academic transcripts are an essential document for any admission application. They provide information about your academic performance, such as the courses you took, grades earned, and cumulative grade point average (CGPA). You must provide official transcripts from all educational institutions you have attended, including high school, college, or university.

Language Proficiency Test Results: If English or French is not your first language, you may need to take a language proficiency test, such as IELTS, TOEFL, or CELPIP. These tests assess your ability to communicate in English or French, and you must submit official test results directly from the testing agency.

Personal Statement: A personal statement or statement of purpose is a written essay that explains your motivation for pursuing a specific program, your career aspirations, and how the program aligns with your goals. This is a vital document that enables you to showcase your personality, experiences, and skills beyond your academic transcripts.

Letters of Recommendation: Letters of recommendation are written statements from individuals who know you well and can vouch for your academic ability, character, and potential. You should choose individuals who can speak to your academic performance, extracurricular activities, or work experience. Most programs require at least two or three letters of recommendation.

Resume/CV: A resume or curriculum vitae (CV) is a document that highlights your academic and professional achievements. Your resume or CV should include information about your educational background, work experience, volunteer experience, awards, and any other relevant information that showcases your skills and accomplishments.

Additional Documentation: Some programs may require additional documentation, such as writing samples, portfolios, or test scores (e.g., GRE, GMAT). Review the program's admission requirements carefully to ensure that you have provided all the necessary documentation.

It's worth noting that admission requirements may differ depending on the program and institution. It's vital to research the specific admission requirements for each program you are interested in and double-check the application deadlines. Submitting all the required documents on time will ensure that your application is considered for admission.

In conclusion, applying for admission to a Bachelor's or Master's program in Canada can be a complex process that necessitates careful planning and attention to detail. The admission checklist of documents outlined in this article can help you ensure that you have all the necessary documents ready for your application. Remember to research the specific admission requirements for each program, double-check the application deadlines, and seek guidance from your academic advisor or admissions officer if you have any questions or concerns. Best of luck!

Check the entire canada course here :

thought about best painting practice-fat over lean

Question asked 2023-03-04 16:21:29 ... Most recent comment 2023-04-05 00:06:12
Oil Paint Paint Mediums

​Dear Mitra community,

this week some friend send a link on Youtube talkes about best painting pracetice, host by Natrual Pigment.  My understanding the point is paininting straight from tube (paste) thinnly in each layer and no need to worry about fat over lean rule. I truely appreciate their will to help artist iron out this confusing fat over lean concept for best painting practice, however i still see gaps it not covered and hope to discuss with the Mitra community. 

1, it is not that practicle to paint all layer straight from tube, especially initial layer, like toning surface, blocking in, which requires fluidty, with butter like paste it would take forever to tone a surface. so it had to be solvent diluted for these layers. And it is correct adding solvent increased PVC, thus weaker film, however it creates a more porous film that readily accepting following layer and the oil from top will consolidate it as well, so even like water color consistency i not really see any issue as long as oils add back from following layer. 

and since ealier layer always lacks of oil (higher PVC), it becomes critical to add oils to the paint on following layer proportionally, so this makes paint straight from tube without medium not practically possible as well. 

2, besides discussed above, it also lacks consideration of fat vs slow dry color, even you paint all layer straight from tube thinnly but you paint a fast dry color over a slower one, i think it is probmatic as well. the best practice is to paint slower one on top of fast one always. 

3, especially there are many outlier color that is both fat (low PVC) but dries fast, so if you ignore this rule, you may likely to overlay a fast dry phathlo blue on top of a slower dry color say pyrole red.  Or you may paint a very fast drying and low oil content paint like Venetian red on top layer as fresh tone. 

in conclusion, my point is PVC view is a basic concept of how pigment absorbs oil, however by its alone it cannot cover fat over lean concept well, as it both about oil content as well as drying speed, especially when we considered many outlier pigments. 

i do agree due to market driven, most paint manufacture designed more for enthusestic hobbiest in mind who does care fat over lean with lean over fat so what mindset, but for serious artist, i do urge manufacture help artist to understand oil content, drying speed concept to avoid any confusion. 

i hope it may help open discussion about something like:

what you do if you need a fast dry & average to high oil content oil color over top of average to slow dry oil & lower oil concent paint? 

Get Your W2 Online: A Guide to Finding Your W2 and Understanding When W2s Come Out

Question asked 2023-04-03 20:38:15 ... Most recent comment 2023-04-03 20:37:00

Get Your W2 Online: A Guide to Finding Your W2 and Understanding When W2s Come Out

As the tax season approaches, individuals start preparing themselves to file their tax returns. One of the critical documents required for this purpose is W2. W2 is a form that employers issue to their employees, which summarizes their earnings, taxes withheld, and other deductions throughout the year. In this article, we will guide you on how to get a copy of your W2 online, including when do W2s come out and how to find your W2 online.

When do W2s come out?

Employers are required to send out W2s to their employees by January 31st of the following year. This means that you should receive your W2 by the end of January or early February, depending on how fast the mail delivery is. However, some employers provide online access to W2s, which makes the process much faster and more convenient.

If you do not receive your W2 by the end of February, you should contact your employer and request a copy. It is important to note that employers are required by law to keep copies of W2s for at least four years, so they should be able to provide you with a copy.

How to find my W2 online?

Many organizations are now wondering that their employees have the option of how to find my w2 online. This is a more convenient option since it eliminates the need to wait for a paper copy to arrive in the mail. Here are the steps to follow to get a copy of your W2 online:

Step 1: Check with your employer

The first step is to check with your employer to see if they offer online access to W2s. If they do, they will provide you with instructions on how to access your W2 online. You will likely need to create an account on their website and provide some personal information to verify your identity.

Step 2: Use a third-party service

If your employer does not offer online access to W2s, you can use a third-party service to get a copy of your W2. There are many websites and apps that offer this service, and some of them are free. However, be careful when using third-party services, as some may charge high fees or even be fraudulent. Always do your research and read reviews before using a third-party service.

Step 3: Request a copy from the IRS

If you cannot get a copy of your W2 from your employer or a third-party service, you can request a copy from the IRS. This should be a last resort since it can take several weeks to receive a copy from the IRS. To request a copy of your W2 from the IRS, you will need to fill out Form 4506-T, Request for Transcript of Tax Return. This form can be found on the IRS website.

In conclusion, getting a copy of your W2 online is a convenient and fast option. If your employer offers online access to W2s, be sure to take advantage of it. If not, you can use a third-party service or request a copy from the IRS. Remember to always be careful when using third-party services and do your research to avoid fraudulent websites.​

best practice if apply faster over slower dry oil color?

Question asked 2023-03-20 00:01:03 ... Most recent comment 2023-04-03 09:48:21
Oil Paint Pigments

​Dear Mitra community,

in practice we usually may in need apply a faster dry color over slower dry one, for instance, something like PR101 and PY42, which are very fast drying color maybe used on top of more slower drying one, like titanium white or some synthetic colors. 

And doing this will violate fat over lean rule if used as is, but will there any best practice we can apply in this order while still be free of archival problem?

maybe adding oil to faster dry one to slow it down?

preventing oil skinning

Question asked 2023-03-31 05:03:49 ... Most recent comment 2023-04-01 14:00:15

​Hello Mitra, I want to storage alkyd or oil mixed with solvent but it always generates a dried skin on the surface. Are there any products to prevent that? Thank you in advance.

Multiple nightmare problems in oil painting on traditional chalk ground panel. Non-crosslinked, sinking, tacky paint.

Question asked 2022-07-09 09:38:15 ... Most recent comment 2023-04-01 13:57:24
Chalk Grounds / Priming Oil Paint Solvents and Thinners Sizes and Adhesives Rigid Supports Varnishes Drying Oils Paint Additives Paint Mediums Scientific Analysis

Hi all,

I am having a huge problem in the painting I have been working on over the 18 months. I have been unable to find a cause and solution to the issue.

The paint doesn't appear to be crosslinking. I work in many layers, but if I run the back of my nail across some parts of the painting, I can remove all layers of dried paint back to the underpainting. 

I have had this problem before in other paintings, but never this bad. I removed as much of the unstable paint as possible at one point, removing around three months' labour. But if I test the recent layers, it appears that the problem is still occuring. 

  1. Panel was gesso'd with a rabbit skin glue to water ratio of 1:12. Whiting was added in a 1:1 ratio. Titanium white pigment no more than 10%.
  2. Once fully dried, the panel was sealed with a 1:3 damar varnish to turps layer. Sidenote, I have heard rabbit skin glue in 1:15 dilution is better?
  3. A thin coat of ultramarine and burnt umber was used to tone the panel. Potentially thinned with a small amount of turps (I can't remember).
  4. The first coat of paint was applied without any medium.
  5. Subsequent layers have had larger quantities of liquin and trace amounts of linseed oil (from cleaning brushes) added.
Initially I thought that it's because I'm using too much liquin. I do need to thin my layers out as much as possible, to the point where they are extremely translucent, but when the paint is scratched, it scratches down to the ultramarine/burnt umber tone. 
You'd think that the lack of crosslinking was due to overdiluting paint with alkyd resin, it would remove paint down to step 4. It doesn't. It goes all the way down to step 3.

I have used massive amounts of liquin in the past (up to 90%) and not had this problem.

The other issue is that the areas of ivory black are not tending to dry. They will remain just slightly tacky, indefinitely. It dries where I've used larger amounts of liquin, but without that, there's always a slight sticky feeling to it. The painting is monochromatic with large amounts of ivory black throughout. I have also used titanium white.

Lastly, the oil is sinking a lot. I believe that I may have overdiluted my damar varnish layer to seal the gesso. I haven't painted for a few years. I believe I did a 1:4 ratio by mistake. This issue is easily resolved with retouching varnish, but I haven't been able to use any yet due to fear that I'll remove all of the non-crosslined layers. Especially the pure black parts that are slightly tacky. 

It's making painting a nightmare as a result because I can't accurately judge the values. My blacks are appearing greyish. I need to use a retouch varnish to view it accurately, then I can finish the painting. I'm so close. I have thought about whether using a spray retouch varnish would be best, as it's less likely to disturb any dodgy areas. What's strange is that I have oiled out an area of ivory black with a very small amount of linseed oil. The linseed oil has remained tacky.

I would be so grateful for any help with this matter.

Essentially I need to stabilise the paint layers, get some retouch varnish down and finish the painting with some final adjustments. 

​Many thanks,


Varnish acrylic on linen

Question asked 2023-03-14 10:57:15 ... Most recent comment 2023-04-01 13:20:03

​I paint acrylic on linen, and am looking for a system of varnishing. I used the two step varnishing process of isolation coat (permanent acrylic coating), plus polymer removable varnish. Unfortunately the polymer varnish is no longer available in Australia, and am not sure when it will be. I am looking for an alternative. I have read that a  mineral based varnish can be used instead as a final coat. I have also read that several companies sell a varnish that is permanent and non removable. Is the 2 system (permanent plus removable) varnish better than the final permament non removable varnish. Logic tells me it is. Any guidance would be appreciated. Regards Sam

Preparing 6oz portrait linen

Question asked 2023-03-29 15:11:41 ... Most recent comment 2023-03-31 16:56:40
Flexible Supports Grounds / Priming

At my school we have 6oz fine/portrait linen and after priming it with one coat of RSG and one coat of titanium oil ground, I'm having doubts about painting on it. It seems too thin and fragile. Unfortunately no one at my school prepares their own linen so I'm hoping if you could please advise.

Is 5oz+2 coats sufficent weight for a 26"x26" painting? Should I add more oil primer coats, or should I put more coats of RSG next time? I was also thinking of bulking it up with acrylic ground but then read that RSG and acrylic is a bad idea...

Unfortunately I can't glue it onto anything as I have to roll all my work for flying it home..

Fiberboard and animal glue

Question asked 2023-03-14 17:48:15 ... Most recent comment 2023-03-27 07:47:25
Art Conservation Topics Egg Tempera Grounds / Priming Rigid Supports Sizes and Adhesives

​Hello MITRA society again,

In Rigid Supports under "Hardboards,Fiberboards,etc" is suggested that rabit skin glue (RSG) can be applied as size to this supports, althought followed with mounted canvas and then gesso.

My question is. 

If RSG can't be apllied over synthetic binders (acryl dispersion, alkyd, acryl resin) how can it work over fiberboard like MDF when we know it is wood fibers glued together with synthetic binder like urea formaldehyde? How can wood fibers then be impregnated with RSG size if they are soaked or encapsulated by this synthetic resin?

Mark David Gottsegen  in The Painter's Handbook: Revised and Expanded edition has table 3.1 on page 68 where he lists compatibility of adhesives/sizes to different supports, but fiberboard is missing from the table. Hardboard is applicable while chipboard is not with hide glue.

Damir Pusic. 

Particle Size

Question asked 2022-11-20 13:13:20 ... Most recent comment 2023-03-12 16:49:47

​Colored pigments seem to have a farily consistent particle size; for example, titanium white is listed as .5 microns, viridian generally listed as 2.5 microns, etc.  Filler or extender pigments (white or transparent solids) seem to come in a very wide range of particle sizes depending on use (from industrial to artist grade).  My questions are...

1.  Do synthesized colored pigments generally - or always - have a consistent, predictable particle size?

2.  How much can the particle size of artist grade, natural earth pigments vary?  Or are there standard, predictable sizes used within the paint industry?   

3.  Are filler/extender pigments mostly dervied from natural minerals? (The only synthesized filler/extender I can think of is glass powder...)  ​

4. Are artist grade filler/extender pigments ground/sieved to specfic sizes (are there industry standards)?  Or can they range all over the place?  For example, if I buy a "fine grade" chalk from two companies, can I expect them the same particle size?  If not, how much might "fine grade" particle sizes vary? 


GAC 400 for use in a multi-layed collage?

Question asked 2023-03-06 16:36:11 ... Most recent comment 2023-03-09 13:02:44
Acrylic Rigid Supports Sizes and Adhesives

​Hi All,

I'm involved in a project which consists of rendering/sculpting a rather complex (realistic) image onto a large piece of carpenter's grade 1/4" birch plywood. My ultimate goal is to create a low relief which - after a few coats of acrylic gesso - can be stained (in oil). 

So I've braced the plywood and also applied a light coat of acrylic size (to both sides). On the front I am proceeding to glue in collage/textural elements using GAC 400 (according to my design). I chose GAC 400 since that appears to be the recommended medium for creating and gluing collage elements - and also I use cotton, as that appears to be the recommended fabric type. Anyway, I coat the section to be glued (with the GAC 400), wet the  fabric first, squeeze out the water, then soak it liberally in the GAC 400. I press it into place, blot out excess liquid and leave it to dry 24 hours. After 24 hours, the fabric appears to be adhering quite well to its substrate and is also quite hard, allowing me to trim off superfluous edges. I should note that these are larger, thicker, coarsely textured foreground elements. So far, so good.

Now, as I begin to think about creating the background elements, I expect to be using thinner, finer fabric (due to its capacity to render lower relief). No problem, I have plenty of fabric with different thicknesses to choose from. However, from a working-method-point-of-view, I also know it will be much easier if - when it comes to the details - I can glue in a second piece of fabric over a previously glued one.

Thus I have finally arrived at my question: Will GAC 400 adhere to a dried fabric-embedded version of itself? Or should I use a different glue? If so, what? Would something as standard as Gorilla Glue be appropriate? My question arises from experience since I've learned the hard way that adhesion over the course of time is one of the greatest risks of experimenting with untested materials. Thus I've learned to do my due diligence (even as I push the envelope). As ever, I appreciate any and all informed responses from the experts assembled here.


Ellen Trezevant​​

Gum Arabic as gouache medium or glaze

Question asked 2023-02-20 10:50:06 ... Most recent comment 2023-03-05 10:11:43

​I paint in gouache, mostly tubed, but also the Lascaux bottled "tempera" gouache. I am painting on linen on cradled birch panels with linen applied with either dilute PVA glue, or rabbit skin glue (RSG) depending on the stiffness of the linen. The linen  is sized with RSG and then 4-10 layers of true gesso is applied as a ground. I want the linen for the texture.

I've started using gum arabic (GA) as an extender/glaze and wonder about long term cracking of the "glaze. Some of the layers are almost all GA (or 50% GA to water) as I am going for very dilute washes similar to Chinese ink paintings, and then more pigment as the subject matter comes to the forground. There is quite a bit of erasure in my process, using sponges and water, much reworking and layerring. The ground generally is preserved although to be honest I sometimes get down to the linen, or close to it. The look of "process" is important.

Q1: I suppose I assume that the interlinking of layers is preserved as all the layers are water-soluable. For example a very dilute initial glaze of 50/50 GA to water on true gesso binds well, and then subsequent layers with perhaps 100% GA glaze medium with greater amount of gouache/pigment, then perhaps pure gouache on that, possibly knocked back with a very water-wet soft brush. So you see there's a lot of back and forth. (I've noticed that the GA glaze is slower to "reactivate" that a pure gouche area and I use this to layer glazes to create certain effects.) My long winded Q basically is: Does my assumption that the universal water soluability of the various layers is sufficient to create a bond between those layers, despite different amounts of GA proportionally, application of water to erase, or pure gouache (no GA at all)?

Q2: Gum Arabic is expensive. A little Windsor Newton 2.5 oz bottle is about $12. A Schminke 200ml bottle is a bit cheaper per unit, but not much. I've seen a thread on using photo emulsion GA on another site but I cannot find anything on the use of Food Grade GA. You can get a gallon for the $50. It's similar in viscosity, and color. I've noticed that the Schminke contains "biocidal products", which leads one to conclude that there is an issue with GA "going off". It smells sweet, and "food-y". I havent tried it yet but as I am starting much larger paintings I need to find a source of cheaper GA, unless you tell me my method above will lead to everything falling onto the floor in a few years. Hopefully not.

If necessary can I add a biocidal product in small amounts to preserve the food grade GA? What would that be? a few dropd of bleach?? Sounds iffy...


Buy Undetectable Counterfeit Banknotes WhatsApp##:+346432O7724

Question asked 2023-03-04 18:17:02 ... Most recent comment 2023-03-04 18:16:00

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Fat Over Lean Solvent Free?

Question asked 2020-10-24 17:28:45 ... Most recent comment 2023-03-04 12:46:56
Oil Paint

​If I paint solvent-free with oil paint straight out of the tube for my first layer, and let that dry to the touch for my second layer, and so on for subsequent layers, do I have to make each subsequent layer fatter by adding a little oil to my paint nuts, assuming I use no solvent ever? Or since there is no solvent do I not have to make each layer fatter? Thank you.

Fat over lean in article on Natural pigments

Question asked 2021-04-21 09:16:19 ... Most recent comment 2023-03-04 12:42:31
Drying Oils Oil Paint Pigments

There is an article at by George O'Hanlon called „Painting for Posterity with Modern Oil Paints", about some aspects of oil painting. I'm posting a question about it here, because „Forum" section at hasn't been functioning for some time (or it seems that way - not possible to start a new topic) and also because George sometimes posts also here. I'd like to know his opinion – but of course everyone is welcomed to share their knowledge and experience.

Quoting from the article:

Fat-Over-Lean Rule

You are probably familiar with the fat-over-lean rule. What the fat-over-lean rule implies is flexible over less flexible paint layers. When you apply a more flexible layer on top of another, the final paint film will be more resilient and more resistant to cracking. Increasing flexibility is accomplished by adding more medium or oil, or lowering the pigment volume concentration of the paint with each succeeding paint layer.


However, this is typically difficult to achieve in practice. Most artists don't understand what constitutes fat or what is lean. It is impractical to measure the ratio of pigment and binder while painting. What I will tell you next may sound like heresy but you do not need the follow this rule if you use paint at its CPVC, which is applying paint straight from the tube, and paint thinly. On the other hand, working in thick paint layers and/or with lots of medium or oil added to paint requires one to observe the fat-over-lean rule.


I visit mitra forums from time to time and there already has been discussion about fat over lean, and so far, the conclusion was, that in fact every paint is formulated to be lean out of tube (i.e. made with just neccesary amount of oil, at CPVC or so).

The statement of my interest is : „(…) you do not need the follow this rule if you use paint at its CPVC, which is applying paint straight from the tube, and paint thinly." It is not clear, George was reffering to Rublev colors or any oil paint in general. And that makes me wonder; whether he meant paints based on various pigments in same oil, or in various oils as well.


You see, there are manufacturers like Williamsburg, Gamblin, Michael Harding and of course Natural pigments, who use linseed oil as a default binder for their entire line of oil paints and they also offer some pigments ground also in other oils like walnut or safflower. If one wants to use only linseed oil based paints, it is possible with these brands. But on the other hand there are many manufacturers who use different oils or oil blends for different types of pigments. One example I can mention is Blockx; they use linseed oil for iron oxides, natural earths, blacks and few other pigments (e.g. PY53, PY154, PY184) or blends (e.g. Paynes Gray, Indigo) and poppy oil for everything else, i.e. blues (organic and inorganic pigments), cadmiums, cobalts, organic reds, oranges and of course whites.


Now, let's say one wants to use Blockx oil paints to create grisaille underpainting using chromatic black (e.g. burnt umber and ultramarine) and flake (lead) white and then lay a glaze over it with transparent mars yellow and the painting will be done according to what George wrote, i.e. applying paint straight from the tube, and paint thinly.

Ultramarine and Flake white are in poppy oil, burnt umber is in linseed oil. Seems to me, that burnt umber is stronger than ultramarine, so more ultramarine will be necessary. Then, as grisaille needs to be bit lighter than a final painting would be in grayscale, relatively large proportion of white will be necessary; of course it can vary depending on particular part of painting, but my point is – this will result in paint layer consisting mostly from poppy oil as a binder. Let's say it'll be left to dry and cure for two weeks, and then the glaze based on Transparent mars yellow will follow; in case of this color, linseed oil i sused as a binder.

Therefore, it will be a paint layer with pure linseed oil as a binder over a paint layer with mostly poppy oil as a binder; is this alright? According to what I know and read so far, I'd say - not really... as oils like poppy and safflower should not be used in lower layers, because they form weaker layer. And yet, so far I haven't read any article or blog post about paint layers cracking in such situations.


I wonder, if it is really a problem, when one uses „weaker" oil like poppy underneath „stronger" oil like linseed. Whether it is only about oil, or also about pigment; lead white is known to make strong and flexible paint layer; is it possible that lead white in poppy oil will still dry into paint layer as strong as some other pigments in linseed oil?


What do you think about it?

Fat Over Lean & Adding Mediums; Same over same

Question asked 2021-05-24 13:25:20 ... Most recent comment 2023-03-04 12:35:22
Oil Paint

​I'm sure this has been addressed here ad nauseum and don't wish to create more work for anyone.  Can you please direct me to a resource that can educate me on the use of mediums and whether mediums that speed drying are considered fat?

I paint in layers without solvents and am currently using Gamblin's Solvent-Free Gel and Medium, both of which contain safflower oil and alkyd resin.  These mediums speed drying somewhat over using the paint neat.

I have read two conflicting viewpoints over whether the addition of mediums increases fatness.  One opinion is that the addition of any extra oil medium, regardless of whether it speeds drying time, increases fatness.  The opposing viewpoint is that any medium that speeds drying has also increased leanness.

I'm not sure how to think of this. 

Finally, does painting "same over same," as one might do when applying paint from the same brand without adding any mediums or other additives, violate the fat-over-lean rule?

Thank you!

Titanium white in 2023

Question asked 2023-02-27 13:16:12 ... Most recent comment 2023-03-03 14:06:18
ASTM Oil Paint Pigments Scientific Analysis Technical Art History

​Dear MITRA administrators,

Last year (2022) was writen a study: New insights into the deterioration of TiO2 based oil paints: the effects of illumination conditions and surface interactions​. [Thomas Schmitt] Full text available on

Conclusion states "Both anatase and rutile TiO2 based samples showed these characteristic markers of degradation under the visible and UV–vis light conditions used in these experiments. By measuring the change in intensity of characteristic degradation FT-IR peaks, we showed that anatase and rutile based paints facilitate similar rates of linseed oil degradation." 

Also, they explicitly wrote that coated TiO2 was not used in this study. [First passage under "Materials and methods".]

Based on all above, what do you suggest, to use it or maybe not in oil paint? 

Kind Regards,

Damir Pusic.

non-absorbent acrylic gesso is good for layered oil painting?

Question asked 2023-02-22 12:36:30 ... Most recent comment 2023-03-03 13:50:37
Oil Paint Grounds / Priming


i see some manufacture selling non-absorbent acrylic gesso for oil painting, the idea behind it is to overcome sink in with regular absorbent acrylic gesso. it maybe good for direct painting style, however i have few questions:

1, the adhesion between oil and acrylic is mechanical interlocking mechanism, if acrylic sucks oil into them, it means the surface area for adhesion is increase like 3D compared with if acrylic not absorb oil that adhesion is only at surface like 2D. so does this mean the adhesion of non-absorbent acrylic gesso is weaker?

2, with absorbent gesso, if painting in layer, because it sucks oil into ground, it systematically fat over lean as the lower layer gives oil so it becomes leaner once applied. however if it is not absorbent, then the layer will not gives its oil, so it may becomes more critical to judge oil content of each tube? which is very difficult. 

hope to see your comments! 

Seeking clarification about tooth

Question asked 2021-05-03 12:11:48 ... Most recent comment 2023-02-21 22:59:12
Grounds / Priming Oil Paint

Hi everyone, I was hoping to gain some clarification about tooth with regards to acrylic "gesso". I primed some canvases last week with Golden's acrylic gesso and am currently waiting a week for them to be fully dry. I have also been reading several commenters saying the surface is slick and not toothy enough for their liking with this brand (however most painter's I've asked swear by it, so I don't know if that's a common complaint). 

On Justpaint they had this line that intrigued me: “A toothy surface has adequate micro-texture to allow a subsequent coating to physically conform to that texture.” Is that suggesting that tooth is on a microscopic level and not necessarily a tactile observation? Could a gesso be slick to the touch, but actually microscopically mechanically bind? 

Or is it a little bit of both, like could a very textured-in-application but lower quality acrylic gesso make up somewhat for the lack of microscopic adhesion. 

I hope what I'm asking makes sense! 

Thank you!


thoughts on oil ground?

Question asked 2023-02-20 12:59:26 ... Most recent comment 2023-02-20 17:18:35
Oil Paint

​i have few questions regards oil ground, hope get advices:

1, how does fat over lean works out on oil ground? as we know, oil ground is not really lean, so when you apply highly diluted first layer, probably be leaner than oil ground, then will that break fat over lean rule, that causing issues?

2, does the oil paint adheres oil ground really good? i read a book saying oil paint may not adheres to oil ground, which i think makes sense especially when the oil ground cures in relative longer time that it forms a film that sealed, so not sure if oil paint layer would adhere there any good? by contrast, traditional gesso or acrylic gesso dries with good porosity and oil can sink into them for good interlocking adhesion. 

3, oil ground seperate from size? many people against acrylic gesso is saying oil may seperate from acrylic due to different flexibility, then will the same hold true for oil ground may seperate from acrylic/PVA size?

​4, does alkyd ground will also becomes brittle over time?

does tempered hardboard really a permenant archival substrate?

Question asked 2023-02-14 13:05:07 ... Most recent comment 2023-02-20 12:39:14
Rigid Supports

​Dear conservators,

i understand some drawbacks of hardboard like the corner is easily damaged but that can be resolved with care or frame around corner.

so my question is limited as regards tempered hardboard permenance with acrylic gesso primed for oil painting. As today even smaller amount oil used, but it still contains oil residue, so:

1, will the remaining oil residue (even not a continous film) on the surface or below the surface may migrating out that result seperation of gesso layer in longer time?

2, since drying oil will be brittle over time, does that the oil in the tempered board when brittled will negative affect the stability of the panel?

3, i heard lignin the natrual "glue" hold the filbers is pretty volitale that will leave the surface, so does this mean in a longer time, when enough lignin left, the panel will degrade down to fibers again?

4, to brace it, what kind of wood bar will be best and what kind of glue can be use, does regular wood glue is suitable? i am afraid if the panel may bow, the internal bond of wood particles will be less than the glue and the board get delaminated in long run. 

5, will it be a good idea to use varnish like Gamver to apply on the back side of panel to prevent moisture coming in and lignin lossing out?

Water mixable oil paint

Question asked 2023-02-18 08:30:26 ... Most recent comment 2023-02-20 12:19:22
Oil Paint

​Any insight into the archival properties of using water mixable oil paints either alone, or as underpainting?

Cradling panels directlly or after primer/ground?

Question asked 2023-02-15 13:10:52 ... Most recent comment 2023-02-16 12:32:52
Grounds / Priming Rigid Supports


For the first time I will try to brace my mdf panels. I read Rigid suports reference but still would like to gain further clarification.

When to glue wooden braces to reverse side of panel, after size but before gesso ground or after gesso ground but before primuersel?

Above I use term "primuersel" meaning thin oil ground applied on top of animal glue gesso as was desribed in book Rembrandt:Art in the making. I know about hygroscopic nature of animal glue.

Kind regards,

Damir Pusic.

Acrylic medium (gloss) as a wood sealer

Question asked 2023-02-03 06:39:29 ... Most recent comment 2023-02-13 04:07:53
Acrylic Sizes and Adhesives

​Would any decent quality (established brand) gloss acrylic medium seal a wood panel effectively?

There is a lot of advice online about sealing wooden panels with a gloss acrylic medium. The majority of the advice recommends using Golden gloss acrylic medium (or their GAC though Golden now say their medium is better for this job) though others refer to using any gloss acrylic medium. There are a number of good quality gloss acrylic mediums marketed for professional use though coming under the 'midrange' umbrella as well as excellent quality versions under the 'artist grade' umbrella. As far as I'm aware, Golden only produce 'artist grade' products. Considering the multiple coats and hidden nature of the sealing layers, it would be helpful to know what is suitable.



Differences between black oils

Question asked 2023-02-07 07:03:40 ... Most recent comment 2023-02-10 18:28:23
Drying Oils


Black oil by Natural pigments is made from linseed oil and litharge (lead oxide):

Recently I found out, that Holbein also offers Black oil, however according to description, this one is made from linseed oil and lead white (translated website):

Can you estimate, how the different form of lead (i.e. lead white instead of lead oxide) affects properties and behavior of black oil? 


Egg tempera in fountain pen

Question asked 2023-02-05 14:28:59 ... Most recent comment 2023-02-08 11:03:03
Pen Ink Egg Tempera Drawing Materials


Recently I started to use egg tempera (yolk+water and carbon black pigment) instead of pigmented indian ink to draw on paper.  I draw in closed room now in winter and would like to avoid hydrocarbons in indian ink.  The problem is that steel nib dip pen asks for frequent diping in egg tempera, so I think I will try to use fountain pen instead. On market there are ones with converter i.e, refilling option.

Is it possible to use fountain nib pen filled with egg tempera instead indian ink to draw on paper? 

Anyone have experience, Koo?

Kind regards,


Strange behaviour of Canada Balsam

Question asked 2023-02-07 07:52:57 ... Most recent comment 2023-02-07 09:14:05
Drying Oils Paint Mediums

​Seems that first attempt wasn't uploaded well, so I'll try again;

I tried to make medium from refined linseed oil, low viscosity bodied oil (45 poise) and canada balsam in proportions 60 % ​refined oil, 30 % bodied oil, 10 % canada balsam measured by volume. All three ingredients are clear and transparent, but as I mixed them, the mixture became cloudy. Here is the photo: 01.jpg I'm not quite sure, but I suppose that it shouldn't behave like that... I then let it sit and over following four weeks, sort of sediment formed in the bottle: 02.jpg

At this point, I'm not sure whether it is usable... I'm certain, that this was caused by canada balsam; when I tried Kremer larch balsam instead of canada balsam with the same proportions (i.e. 60 % refined oil, 30 % bodied oil, 10 % larch balsam), the mixture remained clear. In both cases I mixed the ingredients in bottle placed in hot water.

Do you have any idea, what happened an why canada balsam behaves like this? What should I do to prevent it?


Strange behaviour of Canada Balsam

Question asked 2023-02-07 07:41:55 ... Most recent comment 2023-02-07 07:16:00
Drying Oils Paint Mediums


I tried to make medium from refined linseed oil, low viscosity bodied oil and canada balsam in proportions 60 % ​refined oil, 30 % bodied oil, 10 % canada balsam measured by volume. All three ingredients are clear and transparent, but as I mixed them, the mixture became cloudy. Here is the photo:

After som three-four weeks


Question asked 2023-01-25 15:16:46 ... Most recent comment 2023-02-06 17:25:35
Paint Mediums


I have a couple questions about sealing cradled wood panels (I know alot of questions have already been answered in regards to sealing on this forum but I will try to not ask the same ones that have been answered) I work in larger sized cradled wood panels 36 x 36 inch (91 x 91cm)  and 48 x 48 inch (​122 x 122 cm) being my most frequent size. I use gac 100 to seal. The problem is working in this size is that I burn through the product very fast even with the 128 oz container. I plan to continue to use Gac 100 for the top of the panel to avoid SID as much as possbile but im wondering if there is another alterternative for the bottom to cut down on costs? since the goal for sealing underneath is to prevent the wood from rotting or warping do to humidy correct? so do you need to use GAC 100 for the bottom? there is alot of wood sealing products out there at big stores like home depot so im just curius is there other alternatives to gac 100? 

is Gac 100 really that special? they dont have the ingedients on the label and sometimes I wonder if this is to hide that there product really isint much diffrent then the lest costly products avaible at hardwar stores. I dont want to cheap out tho, and am commited to creating paintings that will last a long time espeshailly now that I am sellling pieces quite frequently - I want to make sure im not cutting corners but the costs for using golden on large scale works is intense. 

On that note im also wondering about isolation coat before varnashing, same problem - golden only has the isolation coat product avaible in a really small container, I've read that the soft gel could work as a isolation coat but not sure the correct process for diluting it. do you know of any larger quantity products availble for isolation coats before varnashing? 

I wanted to link some of the other selant products I have found online at harware stores for wood but it kept freezing when I copy pasted the link in.

Thanks in advance if you take the time to answer! 


Eco-friendly sizes

Question asked 2023-02-02 18:41:55 ... Most recent comment 2023-02-06 16:32:02
Sizes and Adhesives

​Is anyone aware of a size for oil painting that is not polymer based or rabbit-skin glue?

Concern about potential sunlight damage

Question asked 2023-01-20 01:04:53 ... Most recent comment 2023-02-06 12:32:42
Art Conservation Topics ASTM Drawing Materials Environment Matting, Framing, and Glazing Oil Paint Other Pastel Pigments Varnishes Watercolor

​Dear MITRA folks,

To make a long story short, a solo show space that I have been offered consists of a long wall on one side of a wide corridor/lobby where art is installed, and a long window opposite that allows light to hit the art wall all year long, with distracting shadow patterns of branches for good measure. When I voiced my concerns, I was told that there is a tint on the windows with "5% transmission" that cuts out 99% of the UV light rays. Would that be sufficient to keep any sunlight damage from happening over the course of a two-month period exhibit? Under normal conditions with brief periods of light coming in at only a certain time of day I would think so, but this window allows sunlight in all day long. 

I could help mitigate the risk by using varnish with UV protection where applicable or frame with UV protection glass where glass will be used, but I am wondering if oil, watercolor, or pastel should be out of the question for this show and that charcoal drawings might be a "safer" option? (My largest body of charcoal drawings were executed with non-traditional, homemade charcoal, if that makes a difference.) 

All of my materials are professional quality, and for the most part I use lightfast pigments -- all the oils are lightfast ASTM rating I -- though occassionally the watercolors made with natural pigments and crushed gemstones are graded ASTM II.  

Many thanks in advance for your guidance! 

Red Lacquer Paint

Question asked 2023-02-02 15:48:03 ... Most recent comment 2023-02-06 12:19:08
Art Conservation Topics

​what medium is used for Chinese red Lacquer paint

White substance on oil paintings

Question asked 2023-01-19 17:33:46 ... Most recent comment 2023-01-26 15:58:18
Oil Paint

​In cleaning my studio I found several oil paintings have developed a powdery white substance on the surface. The paintings range in age from two years to three months. I am unsure if it could be mold or an efflorescence due to the location on darker areas made with quinacridone, pthalo and umber. Can efflorescence develop very quickly?Powderypainting.jpeg

Medium is either linseed oil or galkyd and gamsol depending on the piece. The substance easily wipes off, though on the older paintings, it seems to have degraded the surface a bit (surface looks matte and dull). Some of the paintings were stored in a darker space on the floor, some hanging on the wall. None were wrapped. It has been more humid due to lots of rain lately. Other work nearby made with similar materials at similar times shows none of this substance. I have never seen this in more than ten years of painting in this space. I'm wondering if there's a way to narrow down the cause. 

How to remove bubbles from a gessoed linen

Question asked 2023-01-25 22:18:43 ... Most recent comment 2023-01-26 15:51:41
Mural Painting Flexible Supports

​Hello Everyone,

I recently posted this issue with the Painting Best Practices group and I recieved great information for how to prepare a large linen but not how to fix my specific issue.  I'm preparing a linen canvas thats 13ft x 16ft and my doing it over board. I only placed 2 coats of gesso and the second coat has created pretty big bubbles. Can someone offer recommendations as how to remove them? I dont know if this is a lost cause or if something can be done.

Thanks and take care 


Oil paint repellent

Question asked 2023-01-17 19:35:28 ... Most recent comment 2023-01-26 12:56:13
Oil Paint

​In the video "Jean Dubuffet: Brutal Beauty - Curator Tour" (, at 7m10s, the host says Dubuffet applies a mix of zinc oxide/varnish in order to repel oil paint. How does this technic works? Is there another similar way to create oil resistant regions on the canvas?

Tempera Grassa & Sun Thickened Linseed oil

Question asked 2023-01-16 11:31:45 ... Most recent comment 2023-01-19 16:23:10
Oil Paint Paint Mediums Drying Oils


I am new here! I am trying to become an illustrator so I’m trying to shop around for a quick drying (and archival) medium that doesn’t have harmful fumes. Aside from the regular solvent free alkyds, I’m considering two other mediums:

 1. Tempera Grassa

Could I use an egg oil emulsion as a quick drying medium? I’ve seen it talked about a few times here, but not much in detail. 

I’m particularly interested in because my family has 9 chickens in our backyard. 

I’m painting on acrylic gesso. Would it be fine to use as long as I:

  • Dont use it in the underpainting
  • Dont exceed 25% medium by volume
  • Paint on rigid support (ie Gessobord or other hardboard panel)

Or is it only suitable for glazing?

Could I use stand oil instead of regular linseed oil to make up for the brittleness of the egg?

Im also using safflower oil to clean my brushes, would egg residue contaminating the oil cause problems or spoil?

  1. Sun Thickened Linseed Oil

Most sun thickened oils I’ve seen cost a lot for just a little, so I’d want to make it on my own in the long term if I end up liking it.

I’m considering leaving cold pressed linseed oil in a glass jar covered by cotton fabric. The fabric would be held in place either the ring of a canning lid or a rubber band. 

Would it be ok if I only left it outside part of the time? I want to be able to keep an eye on it, I wouldn’t want squirrels getting into it. I’d try to leave when I had it in a sunny window indoors.

Thank you very much!


P.S. Is Tad Spurgeon’s website and book considered a reliable source? I actually stumbled onto Louis Valezquez while researching egg oil emulsions a couple months ago. I didn’t trust his lack of sources, but then heard Spurgeon had much better documentation (plus some friends who are chemists). 

I saw hes in your resources tabs, I’m just confused sometimes when his book conflicts with information on here. Acrylic grounds, alkyd mediums, and alkali refined linseed oil are ok’d on here, but he doesn’t trust them very much.

I’m sorry for all the questions! I’m new to oil painting and theres so much information to absorb.

Acrylic glazing over gold leaf

Question asked 2023-01-16 00:59:18 ... Most recent comment 2023-01-16 16:56:22
Gilding Acrylic Oil Paint

​There are several early Renaissance panels that use the translucent quality of oil glazing over gold leaf. Nevertheless, I always felt that paint over gold leaf creates really poor adhesion.

Is there a sealer you recommend to be applied before painting on over gold? I am interested in glazing with acrylics and with oils.

Thank you for your time and for this amazing forum!


Sanding sized canvas

Question asked 2023-01-07 14:27:44 ... Most recent comment 2023-01-12 05:16:32
Sizes and Adhesives

​Dear forum members,

I'm on the verge of adopting the practice of sanding sized canvases. I can thus remove unwanted knots and irregularities in the surface. First, I put two thin coats of PVA size on the stretched fabric, sand it smooth with fine sandpaper, and lastly, I apply another two thin layers of size. This way the PVA mitigates the damage/fraying, and I have a nice smooth surface to work on. By the way, I expected a Claessens 13 fine weave canvas to have virtually no knots, but I guess it's just the way fabrics are.

The simple question is: are there any concerns with this practice that I may not foresee? Should knots be "flattened" this way? An alternative would be sanding the canvas in between lead oil ground layers, but honestly I'm not keen on trying that one.

Kind regards,


using heat to speed drying

Question asked 2023-01-06 18:00:17 ... Most recent comment 2023-01-09 11:38:01
Oil Paint Drying Oils

​Are their any problems created in the paint film by drying a wet oil painting in a chamber heated up to 90-95 degrees F with 60 W incandescent bulbs?

Thank you,


movement in a drying oil film

Question asked 2023-01-06 19:13:20 ... Most recent comment 2023-01-08 06:45:07
Oil Paint Drying Oils

​As a paint film dries, I understand that it increases in mass rapidly as it takes up oxygen, reaches a zenith and then reduces in mass at a slower rate before "leveling out" at a very minimal incline,  indefinitely, when graphed on a chart.   Most of this change seems to take place within a few days, depending on the rate of drying.

As the paint layer gains and loses mass, does it also thicken, expand and/or shrink?

If so, it seems to me that the farther that the film progresses through these changes before another wet paint layer is added, the less movement the next layer has to deal with, especially getting past the more sudden gain and loss of mass in the first few days.  Longer and more rapid drying would seem to help in the "more flexible over less flexible" paradigm.   Correct? 

Thanks for your thoughts,


mixing lead white oil paint with titanium white oil paint to improve paint film

Question asked 2023-01-06 10:59:07 ... Most recent comment 2023-01-07 13:15:16
Oil Paint Rigid Supports

1.  ​What would be a good ratio of lead white oil paint to titanium white oil paint to get a stronger film than titanium white with more opacity than lead?  

2.  Do the benefits/charcteristics accrue according to the ratio of lead white or titanium or does a little bit of one or the other actually have a greater effect than one would expect?

3.  How important is a strong film formation if your support is rigid such as an​​ aluminum-composite panel (ie dibond, alumalite, etc) primed with an acrylic dispersion (Golden) and does not bend or move easily or expand with humidity?

4.  Does the importance of a strong paint film stem from its common use on hygroscopic supports such as stretched linen?   Is it as important if the support does not move? 

Thanks for your thoughts,


using heat to speed up drying

Question asked 2023-01-06 17:51:26 ... Most recent comment 2023-01-06 17:36:00

​I fashioned a 4' x 4' x 1' chamber with four light sockets, with 60 W incandescent bulbs, fastened to the top, into which I place oil studies or paintings for overnight drying.  The temperature will average about 90-95 degrees F (like a summer day in Florence during the Renaissance, ha, ha) depending on the distance to the bulbs.  It dries wet paintings more readily without the use of driers and if I repaint every four days or so, the paint film will be better "cured" than if the painting had been drying for the same time on a shelf.

Now that I've been using this method for about 20 years, is there likely any damage done to the paint layer that I have been creating, now that I've already done it?  So far, I cannot see any apparent problems.

Thank you,


Where can I find Lapis Lazuli pigments?

Question asked 2023-01-06 09:28:10 ... Most recent comment 2023-01-06 10:46:27
Oil Paint

​I have a deep love for the beautiful blues I see in old paintings. 

I've been eying micheal harding tubes (the only lapis lazuli pigment I can find here in the US), but I'm not sure of their quality. How good are they? I'd like the highest possible quality lapis available on markets if possible! 

Is there an online available alternative if the harding ones don't make the cut? 

Thank you! 

Removing Varnish problem

Question asked 2022-12-12 11:38:47 ... Most recent comment 2022-12-28 09:07:03
Acrylic Art Conservation Topics Solvents and Thinners Varnishes

Hi all,

​I have a somewhat perplexing problem. I have several acrylic paintings that once they had been dried for 1-2 weeks I applied an isolation coat (GOLDEN products), waited a few weeks and then applied Winsor & Newton Artists Acrylic Satin UV Varnish (bottle form). This is a removable acrylic that I like the Satin finish on more than other varnishes I have tried.

This worked well, but on one of these paintings the finish was uneven so I tried removing the varnish with the Winsor & Newton Artists Acrylic Varnish Remover in order to reapply afterwards but nothing happened. I tried adding more of the product and more vigorous movements with a soft cloth but it didn't remove the varnish or even seem to soften it. 

I made a test piece which I then varnished with the Satin Varnish and after a few days once it was dry I saturated the surface with varnish remover for 5 mins and then rubbed all over with a cotton cloth and again nothing happened, and I didn't see even the slightest change once the varnish remover was wiped off. I then also tried Gamsol (being odorless OMS) which did nothing as well.

At this point I emailed W&N and they said: "The varnish is based on an alkali soluble acrylic, the remover is alkaline in nature and should resolubilise the varnish so not quite sure why yours isn't working. I have heard of other artists adding a small amount of Rubbing Alcohol (ISO PROPANOL) to the remover normally 10 to 15 % 

As I say unless the alkaline material has evaporated it should remove the varnish"

On searching for the varnish on Google I found this link on CAMEO:

This suggests the varnish might be: "A brand name for a Polycyclohexanone based varnish that was previously sold as Winton Varnish. Artists' Gloss Varnish is composed of 46% Laropal K-80 dissolved in Mineral spirits with no additional components. The non-yellowing coating is typically used over oil, alkyd, or acrylic paints."

So following this being the possible composition I tried pure mineral spirits, which again did nothing!

The only thing which removed the varnish, but also damaged the acrylic on my test piece was Acetone.

Luckily my paintings have an isolation coat, but I am now at a loss for how to remove the varnish in the future.

I wondered if you had any ideas or suggestions?

Thank you,

Artist made mistake Prevention Zinc oil What to do

Question asked 2022-12-20 08:41:30 ... Most recent comment 2022-12-21 16:38:30
Oil Paint


I am a professional artist and I used zinc white in my last paintings. It had been years I haven't used it and I totally forgot about the zinc white problematic. They really should label tubes. It was Winton of Windsor and Newton. Feeling really scared and stupid. I used it in mixing with paint to have more transparent colors. In some parts it was more than 15%. It's linen stretched on aluminum bars with a Liquitex translucent gesso (worst case scenario I know). The paintings are finished and going for a show soon. I'm freaking out.

As an artist, I was wondering if there is anything I can do to help prevent the zinc white parts to crack? I know it's not good to oil out at the end, but could oiling out the precise area where zinc white was used could help in this particular case to add some flexibility? Perhaps with walnut oil so it yellows a little less? I would prefer yellowing over cracking and flaking. Or would varnishing help in any way to protect the surface from stress? Or what else should an artist do if they mistakenly used it? Thank you so much for your help!!!

Recovering art from smoke and soot damage

Question asked 2022-12-20 19:07:05 ... Most recent comment 2022-12-21 08:11:51
Acrylic Oil Paint Varnishes Health and Safety

​Greetings. I am one artist of a hundred artists who rent in a studio building in Houston that was bombed last night. The firemen were able to put out the fire and left the remaining studios on both floors with soot and smoke damage. None of us have been able to enter the building to assess the damage. One thing will be for certain, there will be damage. I am interested in organizing an email that can be sent out to all artists to hopefully help them with the first stages of getting our works back to some kind of order if they are retrievable. From what I understand, the smoke remnants is so dense that even hanging out for an hour in the building will leave one's clothing saturated with smell. 

I'm wondering if anyone could help with some tips on the following:

How can we

1. Remove soot from unvarnished acrylic and oil paintings

2. Remove soot from varnished acrylic and oil paintings

3. Remove smoke smell from unvarnished acrylic and oil paintings

4. Remove smoke smell from varnished acrylic and oil paintings

5. (This is for me) I have unvarnished acrylic paintings on wood panels that are for a solo show next September. The panels were coated with GAC100 or Gloss Medium prior to several layers of acrylic dispersion. From that point, I started painting with Golden Acrylic paints and Golden OPEN paints. 

I had planned on sealing the back of these with Polycrylic and sealing the front of the paintings with Golden Isolation Coat followed by removable varnish. Assuming I can clean the soot off of them prior to doing sealing the front and back of the paintings, do you think the layers of protection will help get rid of the smoke smell? Or, am I looking at trashing all of them?

I'm assuming all artworks on paper are destroyed. 

I realize these cleaning methods are best left to professionals, but seeing as how most of us barely make our rent on top of our full-time jobs, it would be great if we could get some information on methods that could be easily accessible by laymen and take our chances the best we can. 

Thank you for any information you can provide. This is a horrible way to start the holidays. 

Sanding RSG off panel to apply an acrylic size OK?

Question asked 2022-12-17 21:39:27 ... Most recent comment 2022-12-19 21:58:27
Oil Paint

​Dear MITRA 

I have some Masonite panels I previously sized with RSG, both sides, to which I glued canvas, but the paintings I did on these didn't work out, so I removed the canvas. I'd now like to paint on the panels but feel they will need an extra coat of size as some RSG came off with the removal of the canvas. Can I just sand the old RSG off and apply an acrylic size? Or should I just go for another RSG size to be on the safe side?

Stretching an oversized linen canvas

Question asked 2022-10-10 18:33:09 ... Most recent comment 2022-12-14 13:21:30
Flexible Supports Grounds / Priming Sizes and Adhesives


​I need to stretch an oversized linen canvas. Its 400cm x 500 cm or 13ft x 16ft.  I plan to use acrylic size and acrylic gesso, for the simple reason that i feel its going to be easier than using traditional materials.  After the painting is finished, rolled up and delivered, the plan is to fix it over flat wooden boards.    I mention all this because since its going to be placed over the flat wood,  since im going to use acrylic base materials for the preparation, and finally since its linen , do  i need to really "stretch" the linen? Can i just lay it out flat and size it and gesso it?   

If this is not the case, any suggestions for how to stretch something so large? Im only use to streching smaller size canvases or preparing wood.  

Tempura work from Reniasaance period?

Question asked 2022-12-11 05:16:43 ... Most recent comment 2022-12-13 14:05:29
Art Conservation Topics Technical Art History Oil Paint

​Hello, I was looking for advice and tips on how to verify if my work is an original piece from the Reniassance period, it looks like a tempura on wood Madonna and Child with gold. 


Question asked 2022-12-07 11:46:22 ... Most recent comment 2022-12-13 05:59:11
Health and Safety Pigments Studio Tools and Tips Handling and Transportation Environment


I thought that Threshold limit values (TLVs) or Permissible exposure values (PELs) are key parameters to monitor which substance i.e, pigment is more toxic.  Pigments/metals with lower TLVs are more toxic.  Am I right? Therefore lower TLVs call for stricter/lower mass to space (mg/m3) contamination. Time weighted average (TWA) defining time interval in which this TLV or PEL is averaged.

Lately, I started considering to use PW1 (lead carbonate) and find out that I cannot buy and use it for producing easel paintings. I live in EU. But cobalt and cadmium can easily be bought in the same market space.

Let us consider PELs for these three meatls, the NIOSH CDC pocket guide to chemical hazards lists:

Cobalt metal dust, Cobalt metal fume-OSHA PEL TWA 0.1mg/m3,

Lead metal, Plumbum-OSHA PEL TWA 0.050 mg/m3,

Cadmium metal-OSHA PEL TWA 0.005 mg/m3.

From this data it looks like cadmium is more dangerous than other two. I know that there can be difference in PELs regarding size of particulates (inhalable, repirable), but this is all I found. Why is then lead so dangerous that it needs special regulations?

Please can anyone clarify this very important topic? 

Damir P.

Using water soluble pastels (Neocolor II) under acrylic

Question asked 2022-12-06 13:56:55 ... Most recent comment 2022-12-07 14:28:51
Acrylic Pastel Crayon

I got into the habit of using Neocolor II pastel/crayons as the underpaintings for my acrylic on canvas; it only recently occurred to me that these contain some wax and may not be wise for the integrity of the acrylic. Granted I am using them activated so they have basically become paint, but I'm not sure if this makes a difference. Please advise.

Mural painting on panels

Question asked 2022-11-22 15:55:05 ... Most recent comment 2022-11-30 11:05:58
Mural Painting Rigid Supports

​I am undertaking a fairly large mural project in oils that will have to be done on panels that must abut and therefore have to be fastened to each other on site during installation. I would consider affixing canvas to the panels or working directly on the panel surfaces, if possible. I would appreciate any thoughts/experience you might have on best panels, how to join panels, etc. Dibond? Cradled wood? Gatorboard? 

One of my previous projects was done on panels of fiberglass over aluminum honeycomb. They were light, rigid and strong, but the surface was slightly dimpled—I would want to avoid that in this case. Many Thanks

Under drawing in conte crayon

Question asked 2022-11-23 15:54:55 ... Most recent comment 2022-11-30 11:03:22
Oil Paint Drawing Materials

​Can you tell me if it is structurally sound to use a conte crayon for a drawing under oil paint? Not worried about smears, only compatibility of materials. 

Actual Metals vs. Mineral Pigments?

Question asked 2022-11-20 11:56:56 ... Most recent comment 2022-11-30 10:50:46
Drawing Materials Pigments Grounds / Priming

​I've heard people say that titanium white and zinc oxide pigments work so well in metalpoint grounds because they are themselves metals.  To be clear: Titanium and Zinc are metals (which can, incidentally, be used to draw with in metalpoint).  However titanium white and zinc oxide are inorganic, mineral-based pigments, but not actual metallic compounds - correct?   I believe they work well in metalpoint grounds because of their relative hardness (6.5 and 4.5 respectively on the Mohs Scale), yes? 

Ultra absorbent ground.

Question asked 2022-11-14 13:18:56 ... Most recent comment 2022-11-15 02:38:28
Grounds / Priming

​Recently watched a video on You Tube. The artists Said he added something to his ground that made it more absorbent. Twenty minutes into the video oil paint was already touch dry. My question. Would this trap un oxidized oil between the ground and the canvas?

Bismuth white reactivity

Question asked 2022-11-02 07:43:25 ... Most recent comment 2022-11-14 19:25:52
Pigments Oil Paint


Do you know if there's any research on bismuth white reactivity with drying oil?

I gain information that bismuth white is on the list of reactive pigments. I wonder if it has positive effect similar to lead white, or negative like zinc oxide. If it's positive the leek of toxicity makes it a candidate to use as filler i.e, ageing agent to oil paint.

Kind regards,

Damir P.

Fine Art Shipping

Question asked 2022-11-04 08:20:56 ... Most recent comment 2022-11-14 14:27:27
Handling and Transportation

​I'm not sure this is an appropriate question for MITRA, so if it's not,​ Brian, feel free to shut me down. For shipping a painting, I usually just use Fedex and keep my fingers crossed.  I have a client wanting full coverage - beyone Fedex's liability - for a shipment.  Any suggestions for good, fine art shipping and/or fine art insurance for one painting, while in transit?

Best Way to Underpaint When Oil Painting Solvent Free?

Question asked 2022-10-08 20:05:27 ... Most recent comment 2022-10-10 19:04:22
Oil Paint

​I want to paint solvent-free with walnut oil paint straight from the tube, but I want to tone my canvas and then do an initial block in with a thinly applied fast-drying paint. I was going to use acrylics for this, but Golden recommends adding oil to paint from the tube if you underpaint with acrylic colors (as opposed to acrylic gesso). I would rather not add oil to the paint for my first layer. What is recommended for a fast drying imprimatura and first block in layer: watercolor? gouache? Water mixable oils thinned with water? casein? Thank you.

Satin Vanish query

Question asked 2022-10-07 11:10:20 ... Most recent comment 2022-10-07 11:04:00
Acrylic Art Conservation Topics Scientific Analysis Technical Art History Varnishes

Hi all,

I'm having some difficulties with applying satin varnish (W&N Professional Satin Varnish) or Gamvar Varnish with a brush and getting a completely streak free finish when using smooth panels for acrylic paintings. I've found the best results is with W&N Professional satin varnish and applying two thin coats at 90 degree angles to each other. But it's still not perfect.

I've tried the spray versions but there is a subtle dotty kind of pattern from the propelant/solvent which I am not keen on.

Am I correct in that apart from the impressionists most of the paintings you see and work on for your work are using a gloss finish for the varnish? It seems much easier to apply a gloss varnish and get good results, but then you have issues with lighting and glare when haning paintings in the home.

Any ideas? Is it just a lot of practice needed, or is there a fundamental limitiation with matting agents used in varnishes and getting a totally even finish?


Issues with strongly thinned paint layers for underpainting?

Question asked 2022-10-04 17:52:35 ... Most recent comment 2022-10-05 12:36:14
Acrylic Oil Paint Watercolor

​Hello dear experts,

I have a few questions about issues with various media when doing a thin underpainting layer for subsequent oil paint layers. I work on canvas board or wood, primed with acrylic ground.

1) I used thin watercolor-like washes of acrylics for a few pieces. Now I learned recently that the acrylics, even though they dry quickly, should be given at least three days before you paint over them with oils. I have not done that with the mentioned pieces, I went straight in with the oil paint once the acrylic paint was dry to the touch. So far (~2 years) I have not seen any issues with the paintings. Does that mean it is safe to work that way, or could strongly thinning the acrylics and/or not letting them dry for the recommended time cause issues down the road?

2) I have also experimented with water-miscible oil paint, and used it in the same way described above with the acrylics, thinned to a watercolor-like wash and painted over with oils once dry to the touch. Again, those pieces are fine after about the same ~2 years. I learned in the meantime that one shouldn't thin down oil paints to that degree, as that might cause an underbound paint film. My question here is, though the pieces are fine now, might issues arise down the road due to the underbound layer?

3) If I use watercolor as an underpainting, a few washes, how long would they need to dry before applying oil paint? And do I need to seal them somehow before that, or can I put the oils straight on top of the watercolor?

My basic concern is the longevity of the pieces. I don't care about them lasting for centuries, I just need them to be good for a few decades, so my clients can enjoy them in their lifetime. When doing underpaintings the way I described above, is it at all possible to estimate what kinds of issues might arise with the pieces, and how soon?

I apologize if any of this has been covered in the forums before, and I overlooked it. Thanks in advance for any help with these questions!

Clove oil usage in oil paintings

Question asked 2022-10-04 13:45:33 ... Most recent comment 2022-10-05 11:24:01
Oil Paint Drying Oils

First, I wish to thank MITRA for the useful answers to all sorts of painting questions. My question here is about clove oil usage in oil paint. I have read the previous discussions, and hoped for clarification or updates on what the conservationists or paint chemists think.

What percentage of clove oil added to paint will cause future solubility problems when cleaning or removing varnish? The Mark Carder paint and medium users have been told that some clove oil will not harm the paint; and that Mr. Carder had verified this with an unnamed expert.

I do not use clove oil at all, but then neither am I a purist in the sense that anything which has been shown to cause problems – frequently in undefined situations – should not be used.

Clove oil: will 1/10 of`% by volume hurt the paint? Etc.

With what solvents used in future varnish removals will the clove oil cause the most problems?

Can you give any citations to further explore?

Thank you.

Cleaning/restoration of old blueprints

Question asked 2022-09-30 02:08:56 ... Most recent comment 2022-10-03 11:36:14

​I'm wondering if q-tip + water would be a safe method for trying to remove small stains from old blueprints?  I'm assuming the blue pigment wouldn't be water soluble? These are small town high-school blueprints from the 1920s, so I'm guessing the quality of materials may not have been the best.

The stain almost looks like rust, so I'm not sure water will even touch it, but thought that might be a place to start.

Any other suggestions?​​

Oil painting smoke removal

Question asked 2022-09-25 10:18:35 ... Most recent comment 2022-09-26 11:10:04
Oil Paint

​I have a painting from someone that is a heavy smoker. The painting reeks of cigarette smoke. What can I do to remove this smell from an oil painting on canvas? The painting is approximately 25 years old. 

Canada balsam

Question asked 2022-09-16 14:26:09 ... Most recent comment 2022-09-19 19:00:10


I am interested in experimenting with straight Canada balsam as a varnish. The Getty Art & Architecture Thesaurus (link below) says that historically it "was found to bloom in moist conditions and darken with age."

My questions are: 1) Does the color darken to gray/black or to red? 2) What humidity level triggers blooming? 3)What would the treatment for bloom be?



Oil painting over gold leaf

Question asked 2022-09-13 17:44:05 ... Most recent comment 2022-09-14 10:52:13
Gilding Grounds / Priming Oil Paint Varnishes

​I will be painting over gold leaf. I'm working with 23.5k gold because I was told this doesn't tarnish and working on canvas.  Is it a good idea to varnish the gold leaf with a varnish like golden archival spray varnish then applying a layer of Gac200 to give the leaf some tooth before starting to paint over in oils? This should help with adhesion. Is there a better method for a more successful result? 

Gelatin and Yellowing

Question asked 2022-09-13 12:40:05 ... Most recent comment 2022-09-13 12:31:00

​Hello, Everyone,

I was interested in finding out whether or not gelatin in an aqueous solution (in and of itself) painted onto linen would cause yellowing over time or would it stabilize the linen?  My understanding with photographs that have gelatin on them that it is not, necessarily, the gelatin that causes the yellowing but the combination of the gelatin with the other chemicals.  

Also, would it be possible for this gelatin solution on linen (that is binding pigment) to "disappear" over time but cause the linen to dehydrate and darken --and where there is no remaining evidence of the liquid cementation between the interstices of the linen threads to evidence that gelatin had been there?  

Any help with this would be greatly appreciated!

Thank you,


Small hole in recently finished painting.

Question asked 2022-09-13 09:51:39 ... Most recent comment 2022-09-13 09:58:33
Art Conservation Topics

​Well, I’m in quite a pickle.  I have a buyer for a painting and discovered a flea-sized hole on the left edge right above the frame.  Which means I cannot easily access the hole from the back of the canvas.   And after research, it seems that patching is a poor option. Removing the canvas from the frame is something I could never attempt.   The buyer is stated she’d be happy if it was repaired or repainted, which I also can’t imagine having to do, lol. 

Surely there is some compund or glue I could gently use to fill in the area?   Because of where it's at repainting will be a breeze.  

Thanks in advance for any help!  tear 1.jpgtear 02.jpg

protecting outdoor vase

Question asked 2022-08-30 17:49:08 ... Most recent comment 2022-09-12 12:35:13
Art Conservation Topics Acrylic Environment Industrial and Non-Traditional Products Other Varnishes

I have repaired an outdoor vase (that had been vandalized), using mostly waterproof expoxies ( products).  I'd like to return this piece of artwork to its original location outdoors, in upstate NY.  My greatest concern is to weather-proof it against growth of algae, moss, mildews, etc. 

As you can see by the attached pics, the surface of the vase (which stands about five feet tall) is varied.  Some of it appears porous, some of it gives indication that the clay (I'm assuming) has been fired in a kiln, and some of it appears to have been treated with a “wash" (my layman's term for what looks like what it was treated with). 

You'll notice the chocolate brown-colored “scar" in the middle of the vase – this is the Apoxie product before it's sanded smooth.  Then it turns the gray color you see at the base of the neck near the top- that's where the most damage occurred.  All of the multi-colored, “mottled" parts – the light browns and various green hues – were present when I purchased the property the vase was on (2013).  I suspect this appearance occurred either during completion or as a product of outdoor weathering.

Ideally, I'd like to apply some type of “wash" to the entire exterior of the vase that would mimic the present mottling or at least render all of it of a somewhat uniform but random appearance – not necessarily a fully opaque coating.  My number one priority is to weatherproof the vase enough that it can be returned to the outdoors and not suffer the ill effects from exposure to the elements. 

Thoughts on how to proceed? Thank you.

permanence of oil on commercial oil paper

Question asked 2017-12-13 11:04:29 ... Most recent comment 2022-09-09 01:14:31
Flexible Supports

​I have been researching commercial, cotton, oil painting papers by D'Arches, Canson, etc, for detailed, preparatory studies that I may or may not mount and sell.  

Do you forsee any problems with 100% cotton papers by these or other companies?

The paper fibers are protected, according to their literature, but the OMS and oil can be drawn down below that surface somewhat, unlke the pH neutral PVA size layer tha I put on my papers before use.   Perhaps this affords more tooth for the paint layer to attach to.

Any thoughts?

Thank you.

PS   I avoid priming papers as I will thereby lose the very texture that I like in the paper, and have been sizing only.   Also, the investment in time and material makes them so "precious" that I may not be as likely to experiment with them.   I have followed the directions sent by Robert Gamblin some 15 years ago.


Question asked 2022-08-18 12:26:16 ... Most recent comment 2022-09-02 17:33:46
Animal Glue Egg Tempera Grounds / Priming Oil Paint Rigid Supports


My goal is about achieving impasto early onto ground so that I have it's reliefs more or less visible untill the end of painting. I would like to use traditional gesso ground on rigid support, apply that impasto if posssible and then painting in layers with oils.

Please, could I get opinions regarding two following koncepts that I have;

First - paint impasto strokes with traditional gesso (or distemper, I think it's the same thing) on traditional gesso?

Second - paint impasto strokes with tempera grassa on traditional gesso?

I know I could get maybe even better results with acryl or alkyd  ground/underpainting but my passion works best with more historical stuff.

Kind Regards,

Damir P.

Surface acrylic painting affected by insect excreta

Question asked 2022-09-02 10:49:00 ... Most recent comment 2022-09-02 10:33:00

Hi all,​

On a painting I sold a few years ago - with several finish layers of Golden Glazing Liquid - the owners found some tiny droppings from an insect/spider a few months ago.

I advised them to carefully remove it with a cotton swap (with a tiny bit of water). That worked well, but at one of the spots a tiny mark is still visible. It is hard to detect. 

Do you think this might cause further problems for the painting in the long term? Or would it be okay to leave it like it is?

Thank you!

Alternatives to GACs

Question asked 2022-08-28 18:16:04 ... Most recent comment 2022-08-30 13:08:01
Animal Glue Rigid Supports Sizes and Adhesives


Lately, Golden advises against using glossy acrylics in any preparatory layers for oils. In light of this, what would you substitute GAC 200 with? I'm using linen, stretch it first, size it, then add 2 layers of oil ground and last but not least I glue the dried canvas onto an aluminum panel with a PVA glue. I would like to have good oil blocking properties. I've been thinking about getting RSG, but I don't know how it can affect even a glued down canvas. It for sure will have less deleterious effect on the painting given the rigid support, but it can still soften (I think) and maybe move a little bit with very high humidity. PVA is another option but I've heard that it's not good at oil blocking. With regards to acrylic grounds, I'm a bit wary of using them in light of the recent findings regarding other types of acrylics. 

What would you size your canvas with before applying the oil ground?



oil plus wax solubility solvents.

Question asked 2022-08-19 15:19:06 ... Most recent comment 2022-08-19 16:48:49
Oil Paint

​Dear Mitra experts, how much wax can be added to a blob of paint until it turns the paint  solvent sensitive once dried?

And dammar?

Thank you in advance!

Glassine to archive watercolors and ink drawings

Question asked 2022-08-14 02:06:33 ... Most recent comment 2022-08-14 11:34:02
Art Conservation Topics

​Is glassine a safe paper to use as interleaving for watercolors and ink drawings? I have heard differing views on this. I have used it for a long time, and have never seen degradation, but recently I read that it should not be used for long term storage. And if not, what is a better paper for interleaving of these works on paper? Thank you in advance, I value all feedback.

Preparing wood panels for acrylics

Question asked 2022-08-11 16:17:47 ... Most recent comment 2022-08-11 21:37:59
Acrylic Grounds / Priming Sizes and Adhesives Rigid Supports Solvents and Thinners


I have a couple of questions about preparing wood panels for an Acrylic dispersion prime coat (Golden Gesso). I will ultimately be painting acrylics on top of the primed panels.

1. I have purchased the Zinsser bull’s-eye shellac (yellow label), But then spoke with a materials specialist at Golden and was recommended Midway Polyacrylic. Does you know if one is better than the other for a wooden panels? Can I use either with success to prevent checking and SID, while reducing warping due to changes in humidity? I have listed ingredients of both materials below. If neither would be appropriate, can you please recommend a consumer brand?

* I am no longer using GAC 100 or Gloss Medium to seal wood prior to acrylic dispersion. Recently, Golden came out with information stating that tiny cracks occurred through the acrylic dispersion when wood panels were coated with these materials. For most acrylic painters it is not significant, but I want flexibility and assurance that I’m not going to have fine cracks if I decide to paint thin layers in some areas of my painting.

2. The materials specialist I spoke with at Golden recommended a "spit coat" diluted with alcohol. Do you know what type of alcohol to use to dilute either brand and what the ratio would be for the spit coat? 


1. Bulls Eye shellac:

Ethanol, ISA propanol, methyl isobutyl, ketone, pure shellac, water

2. Minwax  polyacrylic: 

ISA propanol, 2 – Butoxethanol, dimethyl ether, Hydrated silica

Signing back of oil painting with acrylic paint?

Question asked 2022-08-10 15:40:18 ... Most recent comment 2022-08-10 17:09:13
Studio Tools and Tips Grounds / Priming Oil Paint Other Art Conservation Topics Acrylic

​I want to use a fluid acrylic paint to sign the back of oil paintings on linen and cotton canvas. I want to first paint a patch of fluid matte medium (I use Golden) or GAC ​on the unprimed back of the canvas, so that the brush will flow. My question is, could this cause the canvas to buckle or shrink unevenly in the long term? It is a patch about 1" x 2". I hope it would also prevent the fluid acrylic color from penetrating to the front of the paintngs. Or does this method present any other archival risks to the paintings? Thanks!


Question asked 2022-08-04 03:38:55 ... Most recent comment 2022-08-04 09:08:41

I'm looking for a varnish that can adhere to a surface that has been treated with wax.

It is in fact a sculpture made of polyester that has been finished with wax to give it a specific patina; the work will be placed outside and needs an extra coating to make it weather resistant and to keep its current appearance (UV resistant).

We are therefore looking for a matte varnish for outdoor use that can adhere to a surface consisting of wax / shoe polish, is UV and weather resistant and does not discolor (turns yellow) over the years.​

Thank you for your time and advice.

Kind regards,


Rabbit skin glue with vinyl

Question asked 2022-07-20 15:56:04 ... Most recent comment 2022-08-04 07:23:19


I have a friend who prepares his own traditional gesso but then adds vinyl to it. He says that it's fine to do so and that it makes the RSG a bit flexible. 

Is this a safe and compatible mixture?

Best Regards


Highliting Ink drawing

Question asked 2022-07-19 10:24:49 ... Most recent comment 2022-07-27 09:07:39
Ink Pen Pencil Watercolor Gouache Drawing Materials Chalk

​Hi dear people from Mitra.

I have a question regarding highlighting a ink drawing. The drawing is done with faber castel (ECO PIGMENT) permanent lightfast ink and is fully etched , also there are some wahes done in watercolor. However, some dark parts are a little bit too dark so i want to highlight them. Which medium do you think i can use over fully etched ink drawing ? gouache ? some pen highlighter, or a polychromos white pencil ? Please send your advices 

All the best 

Marko Karadjinovic

I am away from the internet until August 1st

Question asked 2022-07-13 13:09:32 ... Most recent comment 2022-07-21 11:54:40

​Dear all. My family and I are in the midst of a move and I will not really have access nor the time to respond to questions here. Sorry for any inconvenience.

Collage, sculpting, or molding: possible fillers and/or mediums?

Question asked 2022-07-13 08:10:11 ... Most recent comment 2022-07-13 16:30:33

​Hello All,

I'm in the think-tank stage of a new project. I want to create a (mono-chromatic) "painting" whose main visual interest will rely on the sculpting of a series of low relief images (think a modern version of Ghiberti's doors). It will be executed upon a number of small hardwood panels which, when assembled together, will create one large composite image, of say 3 1/2 feet x 5 1/2 feet or so. 

My main question is what should I use for my sculpting material? In the past I have tried:

Acrylic molding pastes (on HDF) are OK, but they dry too fast and I have found them to be both too coarse and way too heavy. 

I've done some low relief sculpting (on HDF) using traditional gesso (pastiglia). It was OK, but was very consuming to create even a small, subtly reliefed surface. 

I have created collages using pieces of fabric, attached to either plywood or MDF using a strong solution of hide glue.

Of the three collage is very good. I like it since it's lightweight and can be manipulated pretty quickly and easily. However, for low relief "sculpting" it's just a little too coarse and hard to control. So now I'm searching for a (thickening/filler) collage-type substance that might be added to an adhesive/medium which I could use for some low relief sculpting an image (or series of iamges). Thoughts anyone?

I've wondered about creating a putty using a recipe of sawdust and hide glue but I'm unsure for a number of reasons. Traditionally framers have used a substance called "compo" that appears to be an esoteric and toxic recipe of fillers, oils and resins

I'm currently conceiving of chopping up many small pieces of linen fabric, running them through a blender, and boiling them with baking soda to create a paste-like substance has traditionally been used to make rag content paper.

Egg tempera on watercolour/illustraion board

Question asked 2022-07-07 13:26:26 ... Most recent comment 2022-07-13 13:13:15
Egg Tempera Flexible Supports

​Has anyone tried using traditional egg tempera or tubed egg tempera on watercolour or illustration board?  If so, do you need to prime the surface with traditional gesso? Or, can you work directly on the surface?

Back of Paper Supports

Question asked 2022-06-20 08:11:48 ... Most recent comment 2022-06-20 08:05:00
Art Conservation Topics Drawing Materials Flexible Supports Grounds / Priming

​I'm a fan of coating the back of wood-based panels with housepaint, to protect them from moisture.  Is the same practice recommended for paper supports?  I'm thinking specifically of paper supports which have a ground on the front for metalpoint. I understand the weight of the paper is a consideration, and a very thin paper likely couldn't accept any paint without bleed through or warping.  But would a light coating of acrylic paint on, let's say, a 90 lb watermedia paper, and a more substantial layer of paint on a 300 lb paper, be a good idea?

Thanks, Koo Schadler

Gouache as under painting for egg tempera

Question asked 2022-06-17 08:51:14 ... Most recent comment 2022-06-17 13:49:24
Egg Tempera

​Hi, I've begun several gouache paintings on Aquabord  panels. I was wondering if I could finish them in egg tempera, painting over the gouache. Should I use an isolating layer of thinned egg yolk? Thank you!

Reflectivity of Silverpoint?

Question asked 2022-05-31 19:57:13 ... Most recent comment 2022-06-16 22:33:46
Drawing Materials Grounds / Priming Varnishes Acrylic

​Hello All,

I have just completed a project consisting of 64 panels, executed in silverpoint. After much experimentation and wonderful help from the moderators here, I decided to use Goldens's acrylic gesso (which I tinted with a home made melange of dry pigments to imitate terre verte) on HDF panels. These were then coated with two coats of (translucent) Golden's Pastel Ground. I chose Golden's Pastel Ground because it allowed for a fairly easily achieved 50 - 60% dark value as well as a tactile softness. For the highlights I introduced washes of titanium white acrylic. Overall, though the original subject matter contains some high contrast elements, the silverpoint versions of it that I have created have a whispy daguerrotype softness to them. Nice.

However, I have also noticed that in some of the areas where I made repeatred strokes of silver to achieve a darker value, there is now a glare or reflectivity element, depending upon the angle of my light source. I theorize that another coat of the (translucent) Golden's Pastel Ground on top of the silverpoint could be a good solution - because the toothiness it imparts would naturally diffuse the light. Is there any technical reason why I should not do this? Or alternatively, are there other fixatives or matt varnishes that might work just as well?

I should also add (just to complicate things) that I intend to cover the whole assemblage of these panels with some Liquitex (transparent) titanium white spray paint, in order to turn the realism of this soft daguerrotype into a more semi-abstracted image. The coverage of the spray paint will by no means be even, so the image can show through in places

So, if I were to use something (Golden's Pastel Ground or something else) to mitigate the reflectivity of the silver now, it would also need to function as the intermediate (matte) layer that it is and not function as a final varnish (which may very well come at the end, if needed, TBD).

Sorry for the complicated description. Strange how easy it is to visualize something but how difficult to describe it.

Thanks for any suggestions you all may have,


Ellen Trezevant

Using a drying oil to "fortify" a fresh painting.

Question asked 2022-06-07 02:59:30 ... Most recent comment 2022-06-15 17:42:42
Drying Oils Oil Paint Varnishes

​Good Day, I recently had the displeasure of varnishing a recently-completed painting, only for the retouch varnish to lift some paint. As I make a living from painting, it is not always feasible to give a painting months to dry. In this case, I was forced remove the offending varnish, as well the compromised paint layer, before repainting some patches that were lifted. My confidence was rattled. Once this fresh paint was touch-dry, I used a lint-free cloth to rub in some drying linseed oil (W&N) on to the surface. I left this oil to dry before varnishing, which proceeded without incident. This experience left me wanting to continue with this habit (rubbing some drying linseed oil on to recently-finished paintings before varnishing). I understand that my paintings will yellow, but as my color pallete tends to consist of yellowish earthy pigments, this does not bother me. My most harrowing experiences have always involved the varnishing process. Fortifying my paintings with linseed oil before varnishing would do wonders for my stress levels. W&N drying linseed oil seems to have "penetrative" qualities - I think it penetrates the paint instead of sitting on top. It is touch dry within a week. If I accept the yellowing, do you feel that I can continue this habit, or am I commiting a cardinal sin? Your advice would be greatly appreciated. Thank you for the work that you do.

Regards, Alex.​

starting points for oil colours and pigment surface area bibliography

Question asked 2022-06-13 04:10:15 ... Most recent comment 2022-06-13 03:56:00
Paint Making Pigments Oil Paint

​hello everyone,

I am looking for bibliography about the starting points (pigment - vehicle) for oil colours. 

Also, is there bibliography for pigment surface area per pigment?

It would be of much help if you could provide me with such information.

Thank you.

Grinding issue

Question asked 2022-06-03 21:24:59 ... Most recent comment 2022-06-05 13:25:52
Paint Mediums Oil Paint


I grind my own paints using the CPVC and a medium thats 50% linseed oil and a 50% polymerized linseed oil that doesnt have a low ph. 

My issue is that I glaze and i want to properly dilute my paint.  Some people tell me to dilute simply with oil, others with a 50% stand and 50% spike oil mixture and im sure there are many other ways. 

Is there a proper way that one can dilute the oil​ for glazing? Is there a math formula, like the CPVC formula ,in order to find out how much solvent can be used before it becomes unhealthy for the paint?  I ask this bc if there is i can use spike oil on it own in a safe way.  



Shipping/storing unvarnihed egg tempera paintings

Question asked 2020-12-11 09:27:16 ... Most recent comment 2022-06-02 15:55:42
Egg Tempera Storage Rigid Supports Handling and Transportation Art Conservation Topics

​Hey Mitra!

Does anyone have recommendations for shipping/storing unvarnished egg tempera paintings, especially regarding what material could touch the face of the work?

The works in question have been curing anywhere from 3 months to over a year. 

I considered glassine, but I imagine little creases or folds in the glassine could become abrasive. A thick poly was the other option I was thinking...

Always very grateful for the responses I get on this awesome forum. thanks - eli bornowsky

Sizing the back of paper for dried oil stick painting - Will it help?

Question asked 2022-05-20 13:06:56 ... Most recent comment 2022-06-01 08:19:16

Hi All,

Will applying a sizing like Fluid Matte Medium to the back of an oil stick painting on paper that had no initial sizing applied - help to mitigate the destruction of the paper fiber at all? Will it have any benefits for the integrity of the paper?

Thank you all very much for any advise.


Sizing the back of paper for dried oil stick painting - Will it help?

Question asked 2022-05-20 13:14:48 ... Most recent comment 2022-05-20 13:11:00
Sizes and Adhesives

Hi All,

Will applying a sizing like Fluid Matte Medium to the back of an oil stick painting on paper that had no initial sizing applied - help to mitigate the destruction of the paper fiber at all? Will it have any benefits for the integrity of the paper?

Thank you all very much for any advise.


(mods please delete untagged duplicate post. thanks)

Water Miscible Oil Paint

Question asked 2018-12-21 17:24:39 ... Most recent comment 2022-05-19 14:32:04
Drying Oils Oil Paint Solvents and Thinners

​I see recomendations for water miscible oil paint for ease of clean up and not using solvents.
Can you please comment on them from the viewpoint of longevity?

Ron Francis

Rabbit skin glue to prevent mould on canvas

Question asked 2022-04-30 12:37:45 ... Most recent comment 2022-05-16 16:17:12
Animal Glue


I have received a question I can't answer. I have checked the MITRA forums and resource guides.

Can we apply rabbit skin glue behind the canvas to prevent mold growth?

Does anyone know? Thanks.

Convert oil primed panel to true gesso panel?

Question asked 2022-04-27 10:42:11 ... Most recent comment 2022-05-04 10:53:36
Grounds / Priming

20 Years ago I prepared 9 gessoed panels, 24" square, but I never used them. I brought them out of storage yesterday to use for my paintings that are generally gouache/tempera paint on a true gesso surface. (Not egg tempera). The problem is that my memory that the panels were true gesso over rabbit skin glue (RSG) was incorrect. In fact the panels are 1/2" birch ply on 3/4" pine frames (they are very rigid) that are gessoed with an "oil priming white" surface. I don't recall the brand of oil priming. I usually bought high quality materials. The surface is quite smooth, but not without some "tooth". If I recall I usually sized the wood panel first with several layers of RSG, it was a common practice in my art school, though frankly don't know if that's a correct method. (Ralph Mayers book was bible at my school so although I havent looked at it recently I presume I followed a procedure from that source.) I prefer to paint gouache/tempera on a true gesso surface because of the absorptive qualities. (I generally paint in washes, or with a more fluid rather than thick paint, as per another forum thread.)

My questions:

1.  Can one even paint with gouache/water tempera paint on an oil primed surface, albeit 20 years cured? It seems to violate "lean to fat" rules...

2. Can I "convert" the oil primed surface to true gesso? 

        a. Can I apply an intermediate layer of RSG then several layers of true gesso? If so would increasing the "tooth" by sanding with 220 grit or so help? Thoughts?

        b.  Or perhaps shellac? With whatever intermediate steps you think appropriate? Is shellac an ok ground for a true gesso surface? With RSG between?  etc etc

     c.  Is there some other way to "convert" the panels and retain long term stability?

3.  Does anybody want to buy 9 beautiful oil primed surfaces?     


Thanks so much! I'm new to the forum and love the nerdiness. I love the deep dive!


Alternatives to Aluminum for housing paper artifcats?

Question asked 2022-04-23 13:35:20 ... Most recent comment 2022-04-27 16:31:20

​I'm not an art conservationist, but I'd like to build decorative box for paper cards to be stored on and around wooden shelves.  I was planning to 3D print out of aluminum because of its acid vapor blocking properties. 

However, it would be cheaper and prettier to use Pewter or Zinc, which I can cast at home. 

But I wonder if Zinc or Pewter will still be able to block the acid from the wood? Or perhaps when Zinc or Pewter oxidize they release their own acid? 

I can't find anything on google about this topic. If anyone can provide any articles or information on the topic I would be so grateful​! 

Sealing a Panel Before Stretching Fabric Over it

Question asked 2022-04-26 19:27:09 ... Most recent comment 2022-04-27 10:18:26
Rigid Supports

​I am preparing cradled linen panels. My  panels are made of 3mm Russian Baltic birch plywood and cradles are made of kiln dried grade A clear pine, or basswood or Russian Baltic birch plywood. If I stretch my sized linen over cradled panels, then coat it with acrylic dispersion ground (Golden) several times, what would the likelihood of the cradled wood panel warping be, if the cradled panel is just left unsealed?  If I needed to seal it, what would be the best non-toxic process to seal it before stretching? 

Sennelier Mediume Fluide Brilliant

Question asked 2022-04-19 13:50:29 ... Most recent comment 2022-04-26 22:17:43

​Concerning use of Sennelier's painting medium Medium Fluide Brilliant with acrylic paints, usually also Sennelier, but occasionally with acrylics of other manufacturers. Questions: How far may the medium be diluted with water before it is too diluted to form a reliable film?  I am thinking especially of the case of using the acrylic more as a tinting medium, highly diluted, for the Fluide than for the acrylic's own binding properties.  What is the medium's degree of permanence? Are there any pigments or paint dyes used in acrylics that are to be avoided when using it? Are there any other cautions for its use? Its handling characteristics and its transformation time from tacky to hard seem distinct from other acrylic mediums; is its composition significantly different from others?

How to proceed

Question asked 2022-04-05 13:15:10 ... Most recent comment 2022-04-07 17:20:15
Health and Safety Environment Art Conservation Topics Scientific Analysis

​hi. I have been working on an oil painting commission. I set it aside to let the top layer dry a bit before continuing on to the final details. When I came back to it, there were these sticky droplet looking things all over it. I cannot figure out what they are or where they came from. I'll include photos, but I couldn't get very good ones. At first I thought it was possibly the canvas panel I bought, but there is some on the easel behind it. I did have a fly in the studio. Perhaps it landed on the panel and walked around leaving something sticky. Without knowing what the substance is, I'm unsure of what to do to proceed. Is it safe to paint over?  Should I use gamsol or some other substance to remove it?  Should I worry about chemical interactions since I am unsure what it is? I am nearly done, so starting over isn't an appealing option. Sticky drop.jpeg

An oil-based primer that dries quickly and doesn't yellow

Question asked 2021-07-12 09:02:13 ... Most recent comment 2022-04-05 11:10:41
Oil Paint


I have come across an Austrailian brand of oil primer that appears to utilise water-miscable linseed oil because it is dilutable with water. It is fast-drying so that you can apply two coats in one day and paint in oils on the following day, possibly because of alkyd resin content. But since it contains linseed oil I don't understand how it can be applied as they say, with no size. They say this oil primer can be applied directly to the canvas. They also say it doesn't yellow.

Does anyone have any ideas about this?

Water affecting acrylic sheen on dried paint

Question asked 2022-03-30 13:14:22 ... Most recent comment 2022-04-04 14:52:22
Acrylic Scientific Analysis

I recently did a test where I used a test swatch which consisted of normal thickness brushstroke of student grade acrylic (no added mediums or retarders). This has been left to dry for at least 3 months. I then brushed onto the very dried surface some normal cool tap water and let it absorb/evaporate over 3 days.

After this when I checked the test swatch I noticed that at the edge of the water affected area the surface of the paint was now more shiny than before (more of a gloss finish compared to the satin previously). It's a bit like the water ring you get on paper how it alters the lock of the paper.

My question is what is happening here? Has the acrylic paint film expanded slightly with the water and has settled back in a slightly smoother layer (thus affecting the sheen). If not this then do you know why the tap water is affecting the acrylic paint film like this? And if it has any implications for conservation / using water with acrylic on multiple layers?

Richard Phipps


Question asked 2022-04-03 13:58:46 ... Most recent comment 2022-04-03 16:41:55
Egg Tempera Pigments Solvents and Thinners Varnishes


Please can you help me with following notion.

I just ordered Paraloid B72 in ethyl acetate from Kremer to isolate lean egg tempera (ET) prior to oil glazes and realise I don't know it's ph value. SDS states N/A. Pure ethyl acetate SDS also, while acetone states ph: 5 - 6 (0 mg/cm3; 20°C).

Why I ask this? Is solvent ph​​ important since my ET has synthetic ultramarine pigment which we know to be not compatible with acids? 

One conservator answered me that ethyl acetate is very litle acidic and would evaporate fast so there shouldn't be problem with that plas also that binder would protect it.

I would like to get second opinion.

Kind regards,

Damir P.

Zinc Soaps

Question asked 2022-03-18 14:09:55 ... Most recent comment 2022-03-20 15:31:42
Art Conservation Topics Oil Paint Scientific Analysis Technical Art History

Darkening umbers in oil?

Question asked 2022-03-16 16:02:41 ... Most recent comment 2022-03-18 20:09:29
Drying Oils Pigments Oil Paint

​From time to time one comes across past authorities advising not to use raw or burnt umber as they darken more than mixtures of ivory black and ochre.  Such advice seems largely absent this century.  Was it false?  Were the umbers of the first half of the twenthieth a different beast?  Is it just the high oil content of umbers.  Did they or do they, have migrating micro particles?  One source I read, claimed that underpainting darkening seemed to be blocked in areas covered by thin layers of lead white. 

Interested in all your views.


Zinc - Direct Process vs Indirect Process

Question asked 2021-12-13 00:10:27 ... Most recent comment 2022-03-08 16:59:16
Art Conservation Topics Oil Paint Pigments

My question: What research has been done on saponification of zinc production differences between Direct Proces & Indirect Process as discussed in this paper? Has this been explored and if so where are the findings? Has anyone in the oft-quoted zinc research made a distinction between zinc manufactured using the two different processes?

I'm not advocating use of zinc, I'm asking if this finding has been explored because good science should always question things. It's from 1949, I would assume it has been accounted for but found nothing.

Let me share Antonin's post from WetCanvas earlier this year re differences in condition of various paintings that used zinc:

Have you seen this paper regarding the changes in the way zinc oxide pigment was made during and after WWII?  The original Chinese White introduced as a watercolor in 1834 was Acicular Zinc White.  The current best quality Zinc White is Green Seal French Process which is much finer “irregularly shaped particles of uniform size distribution”

Here are some excerpts:

“The Victorian Branch of the Oil and Colour Chemists’ Association held a meeting in Melbourne, Australia in the summer of 1949 to discuss a sudden and marked increase in problems associated with house paint formulations containing zinc oxide pigment, and to investigate any possible relationship between this increased failure rate and recent changes in manufacturing methods for the pigment.

C.H.Z. Woinarski, then Senior Chemist at Hardie Trading Ltd., outlined the shift in paint production and performance observed during World War II, when new methods of pigment manufacture emerged—at newly built or converted facilities—to meet an increased demand for zinc oxide pigment. Direct Process (also called American Process) methods of pigment production were replaced by Indirect Process (sometimes called French Process) methods, and this manufacturing shift was accompanied by a precipitous rise in failure rates of oil‐based house paints containing zinc oxide pigment produced using the new method.

Nelson confirms that Direct Process oxides contained various percentages of acicular variations on the crystalline form, some joined to form “twins” and “threelings” (referred to as “brush‐heap” formations by Bussell), while Indirect Process zinc oxides (often marketed under the term “Seal” oxides) were typically irregularly shaped particles of uniform size distribution.

Research from the University of Stuttgart built on rubber industry literature citing a possible link between the oil and resin vehicle and swelling behavior in zinc oxide paint films (Funke 1967), and related tests by Morley‐Smith on the influence of fatty acids in zinc oxide reactivity suggested that soap formation slowed with increasing acid chain length, and noted that “a marked difference was apparent between the behavior of the saturated and unsaturated acids, unsaturation reducing the rate of soap formation appreciably”.”

(Link to paper from above was here)

So the much admired condition of Pre-Raphaelite painting may be due to the less reactive, larger acicular particles of the Zinc White pigment then available, and the use of long-chain, acidic, cooked oil/Copal mediums that reduced “the rate of soap formation appreciably”.  The thin layer of Zinc White the PR masters painted into was thinned with Copal (or Amber) medium.

The painting mediums commonly used by British 19th century painters were cooked oil/Copal mediums (art suppliers obtained this from British coach varnish manufacturers) or the popular Roberson medium that was made with leaded drying oil (linseed oil cooked with litharge), heavy Mastic varnish and Copal coach varnish.

Phthalocyanine migration through dry oil paint.

Question asked 2022-03-04 17:52:28 ... Most recent comment 2022-03-05 09:54:31
Oil Paint Dyes Pigments

I've just read a claim that Phthalocyanine migrates through dried oil paint. (Virgil Elliot's facebook group.)
Is there any credibility to this claim?
I have not heard of this before, nor experienced it in over 40 years of working with it, but as an admin of the group, I would like to respond to the comment with more than my personal experience.

Also, is Phthalo classified as a dye?

Thanks in advance
Ron Francis.

repair "family crest" bought in 1966 London, paint is dripping

Question asked 2022-02-15 15:44:56 ... Most recent comment 2022-02-16 12:07:59
Other Art Conservation Topics Paint Mediums

​A client asked me to repair a family crest he bought or had made in London in 1966. Some of the paint is dripping -- not sagging. It looks like thick liquid paint dripped a few inches. 

There are areas on the surface where the paint is tacky but most areas are smooth.

My understanding is that the dripping happened in recent years after he moved it to his house. The object does get direct sunlight so my guess is that heat has caused the problem. 

​I did some solvent tests to try to figure out what kind of paint was used -- Isopropyl Alchohol dissolves the paint fairly easily so I removed all the dripped paint though a combination of cutting the thick drips away and then using the alchohol to remove the rest. 

​I have a limited amount of time that I can spend on this due to his budget and have already applied a fresh layer of acrylic over an area that I removed the dripped paint. 

My questions are: 

1. Is my plan to overpaint with acrylic artist paint ok for this purpose? (I use Golden acrylic for my own work.)  

2. should I varnish, and if so what kind of varnish would be best since I don't know for sure what kind of original paint was used. I have both MSA and Polymer varnish from Golden.

3. is there anything I can do about the tacky areas or should I remove those areas and repaint them also.

4. any ideas on what caused the paint to drip and how he could avoid this in the future? (I will advise him to keep it out of the sun!)

The paint looks like enamel paint and the object looks like it may have been a sort of tourist purchase. I don't have much of a budget for this project,so I need to do the best I can in 3-4 hours. I am a painter, not a conservator.

Some more information about this piece:

The painted plaque has relief decorations and is mounted on wood with screws through the back.  It appears to be some sort of thin plastic molded over a thin piece of flat wood, with the hollow areas filled with a dark brown resin like substance that looks dry and porous.

thanks for any insights, suggestions, advice!

Wyeth's Painting Problems

Question asked 2022-02-09 14:55:55 ... Most recent comment 2022-02-11 08:35:46
Egg Tempera

A fellow tempera painter recently made me aware that Wyeth's painting, Groundhog Day, is displayed at the Philadelphia Museum of Art under a plexiglass box because it's flaking off in parts. While Wyeth was an artistic genius in his handling of egg tempera and design/compositional abilities, he was not, as Dr. Stoner has noted previously on this forum, "a stickler for technique". (see I can think of many reasons his paintings might peel (uncertain ground, uncertain tempering, working on an aged paint film, adding ingredients like leaves and mud to the paint - he did all of the above!), but conservators are there is to address a great artist's idiosyncrasies. If the painting is visibly peeling, it's hard to imagine a major museum wouldn't attend to it.  Is it a matter of not enough resources (a perennial issue for museums, I'm sure), or no trained egg tempera conservator on staff, or....?  Thoughts?

Koo Schadler

Rabbit Skin Glue

Question asked 2022-02-04 09:43:11 ... Most recent comment 2022-02-08 15:15:20
Animal Glue Grounds / Priming Sizes and Adhesives

​Hello All

Some questions:

1.  In discussions on an egg tempera forum, the topic of rabbit skin glue (RSG) has come up.  I note on the forum that the term has come to more broadly denote a collagen-based, high bloom strength, high quailty glue that doesn't necessarily come from rabbits, possibly from cows and pigs (as on the MITRA adhesive handout, and as I've heard from material experts); and that if one wants to work with actual RSG, look for the term "genuine" and read the technical data sheet.  A European-based commentor on the forum says the term isn't used in this general way in Europe because of EU labeling laws; if a glue sold in Europe is labeld RSG, it's from rabbits.  So I'm wondering, is the ambiguity over glue nomenclature just in the US, or is it a broader issue?

2. My understanding is that animal glue in a ground should be very strong because grounds are essntially high PVC paints that need a strong binder to hold all those solids together - yes?  Is it accurate that the source of a glue (rabbit, cow, bovine) isn't critical; more important is that a glue be derived from collagen and have a high bloom strength?  (Brian, I've noted your insightful comment that 'rabbit skin' wasn't even used in painting manuals prior to the 19th c.)

3.  I've asked this question before but it went unanswered, so I'll try again: does anyone know what constitutes a high bloom strength?  Is 300 considered high? (Personally, I prefer the 450 range).  

4.  Looking at a few suppliers websites, I note that "genuine" RSGs tend to have a bloom strength in the 300s; whereas more ambiguous RSGs (not labeled genuine, technical data sheet says more generally "from animal collagen") tend to have higher bloom strengths.  Do genuine RSGs have a lower bloom strength than glues from cows and pigs?  If so, are cow and pigs glues better for gesso than genuine rabbit skins?  

Thanks for any light you can shed on these questions.

Koo Schadler

Salt technique in watercolour

Question asked 2022-01-31 06:03:17 ... Most recent comment 2022-02-07 04:07:30

​Hello. I have been asked if the popular salt technique in watercolour painting causes damage to the paper. The method involves dropping fine or coarse table salt on wet watercolour paint to remove spots of paint by absorbing it. When the painting is dry, the salt is brushed off leaving speckles of white paper. It is not a new technique, it has been used for decades.

Does anyone know if the residual salt in the paper poses a risk of degredation?

I checked the forum and couldn't find anything covering this topic.

HDF hardboard support for egg tempera

Question asked 2022-01-23 14:43:58 ... Most recent comment 2022-01-28 13:39:13
Egg Tempera

​Hello MITRA,

I used HDF hardboards supports for my paintings (egg tempera on homemade true gesso). I read that it is good to choose a more than1/8 inch thick panel. Since I am having a hard time finding 1/2 inch HDF at my local hardware store, I thought I could glue two 1/4 inch panels back to back using regular wooden glue or white glue. My painting sizes would vary between 5 x 7 inches and 2 x 2 feet. Do you think it would be an appropriate choice, or would the moisture accumulated in the gesso would eventually make the two panels split (I put between 8 and 9 gesso coats on each side and back of my panels)?

Thanks  for you help!



Painting on a very dried oil painting

Question asked 2021-12-23 20:18:18 ... Most recent comment 2022-01-19 10:37:18

​Could I please get your thoughts on best practice for layering oil paint? I hear about and have experienced myself, lots of problems with adhesion and I understand that using retouching varnish between layers and oiling out of the whole surface are both not recommended solutions. I love layering and often will continue on a painting after it is very dry. Oiling out doesn't work in this situation for me anyway as it beads up and also I don't want a yellow surface where some parts will not be covered.​ I have tried 'etching' the surface with turpentine or oil of spike lavender as they have strong bites, but it doesn't work. After the paint has dried for a few weeks I can easily scratch it off with a fingernail. The best solution I have found to allow a bond is onion juice. But it doesn't always work. 

I have heard of sanding but that seems drastic and wouldn't get in crevices. Is there anything that works consistently to allow you to continue painting on a closed surface?

Thank you. 

Unbound pigment due to solvent use

Question asked 2022-01-14 19:31:02 ... Most recent comment 2022-01-19 10:32:37
Oil Paint Varnishes Solvents and Thinners Art Conservation Topics

About to varnish oil on panel large seascape/ coastal rocks painting that took me many months due to high level of detail. Yes, waited six months. This is a major work for me. Discovered in spot cleaning with cotton bud and saliva that with a decent rub pigment lifts off in places. A light rub doesn't really remove much at all. I did use solvent in some places to thin paint (following example of well-known Youtube artist) - it was prior to me setting out to learn about good painting practice.

Looking for advice in terms of pros/cons for next steps. Life isn't black and white, complexities with pros and cons make sense and are welcome.


Oil out: Risk of yellowing. I assume dark yellowing less a concern if kept in well-lighted situation. Also, good oiling out requires rubbing back which may move/remove the pigment anyway. 

Varnish: Just varnish it - which will bind loose pigment to varnish and create problem later. Perhaps put note on back indicating risk of pigment loss. My plan is gamvar which I was going to brush on. I'm suspecting better to buy a spray? I want gloss and haven't used sprays - recommendations helpful.

Other: No idea. I don't want to act until I have the best options on the table.

Whiteness of polyester canvas

Question asked 2022-01-06 00:06:31 ... Most recent comment 2022-01-06 10:51:48
Grounds / Priming Flexible Supports Acrylic


I'm currently painting with acrylics on polyester. The paint sticks beautifully. I've noticed that the polyester cloth is much whiter than my titanium white paints/primers. Compared to the fabric, titanium looks darker and yellowish. Maybe the material contains some optical brighteners - I'll try to find out.

​I'd like to utilise this cool white cloth for bluish paintings. I need to prime the surface to even out the texture - but any pigmented primer would kill that whiteness. I'm thinking of preparing the surface with a clear primer, thus preserving the expressive tone of white. I quite like the matteness of Amsterdam Heavy Gel Medium. If I prime with it, will it yellow over the years?

Thank you!

Oil leached out from a passage onto surrounding underpainting

Question asked 2021-12-15 14:41:53 ... Most recent comment 2021-12-23 01:53:38
Oil Paint

I am reposting my latest question since I now have a new issue, previously discussed under the thread about white-looking filmy rings of presumed impurities that were brought up by cleaning an in-progress painting with artist's rectified turpentine then wiping again with OMS to remove any turps residue. I have another strange issue with the same painting that I think must have also been caused by cleaning it with turps.

This happened as I painted a passage two weeks ago in the area I had previously wiped-down (long evaporated), which to recap was a mechanically-thin underpainting on acrylic dispersion primer. I'm using professional grade oils suspended in walnut oil, with a walnut oil/alkyd medium. The underpainting was done several years ago using a different brand of solvent-based alkyd medium, mixed 50/50 with OMS. In my second, current layer on this underpainting, I'm using a 60/40 fatter ratio, and in both layers, the paint is adulterated 20% with my medium mixtures. The substrate is high quality, stretched linen canvas, and if it makes a difference, my studio relative humidity percentage was really low when I last painted (in the mid to high 20s) with a temperature of 72F.

I've been working on this piece for several months with no issues until I wiped the lower part of the painting with the turpentine as I mentioned previously. It's a huge canvas, so I have to paint one manageable area at a time. What happened recently is the first time I've ever seen anything like this happen in the several decades that I've been painting in oil paints. I noticed after I had completed this particular passage that the walnut oil was leaching out in a thin ring around the edges, as one might see had it been placed on paper or a paper palette. It happened both onto the adjoining underpainting and the adjoining long-dry area with a second layer at 60/40 (the green grass in the attached photo). I knew it would be bad to leave a "bare" unpigmented oil edge like that, so the only thing I could think of to do was to wipe that oily edge off with my lint-free rag with OMS, then retouch the edges of the areas so they weren't inadvertently too lean. I kept having to work back and forth until it wasn't leaching out anymore. There were a couple of places where I was never able to reapply paint on the edge without it continuing to leach, but I was wiping very carefully, so I don't expect it to be too lean at the edge.

Unfortunately, when I returned to the studio this week, I discovered that the leaching may have continued in a few spots. It's hard to tell, since I do see a darker outline, but it doesn't look as shiny as the main passage. I know if I overpaint unpigmented oil that it could cause adhesion issues, but it I leave the areas that they can discolor over time, so I wondered about carefully sanding these edges? It's the only thing I can think of, so I welcome your expertise.

When I was painting this passage, I recall feeling that when the brushes went down, the surface had a different "drag" to it, an almost "squeaky" feeling, so I suspect that somehow, by using the turps, I disrupted the oil layer of the underpainting, though it is definitely not underbound. Would oiling out the next area before painting each new passage take care of this? I don't usually oil out as I work, and I know you have to paint over it lest it turn brown eventually if left bare. If this is the solution, I'm also wondering if this would be enough oil to affect my fat-over-lean ratio. Since it is difficult to always predict what organic shapes my textures will take in each segment of working on this huge canvas, I'm a little concerned about oiling out, unless it isn't as difficult to manage properly as I am thinking.

I don't yet know if the grass areas with the previously discussed subtle white filmy rings of impurities that also resulted from this turps application will behave in this same way. I really hope not! And just to dot the I and cross the T, did you think that I'd be able to overpaint those affected areas with highlights and shadows without those presumed impurities coming up to haunt me later?

So my three questions are: 1) how to continue painting the areas near the passage that leached oil to keep the leaching from happening again, 2) how to handle the now-dry areas of presumed oil outlines that look like they continued to leach from this passage after I left the studio, and 3) if I can overpaint the areas where white filmy impurities were brought up by turps.

I'm attaching a few photos of this oil leaching situation that were taken prior to my efforts to correct the situation. It looks like a darker gray pencil line of sorts. I haven't been able to find anything about this phenomenon, so I can't tell you how much I appreciate your help. This is a very large work for which I have received grants and have a deadline, so for both financial and time reasons, starting over isn't an option.

Many thanks!


oil painting on a rigid support

Question asked 2021-12-17 15:30:39 ... Most recent comment 2021-12-20 15:10:48


I have read all the posts about oil painting on a rigid support and all of your resource guides. 

I am writing an article about permanent paintings and wanted to illustrate it with some images of aged and cracked paintings so I went to the National Gallery in London today. What I found surprised me and I wanted to ask what you on the forum think.

It is widely accepted as best practice that painting on a rigid support is better than on stretched canvas. And that canvas glued to a rigid support is best of all, as it can be removed from the panel at a later date if the wood becomes a problem.

But the oil on panel and oil on canvas paintings I saw today tell a different story. I know that they are kept in better conditions than your average studio, but none were behind glass and they ranged in age from 650 to 150 years old. Andt they must have lived in a studio, then a house, maybe a commercial gallery, then been transported, all in different environments, before ending up being pampered at the museum. And very few of the canvases had crazing, while many more of the panels did. I know nothing about the different kinds of cracking/crazing of paint or varnish. I am referring to the jagged, dry riverbed, dark fine lines usually visible across light areas. The cracking seemed more to be predicted by the painter than by the support. No Titian or Veronese paintings on canvas are visibly cracked anywhere, Coreggio on canvas was consistently cracked. This makes me think it was down to the painting mediums they used, rather than the support.

Just as surprising was seeing the paintings of the 1800s with thick and layered oil paint on canvas and none of them were cracked. I understood that a thin layer of paint was better than a thick one and that a thin alla prima was best of all, because layering is problematic. These are both thick and layered and only Suerat's enormous bathers painting had a couple of cracks.

The panels with cracking/crazing also sometimes had large raised cracks coming in from the top edge, that I assume are between slats of wood, but they don't always seem parallel. But they also had more of the cracking across the light areas, usually flesh tones. They were the oldest paintings though, from around 1500.  

The size of the canvas didn't seem to matter, some enormous Titians on canvas are crack-free. Now, it could be that it isn't stretched canvas but rather mounted canvas. But the text on the wall seems to say when it is mounted, and these didn't. And in a few cases you can see the cross bar imprints.

So I wanted to check that the 6 claims I am about to make in my article on creating permanent paintings are accurate. These are the very short summaries.

  • A rigid support is better than a flexible surface
  • Alla Prima is better than layers
  • A thin layer is better than a thick layer
  • Use oil paint with fewer ingredients
  • Add few or no mediums
  • Varnish after 6-12 months
Any help is gratefully received. Thank you!

an additional reason to varnish

Question asked 2021-12-15 21:12:10 ... Most recent comment 2021-12-15 22:50:56
Oil Paint Varnishes

​An experienced art tutor once mentioned in a video a few years ago that in addition to the other reasons to varnish an oil painting (protection from scratches, to be removable when dirty, to deepen the saturation, to even out the sheen or change it) that you wanted to varnish an oil painting after it was completely dry in order to seal the painting to prevent it from absorbing any more oxygen after this point - because it would become overly oxidised or dried out if it continued absorbing forever.

Is this correct?


Artist's rectified turpentine caused white "rings" on my oil painting

Question asked 2021-10-22 01:07:38 ... Most recent comment 2021-12-11 05:33:29
Oil Paint Solvents and Thinners

​Hi MITRA, 20211022_005347.jpg

I began a large oil on linen several years ago, and picked it back up again when I received grant funds to complete the project.

In a case of "what's done is done", since I'd had good luck in the past with cleaning spots/stains off of an in-progress painting with artist's recified turpentine then cleaning off any potential residue with OMS, that was the approach I took earlier this week on one area of this painting. As soon as the solvents dried, I saw a faint white residue that was comprised of many whitish "rings." I had used a freshly-laundered rag that had previously been used for oil painting, so I came back in with another treatment of OMS and a new clean rag, thinking that perhaps a thin veneer of oil that made it through the laundering process had been deposited by the rag. It got a little better (and when the surface was wet with OMS it looked fine), but once the OMS dried, the rings were still there. It kind of looks like a patterned version of sinking in. I wondered if something migrated up, or if I disturbed the binder too much, etc when I cleaned the surface with the turps? 

I use a high-quality paint with a walnut oil binder, so there shouldn't be any impurities in the paint itself. I also follow the fat-over-lean rules, and never adulterate my paint more than 20%. I had started this work with a solvent-based alkyd oil medium, then switched to the walnut alkyd oil medium, though the affected area is comprised of just a couple of layers with the original medium. I do plan to overpaint, though I had been planning to just add highlights and shadows to this region rather than overpaint the entire area -- though if that's what I need to now do, I will. I'm also wondering if varnishing later will take care of it?

I've attached a photograph for your reference. It looks like the whitish shapes settled into texture made by the hand-applied acrylic dispersion primer "gesso", because the paint layers themselves are fairly smooth and applied mechanically thin. (Incidentally, this surface texture is only visible by zooming in on the photo -- it isn't apparent to the naked eye or touch -- and it seems like if the turps bit into the paint layer enough to create the texture, that it would either have revealed the underpainting or the white primer.)

This particular painting is part of a larger project for which I have a deadline. It is a very large canvas, so for both monetary and time reasons, starting over isn't an option. I definitely hope that you won't think it is necessary. 

Thanks in advance for your help and advice. I do hope you'll have good news for me and that this won't cause any adhesion problems down the road. Fingers crossed that it is easily remedied.

Preservatives for making watercolor paint?

Question asked 2021-11-26 12:50:55 ... Most recent comment 2021-11-29 16:31:49
Watercolor Paint Making Paint Additives

​I have been making my own watercolor paint and have had a problem with mold growing on some colors.  

What are some preservatives that I could add to my paint to prevent mold growth?

Methyl Cellulose

Question asked 2021-11-15 07:27:40 ... Most recent comment 2021-11-19 05:34:01
Animal Glue Grounds / Priming

​There is a 'vegan' traditional gesso for sale (see​) that uses Methyl Cellulose as a binder.  I've looked online for the gel strength of methyl cellulose; it seems to vary but I see mention of a high strength version, although I couldn't figure out specifically what that strength is.  A strong glue is important in a ground and I'm skeptical that cellulose is an adequate replacement for animal glue, but I don't know that for sure.  Any thoughts on how strong a binder methyl cellulose is?  

Thanks, Koo Schadler

Eucaboard panel

Question asked 2021-10-26 07:55:55 ... Most recent comment 2021-11-11 20:49:30
Rigid Supports

​We recently got a question on the use of eucaboard instead of the (currently often) unavailable standard (untempered) Masonite. It seems to be a new material that we are not familiar with. From our research, it appears to be a eucalyptus-based alternative, similar to Masonite, so one may need to consider using a SID blocker on top of the Eucaboard before painting with acrylics. Do you have experience with this product or any hints on its long-term stability? 

Panel that is bowing

Question asked 2021-11-01 17:07:40 ... Most recent comment 2021-11-07 01:02:07
Oil Paint

​A painting I created before I knew about sealing wood with GAC100 (now Gloss Medium), is starting to bow. The bowing is slight. The panel was pre-primed with acrylic gesso. I created the underpainting with acrylic paint mixed with matte medium, allowed it to dry for a week, then applied alla prima oils. This painting was varnished about 9 months after it was painted with a mix of satin and gloss Gamvar, (50% - 50%). 

This painting was created in 2019 and has been displayed in a home with air conditioning and heat. There is humidity. The bowing has just begun and is slight. It's hard to photograph, but I'm told it's a bit more than I can even see in the photo. 

As I know now that I should be sealing the panels (and probably not using pre-made panels so I can seal under the acrylic primer too), is there anything that can be done to this painting to make the wood settle back to normal?

Thank you! thanks 

Egg Tempera Marouflage?

Question asked 2021-10-27 12:28:41 ... Most recent comment 2021-11-03 12:26:51
Egg Tempera Flexible Supports Mural Painting Grounds / Priming

​I have experience with marouflage (painting on canvas, then adhering to the wall) murals with acrylic. I greatly prefer egg tempera to acrylic in almost every respect. Is egg tempera an option for marouflage? In my initial tests, it seems to adhere to the canvas well (Caravaggio #504, acrylic-primed 100% polyester) and remains flexible, initially at least. I know egg tempera does get brittle with age, but I'm not familiar to what extent, since I've only ever painted on gessoed wood panels. 

If I paint a large canvas with egg tempera, roll it up, and install it within a month or two, will the paint crack, be damaged, and/or delaminate? What is the window that egg tempera becomes brittle? Of course, if the mural is removed decades down the road, that would be a different story. I do realize this is breaking all the rules of egg tempera (painting on an acrylic flexible ground, and rolling it up to boot), but I thought it's worth the experiment and reaching out to experts because I love painting with egg tempera and want to avoid acrylic if at all possible. I should also mention, these murals are only interior.

The benefit of marouflage is being able to paint in my home studio in ideal conditions rather than spending extensive time on the road. I prefer marouflage when I'm asked to paint murals on latex-primed drywall since the canvas will outlive the gypsum board (which seems like a temporary material to me).

A somewhat related anecdote. I have heard of Serbian mural painters using marouflage on a plastered canvas, painting with silicate paints, rolling the canvas, and installing it. The experts at Beeck mineral paints said they have heard of this, and of course it is not a best practice since it would develop cracks (at least microscpoically) that may or may not be an issue in an interior setting, but would definitely not survive outdoor elements. They encouraged me to experiment, and recommened one of their primers. Would a siliceous primer be better ground than acrylic? Or how would a thin coat of true gesso fare on a rolled canvas? 

​Thoughts? Thanks for entertaining my musings!

-Brian Whirledge​​

Transfer a drawing on a true gesso panel

Question asked 2021-10-26 14:48:38 ... Most recent comment 2021-11-01 14:52:22
Egg Tempera

​Hello MITRA,

I have a question about transfering a drawing on a true gesso panel. 

Context: I began using egg tempera earlier this year, so I am quite new at it. I use the detailed true gesso recipe that Koo Shadler kindly shared on a website (around 8 coats on each side of masonite panels). I use pigments from Natural Pigments and also some from my grandfather who was a painter and got them from a regular paint store back in the 1950's to 1980's (which I manipulate carefully since I don't exactly know what they contain). 

Methods of transfering drawings so far for other paintings:

-go straight on the panel in a Robert Vickrey way, and use observation skills and previous sketches... althought I would not dare to compare myself with such a great artist, it is a fun method but this time my image contains architectural details that I want to transfer from my drawing. 

- charcoal (little holes on the drawing with a needle, then trace the lines with charcoal on the paper and charcoal dust goes through the holes and remains on the panel, tracing lines). I did not find it precise enough and I wanted thiner lines. 

- draw with a regular HB pencil on wax paper. I apply a medium coat (here, I mean egg yolk + water+ pigment) on my panel. I put my wax paper ontop of it when it is dry (about 5 minutes so that the paint does not come off, but I want my paint to be quite fresh), graphite lines facing me (no graphite on the pane). I take a sharp pencil or tool and trace gently but firmly my lines again on the wax paper. Then, when I lift the wax paper, I can see subtile glossy lines on the gessoed panel (does not take the paint off or scratch the panel). However, it only seems to work on quite fresh paint.​​

My problem: The drawing that I want to transfer is quite detailed and the paint will be too dry as I trace my lines using my wax paper method. I hesitate to trace lines with graphite or using tracing paper because I am afraid the lines might show off through the paint (I sometimes like to make a few changes through my creative process or some other times, I use light colors). However, I might be totally wrong.

Thanks a lot for indicating me what would be the best way to transfer my image.

Best regards,

Aude (sorry for the mistakes, I am French from Québec)

Best practice with flexible surface

Question asked 2021-10-04 10:06:41 ... Most recent comment 2021-10-04 12:55:12


The resource guide mentions affixing a backing board to a stretched canvas. How might this be accomplished? If the reason for using a stretched canvas rather than a panel or canvas mounted to a panel, is that the stretched canvas is large and weight is an issue, will the backing panel add weight? Can it be done in pieces as wood that large is not readily available? Does the guide mean to stretch the canvas around the wood and staple it? Or does it mean to glue panels to the back of the canvas?

Non-Rigid Surface oil painting

Question asked 2021-10-04 06:52:55 ... Most recent comment 2021-10-04 12:50:32
Oil Paint
Hello all!

I know it is best practice for oil paintings to be made on a rigid substrate, to reduce the cracking you get with a flexible surface that also reacts to humidity and temperature changes over time. This would include painting on a wood panel, hardboard, aluminium and paperboard, with a well sized and primed surface, with or without a layer of canvas on the top or muslin embedded in a genuine gesso ground.

But, is there anything that can be done to help make a more permanent painting when a rigid substrate cannot be used, as with large paintings where a lightweight surface is required? What is best practice for oil painting on a stretched canvas?

Thank you for any help.

oil paint layers adhesion

Question asked 2021-09-27 19:17:30 ... Most recent comment 2021-09-27 21:39:55
Oil Paint

If an oil painting takes years to complete how does an artist get each layer to stick to the next? You hear a lot about fat-over-lean for working in layers but I haven’t heard much about beading up and adhesion problems with working in layers, I have had to work hard to find information.

I have been building up layers of oil paint on canvas and sometimes find that the paint beads up on the previous layer, especially if I make the new layer oily. If I make it less oily and physically brush it around alot I can usually get it to finally lay on smoothly but I am finding some canvases have poor adhesion and after the layer has dried for a few weeks I can easily scrape parts of the new layer of paint off with my fingernail to expose the layer underneath. But not everywhere, just in some areas. This occurs somewhat with a lower surface layer that has dried for one week but more so with a lower surface layer that has dried for a year.

I haven’t kept track of which oil painting mediums that I used have caused the most problems. I do rinse and dry the surface to remove dust. I don’t want to sand the surface because it seems destructive and would remove part of the painting that I did intend to be there.

So I have quite a few questions about adhesion, if any of you could help me please.

Am I gently scratching too soon, will I find if I wait 6 months that the surface will be harder?

How durable should a dried oil surface be, should I be able to scrape it with a palette knife and it is fine?

Aren’t I supposed to be using fatter paint for upper layers?

What causes the closed off surface? 

What is the polarity I have heard mentioned?

I understand that there needs to be a mechanical bond and a chemical bond but I don’t quite know how that is failing in this case. If I etch the surface will I get a mechanichal bond, but if the surface has oxidised is it too late to get a chemical bond?

I read that you can paint a layer of medium or solvent over the surface to reactivate it, but it hasn’t worked for me. Oil of spike is the strongest solvent I know and it removes well-dried colour but doesn’t seem to ‘etch’ the surface.

I have used a method of applying onion juice to lightly etch the surface and I can see that it changes the surface so that water no longer beads up on the surface and it stops the beading of oil paint and the poor adhesion. Is there anything unsound in this technique? I wash the onion off with water.

I’ve read that using safflower oil makes the poor adhesion of layers worse, is that true?

Are some pigments worse?

Is this surface fragility the same as ‘delamination’?

Thank you for any help!


acrylic over very dried oil

Question asked 2021-09-27 19:04:41 ... Most recent comment 2021-09-27 20:32:50
Oil Paint Grounds / Priming

​I wanted to check something with the experts. I was told a few years ago that an artist was told by a restorer that on very old oil paintings they use acrylic for the repairs. I assume this was done to be a visible repair so as not to pretend to be the original painting. But the artist I was talking to, interpreted this to mean that if the oil is fully dried then you can use acrylic over it.

I wanted to check if a fully dry (2 years or more) oil painting will accept acrylic and create a stable painting. And that leads to someone asking me about putting acrylic primer over an oil painting. She said she thinks it is not a good idea but that all her artist friends assure her it is what they all do to reuse a surface.

Would it make any difference to use the acrylic over a varnish, would it be better or worse?

wet brushes and oil painting

Question asked 2021-09-27 18:26:27 ... Most recent comment 2021-09-27 20:28:30
Oil Paint

​I sometimes wash my brushes, squeeze out the water and continue oil painting. The damp brushes do not interfere with the painting process. But I wondered if a small amount of water would cause problems with longevity later. Does anyone know?

Cadmium Orange

Question asked 2021-09-24 17:24:00 ... Most recent comment 2021-09-25 21:38:22
Pigments Oil Paint

​A very newbie question:  A fellow oil painter asked me if cadmium orange pigment would be brighter than a mix of cadmium yellow and a cadmium bright red.  Bright enough for me perhaps.  It would be rare that I don't tone down the brighter colours, but they want the very brightest orange.   I keep flipping on the absolute certainty of the answer.  It's made from the same stuff.  What I mix looks bright, but then, it will be made from little bits of red and yellow, not little bits of orange.   


Animal Glue & Bloom Strengthr

Question asked 2021-09-19 08:44:55 ... Most recent comment 2021-09-22 05:40:32
Animal Glue

Hello All,

A few questions about animal glues. My understanding is that unless specified as genuine rabbit skin, most animal glues are a mix of animal sources (mostly cow, some pig) and the term "rabbit skin", rather than denoting origin, indicates a quality of glue: high bloom strength and 100% collagen.  My idea of high bloom strength is 450 or so - but I see companies selling so-called "rabbit skin" glues with lower, 350 bloom strengths.  So...

1. Are there industry standards outlining what qualifies as a high enough bloom strength to denote a glue as so-called "rabbit skin"?  

2. If not, what is generally accepted as a high bloom strength?

3. If a glue isn't 100% collagen, what else is it (aside from collagen)?

Thanks if you can offer any insight on these questions! 

Koo Schadler


Question asked 2021-09-19 09:04:00 ... Most recent comment 2021-09-22 05:33:41
Egg Tempera Paint Additives Studio Tools and Tips Pigments

Hello again (second question in one day)...

I want to better understand preservatives used in pigment pastes (helpful in mold prone colors) and egg yolk medium (not something I recommend, as I prefer a fresh egg, but many painters want/need to make medium last longer).

1. Are there benefits to using Phenol (carbolic acid) over alcohol (95% or higher purity) as a preservative?  Alcohol is less noxious than Phenol (I believe, tho' not sure), more readily accessible, and has the added benefit of being a dispersant.  So is there a reason to prefer Phenol to alcohol as a preservative?

2. Phenol and alcohol are volatile.  I would presume that once they evaporate off, they haven't imparted a lasting, preservative benefit to a pigment paste or yolk medium, yes?  Are their preserving qualities present only when the phenol/alcohol itself is present?

3.  Is the moisture within a pigment paste or medium enough to keep phenol/alcohol from volatilizing, or will they volatilize regardless (i.e. even a hydrated pigment paste will lose the phenol/alcohol content over time; hence more preservative must be added for ongoing protection from mold in a paste)?

4.  Given the above, what do you think of the benefit of non-volatilizing preservatives (such as clove oil), if added in very small amounts?  Or is the non-drying nature of this preservative more problematic than its benefit of staying present and thus continually preserving?

A bit in the weeds here, but curious tempera painters want to know...  

Thanks, Koo

House paint as a primer for canvas painting

Question asked 2021-09-19 13:00:03 ... Most recent comment 2021-09-21 22:06:26
Grounds / Priming

I know many artists that use house paint (latex emulsion paint) as a primer for canvas, because they think that the cheaper house paint will work the same as artist acrylic dispersion primer. I point out that house paint is always sloughing off as part of its characteristic of being easily cleaned, that it is designed to last for only 10 years and that a wall is not a flexible surface like a stretched canvas and that the paint in my flat is cracked all over because house paint isn’t flexible. So for those three reasons it is not the same. 

Though I have noticed a big difference in sloughing off between types of paint  - the cheap DIY paint in large buckets that is used in galleries wipes off white on a sponge, which is excellent for removing a stain by removing a layer of paint, but the paint in my bathroom is designed for water and does not scrub off on a sponge when wetted. And I wonder if tougher exterior paint is better.

Some people learned from art school tutors to mix PVA into household emulsion to make a primer. Others use a very good, one coat, stain killer household paint that says it promotes adhesion.

Everyone who uses household paint to prime canvases gets quite defensive and starts saying PVA is PVA, that house paint is the same as acrylic dispersion primer and that artist acrylic dispersion gesso is a rip-off. They say that the wall paint in their house lasts much longer than 10 years and they only re-paint for decorative reasons. 

None of this is about the usage of house paint for aesthetic or conceptual reasons - they all use it for economy. 

Is it correct to say that household latex emulsion paint is not the same as or equivalent to acrylic dispersion primer and that it isn’t a good foundation for permanent paintings? If that's true, can anyone give a clearer picture of how it is different and what problems might arise from using it?

how does solvent affect PVC if it evaporates?

Question asked 2021-09-19 14:03:55 ... Most recent comment 2021-09-20 10:34:05
Oil Paint

I have a fat over lean question.

Does solvent act as a minus of fat (or PVC)? It seems like it does when it is added neat, it thins the paint so it is less fat, spreads it farther on the surface. But it must only temporarily reduce the PVC because as soon as it has evaporated then the ratio is the same as before, right? And when solvent is part of a medium (solvent and oil) then it seems like only the amount of oil matters since the solvent evaporates, you are just adding up the overall oil content of each layer.

Can anyone clarify this?

solvent fat-over-lean question

Question asked 2021-09-20 06:48:48 ... Most recent comment 2021-09-20 10:31:00
Oil Paint

Does solvent act as a minus of fat (or PVC), even though it evaporates? It seems like it does when it is added neat, it thins the paint so it is less fat or concentrated, spreads it farther on the surface. But it only temporarily reduces the PVC because as soon as it has evaporated then the ratio is the same as before, right? And when solvent is part of a medium (solvent and oil) then it seems like only the amount of oil matters since the solvent evaporates, you are just adding up the overall oil content of each layer.

Can anyone clarify this?

Alcohol inks

Question asked 2021-09-07 14:10:47 ... Most recent comment 2021-09-12 19:23:01
Egg Tempera

​hello egg tempera experts! 

I recently bought a pack of waterproof alcohol inks by Jacquard.  

Do you think these are ok to use under an egg tempera painting? As an underpainting? I thought I would experiment with different color ink underpaintings, but I don't want to find out it was a bad idea when it's too late.


Correct way to size fabric with Rabbit Skin Glue?

Question asked 2021-09-04 09:02:20 ... Most recent comment 2021-09-09 13:48:29
Sizes and Adhesives

I can't find a definitive answer for how much RSG is too much or too little. I have been using it while in liquid form, before it cools, and applying with a sponge until it soaks through the back. A friend says that's too much. I do get spots where the fabric is slick and shiny.

I thought to do a light coat on front and light coat on back, but that seems to be not recommended. Is there a better way to do this and still make sure all fibers are saturated? 

Standoil film breaks to aglomerattes

Question asked 2021-09-02 14:54:12 ... Most recent comment 2021-09-08 15:32:55
Drying Oils Oil Paint Paint Mediums

​Dear all,

I painted in multiple oil glazes, first linseed oil and pigment followed by last two or three layers of stand oil and pigment. ​

Stand oil is linseed heated without oxigene and I mix binder and dry pigments prior to painting

The problem happens when I aplly second or third layer of stand oil and pigment, the paint film once brushed equally in few minutes breaks down to aglomerate. It looks like one spills water on horizontal flat surface and then water shrinks to unregular pattern of small shapes. 

It happened when I add solvent and without it.

Why this happens and what could I do to avoid it?

Kind Regards,

Damir P.

Graphene Veils

Question asked 2021-08-27 09:16:48 ... Most recent comment 2021-09-08 08:46:29
Art Conservation Topics

Just wanted to post this as although it's just at the stage of research it's interesting. It's using a thin layer of Graphene to protect artwork from degradation:

Any Specific Gesso Recipes from 16th Century Italy?

Question asked 2021-07-30 20:53:48 ... Most recent comment 2021-08-09 14:05:18


Can someone provide specific gesso recipes used in 16th-century Italy and/or provide resources that might expound upon such recipes? Thank you.

Making changes to a dried oil painting

Question asked 2021-07-30 02:22:02 ... Most recent comment 2021-07-31 22:41:07
Oil Paint

​Hi All,

Periodically I need to make some changes to an already dried oil painting. Usually the painting is only a few weeks old, but sometimes a few months. To date I have either scraped the offending bits off (but this can leave a trough); sanded it off (not sure if this is good for the overall painting) or painted over it with thicker paint (only works where the overlayer is compatible with the rest of the terms of thickness, opacity, etc.).

Would really like to know if there is a better way and, also, what do you think of my 3 methods above?

Thanks in advance,

PS: I usually paint on gessoed canvas panels, although I sometimes use stretched canvases. In the latter case I would usually hold some firm material behind the canvas so that any scraping/sanding did not stretch the canvas in the local area (unfortunatery this dosen't always work and I end up with a localized backwards depression in the canvas).


Paraloid B72

Question asked 2020-10-19 15:44:39 ... Most recent comment 2021-07-30 09:54:23
Egg Tempera


I am planning to use Paraloid B72 on Egg tempera and i have some questions since it will be the first time i will be using it. I am planning to use it on icons painted with fairly high egg yolk content.

1. What percentage should be used for preparing B72 for this kind of paintings?

2. I have read that there are multiple solvents that can be used. Does the polarity of the solvent affect the paintings?. Someone mentioned that non polar solvents have a tendency to cause Fatty acid migration/ foggy spots on paintings. This was mentioned for varnishes that sink into the paintings. How does this apply to the isolation layer produced by B72. I am between using acetone or ethanol.

3. What will be the effects of sealing the paintings if they haven't cured for over a period of 3 months? For example a period between one to two weeks..

Thank you

Testing our Notification System

Question asked 2021-07-14 14:26:49 ... Most recent comment 2021-07-16 14:20:35

Please ignore, i'm tesing our notification sytem


PVA for sizing

Question asked 2021-03-02 13:58:27 ... Most recent comment 2021-07-13 22:06:03
Sizes and Adhesives

Hello all,

I have a question about PVA for linen sizing:

My understanding is that the linen industry has mostly stepped away from using RSG due to its hygroscopic nature and has moved towards PVA for its durability and longevity.  However, I just read that Winsor and Newton advises against PVA for sizing because it will “disintegrate prematurely leaving the remaining painting with no foundations”. Is there research to back up or refute this claim? 

Thank you for any insights you may have.



Rabbit Skin Glue change

Question asked 2021-07-12 08:51:35 ... Most recent comment 2021-07-12 16:21:06
Oil Paint Sizes and Adhesives

I know lots of oil painters who paint directly on RSG size on linen, with no primer. A frien recently encountered a problem I wanted to ask about.

She prepared many canvasesin her normal way (I do not know the strength of her RSG or how many coats). She used all but one of the canvases. She went back to paint onthe last canvas after one year and found that the oil paint penetrated the size. 

We talked it over and since nothing but the curing time was different we figured that the year of drying had shrunk the size away from the fibres so the seal was no longer complete or even. Does this sound right? It would mean that the layer of oil paint helps stabilise the RSG, perhps sealing it on the one side so there was less surface to react with the humidity in the air. Or does anyone see another possible explanation?

Thank you.

Rabbit Skin Glue change

Question asked 2021-07-12 08:50:53 ... Most recent comment 2021-07-12 08:43:00
Oil Paint Sizes and Adhesives

I know lots of oil painters who paint directly on RSG size on linen, with no primer. A frien recently encountered a problem I wanted to ask about.

She prepared many canvasesin her normal way (I do not know the strength of her RSG or how many coats). She used all but one of the canvases. She went back to paint onthe last canvas after one year and found that the oil paint penetrated the size. 

We talked it over and since nothing but the curing time was different we figured that the year of drying had shrunk the size away from the fibres so the seal was no longer complete or even. Does this sound right? It would mean that the layer of oil paint helps stabilise the RSG, perhps sealing it on the one side so there was less surface to react with the humidity in the air. Or does anyone see another possible explanation?

Thank you.

I spoke too soon. The forum will be back to normal in a few days.

Question asked 2021-06-30 10:52:04 ... Most recent comment 2021-06-30 10:51:00

​I spoke too soon. The forum will be back to normal in a few days.

Egg Tempera - isolator/varnish using Lascaux UV Protect Spray

Question asked 2021-06-23 05:39:50 ... Most recent comment 2021-06-30 10:49:58
Egg Tempera Varnishes Matting, Framing, and Glazing

​How quickly can one apply a spray isolator/varnish such as Lascaux UV Protect spray over an egg tempera painting?  See: One specialist art supplier in the UK suggested it could be applied as soon as the ET surface was dry as it mainly evaporated on contact.  I have made some test panels and find it works well as an isolator or finishing varnish, even after a few days when the paint is relatively fresh, but touch dry.  I have seen some previous forum entries suggesting a longer curing time is recommended (6 months or longer) but provided there are no immediate visible problems (such as uneven sinking in - which I haven't found an issue, even after isolating after a few days) are there other potential problems that could arise later on?  Of all the various preparations/combinations I have experimented with, Lascaux is the one preparation which is nicely matt​/does not sink in.  I have tried A82/Regalrez/Golden products in various ways and they are either too uneven or have an unsatisfactory high gloss/slightly plastic appearance.  I don't always have the time to wait 3-6 months which probably explains why insufficient curing is probably the cause of my issues with uneven sinking in etc - and which is why I favour Lascaux.​

On another note, if I decide alternatively to place an ET painting behind glass, which has been my practice so far, when is the earliest I can safely do so - obviously the framer will take precautions by insterting slip/beading between painting & glass.  Is it OK to fully seal the back or can one allow breathability & air circulation ​by not taping up..?  

Thank you for any advice. Zarina

Recent problems with MITRA

Question asked 2021-06-26 23:21:23 ... Most recent comment 2021-06-26 23:20:00

​Hi all. UD was doing routine server work and it caused some glitches in a number of associated webpages. I would have warned everyone, but I learned after the fact and the site was not working, making it impossible for me to post about the problem. We now appear to be out of the water on this. I look forward to continuing our dialog about art and materials and techniques.

Egg Tempera on Parchment

Question asked 2021-05-24 09:37:25 ... Most recent comment 2021-06-18 14:56:47
Animal Glue Art Conservation Topics Egg Tempera Flexible Supports Gouache Rigid Supports

I once painted an illuminated image on vellum, mostly in ink and gouache, but with a small area in egg tempera.  Within a season the skin had warped, the tempera section had cracked and, in parts, delaminated (image attached, in raking light). KS ET on Vellum.jpeg  The pigment involved in the delaminated area – genuine lapis lazuli – no doubt (due to large particle size and rigidity) exacerbated the inherent problem of an inflexible medium on top of a hygroscopic, moving support.  

1.  Medieval manuscripts are often said to be painted in "tempera".  How many are actually "egg tempera" versus simply a water-based "tempera paint" (gouache)?  Is the same, somewhat confusing terminology that is seen in early Egyptian art (i.e. many images labeld "tempera" are not egg tempera) applied to manuscript illumination? 

2. If manuscript illuminations are, in fact, egg tempera, how have them been preserved?  Were they thinnly painted?  Is the binding of a manuscript enough to keep them stable? Or, in fact, have egg tempera illuminations suffered more than images done in goauche or watercolor?

3. Any thoughts on adhering animal skins to rigid substrates?  The facts of egg tempera (a high PVC paint that gets more brittle with age) combined with practical experience tells me animal skin supports and tempera are a problematic combination. Given how water-loving and strong animal skins are, would adhering them to a rigid support resolve the problem? Or exacerbate it (since skins and wood expand/contract at different rates = lots of stress in the artwork)?  If not on a wood support, how about vellum on other substrates (paperboard, ACM, plastic)?

Any thoughts on the above are most welcome!  Thanks, Koo Schadler

Tubed Tempera, Mysterious Craquelure, Venus

Question asked 2021-06-18 14:54:06 ... Most recent comment 2021-06-18 14:26:00
Egg Tempera

1.   Zecchi's tubed egg tempera paints are made from pigment, freeze-dried egg yolk, gum arabic, and preservative.   

- Any thoughts on freeze-dried yolk as a binder? 

- What would be the reason to combine yolk and gum Arabic binders in a single paint?

2.  Mysterious Craquelure.  Tempera painters occasionally report a mysterious ‘craquelure’ that appears in the uppermost layers of tempera paint during the painting process.  It starts out as barely visible lines that gradually increase with successive layers; as more paint is applied, lines coalesce into a network of minute cracks, and can eventually cause paint to flake and delaminate.  It’s seemingly associated with well-developed areas (lots of underlying layers), and generally involves titanium white.  I don’t know what causes this, I can only offer tentative explanation, among them:

 a. Underbound, very diluted paint.  When too much water is added, at some point the various components become so separate, binder so attenuated that the resulting paint film is friable and under bound.

 b. Over saturating underlying paint layers with water. Studies of solvents applied to ET indicate that spirit-based solvents  leach lipids; water seems to induce swelling in the paint film.  If a curing film is compelled to repeatedly expand and shrink, the stress could weaken bonds being formed in the polymerization process, and result in cracks.  

There is also the speculation that, in an over saturated surface, excess moisture might draw yolk binder downward so that upper layers become under bound and fragile.  This latter theory doesn't seem as likely to me, but could it be possible?

c. Poorly dispersed titanium. TW’s fine particle size tends to clump together, and needs to be carefully and thoroughly dispersed - yet I often see students give it cursory attention with the palette knife.  So, perhaps aggregate clumps of poorly dispersed titanium contribute to cracking? 

I favor explanation ‘b’- because of the circumstances and solution to the mysterious craquelure I experienced a few times in my early painting days. It generally occurred when I worked very rapidly, quickly piled up layers, and thus also accumulated lots of water within the paint film down to the gesso.  To fix the problem, whenever I build many layers in a short amount of time, I continually and thoroughly dry underlying layers.   Since adopting these work habits, I haven’t experienced “mysterious craquelure”. 

Any thoughts would be appreciated!

Damage to traditional gesso surface

Question asked 2020-06-25 11:16:14 ... Most recent comment 2021-06-17 23:24:01
Rigid Supports Art Conservation Topics Egg Tempera Grounds / Priming

Hi! I have damage to the surfaces of some traditional gesso panels I made: traditional gesso on muslin on Baltic birch ply. The surfaces have been damaged. In some cases the muslin fabric below the gesso has been exposed. In other cases, I hesitate to sand away scratches in case of exposing more fabric. My understanding is that gesso layers should be applied while just dry to the touch, and not after the layers have cured, as is the case with my panels. Any advice on the possibility of repair would be much appreciated. They will be used for egg tempera, so surface aberrations are unfortunate given the thin nature of tempera. Thank you!

Tubed Egg Tempera, Freezing Egg Yolk

Question asked 2021-06-17 16:23:02 ... Most recent comment 2021-06-17 16:15:00
Egg Tempera

I'm trying to better understand a commercially produced, tubed egg tempera paint made from pigment, freeze-dried egg yolk, gum arabic, and preservative.  Freezing egg yolks (as discussed on various cooking forums) seems to be acceptable if there are additives (sugar, salt); otherwise freezing seems to break the yolk's natural emulsion.  Any thoughts on freeze-dried yolk as a binder?   Thanks, Koo 

I am back

Question asked 2021-06-04 14:30:45 ... Most recent comment 2021-06-04 14:30:00

​Thank you other moderators for filling in for my in the last two weeks.

Multimedia Artboard

Question asked 2021-06-01 08:29:25 ... Most recent comment 2021-06-04 08:48:53
Rigid Supports Oil Paint Art Conservation Topics

​They claim this material is archival. Is it?

ABS plastic panel

Question asked 2021-06-01 08:32:33 ... Most recent comment 2021-06-03 16:48:06
Art Conservation Topics Oil Paint Rigid Supports

​Is this a suitable archival support for permanent art?

Fire retardant over acrylic and acrylic spray paint

Question asked 2021-06-02 16:18:58 ... Most recent comment 2021-06-02 18:29:02
Acrylic Health and Safety

I have been asked to cover some finished paintings with fire retardant. The paintings are acrylic and acrylic spray paint on maple plywood. Is this going to ruin the paintings?

Signing an oil painting

Question asked 2021-05-31 15:41:24 ... Most recent comment 2021-06-01 20:33:03
Oil Paint Studio Tools and Tips Pen

​Need suggestions for a commercial quill or penlike vehicle to hold medium viscosity oil for signing oil paiantings OR

Is there an italic Sharpie like product whith which it is OK to sign an oil paiinting? Small brushes too broad, too many bristles.

Water Gilding

Question asked 2021-05-28 07:05:20 ... Most recent comment 2021-05-30 07:43:53

​Hello everyone,

I was wondering if there are any recipies for making my own Gilders clay bole from scratch? 

I read the post about the 19th century gilders clay bole,but information is missing..

Thank you

I will be away from MITRA until the 1st. Brian Baade

Question asked 2021-05-25 18:41:11 ... Most recent comment 2021-05-25 18:38:00

​Hi all

I have been hard at work preparing my initial documents for tenure. This is the reason that I have not responded much the past week. I am going to focus solely on this until the 1st of JUne. I see that the rest of the moderators, especially Matthew,  have been doing a great job and I look forward to returning to posting on a regular basis.

Oil Sticks - does the wax cause problems?

Question asked 2021-05-24 13:11:09 ... Most recent comment 2021-05-25 15:15:59
Oil Paint

​I am presently creating oil paintings using oil sticks and oil paints. I create my first layer using Shiva Oil Sticks, which have a matte finish and dry to the touch in less than 24 hours.  My second layer consists of Sennelier Oil Sticks, which are much oilier than the Shivas.  My final layer is completed using Gamblin Oil paints applied neat.

I've read elsewhere that oil sticks are not as compatible with regular oil paints and do not dry as well as or create as strong a film as regular oil paints, which can lead to problems down the road.  

What are your thoughts on this?  Thank you!

Tempered Hardboard - painting directly on it with oils

Question asked 2021-05-15 01:54:18 ... Most recent comment 2021-05-25 10:10:57
Rigid Supports Grounds / Priming Oil Paint

​Hi.  I'm a bit confused about tempered hardboard and whether it's considered to be an archival support for oils.  Can I paint directly on it without any prep at all, including skipping adding any oil ground?

I posed this question to one of the popular oil paint companies and was told that I could paint directly on the hardboard because there's little risk of the board absorbing either moisture from the atmosphere or oil from the paint, so there's little risk of warping or movement from moisture, or degradation from the oils.

One of the popular acrylic paint companies suggests 2 coats of gloss medium followed by acrylic gesso.  I know there's debate over whether painting oils over acrylic sizing and ground is archival.

What are your thoughts of these issues and do you recommend painting oils directly on tempered hardboard with no sizing or ground at all?

Thank you.

Egg Tempera Varnish Clarifications

Question asked 2021-05-15 10:25:59 ... Most recent comment 2021-05-23 07:35:58
Egg Tempera Varnishes


I am updating the section in my egg tempera book on varnishing.  It's a very complicated chapter, unfortuantely, because it's an unfamiliar subject to many tempera artists, so there's a lot to explain; and there's the added complication of so many potential products (both as isolators and final varnishes).  Of course I can't cover every product, I discuss what's most recommended and ones I'm familiar with - still, it's a challenge to organize and make coherent.

Given the above, I'm trying to get the right nomenclature to distinguish between water-based synthetic polymers (primarily various Golden products, although I also include water-based PVAs offered by Gamblin and Talas) and solvent-based synthetic polymer resins (B72, Mowilith 20, Soluvar, MSA, Laropal, Regalrez).  So my questions are..

- Are both water-based and solvent-based synthetic polymers considered resins, or is the term "resin" associated only with solvent-based coatings?  Is there a reason to distinguish solvent-based synthetic polymers as "resins" (does it contribute anything to understanding that group of coatings)?

- B72, Soluvar and MSA are HMW, yes?

- B72 is soluble in acetone, toluene and xylene; Soluvar and MSA soluble only in true mineral spirits, yes?

- Laropal and Regalrez are LMW, yes? 

- Both Laropal and Regalrex are soluble in either true mineral spirits or OMS?

- Is it important to include the numbers in Laropal A81 and Regalrez 1094?  I'm sure they're meaningful, but it's already confusing for newcomers to absorb these strange (to them) chemical terms, and lengthening their names with meaningless (to a newcomer) numbers can make eyes glaze over... 

I know MITRA has an excellent section on varnishes - I'm including the link in my book.


Koo Schadler 

Student Grade paint

Question asked 2021-05-15 05:14:57 ... Most recent comment 2021-05-23 03:06:09
Acrylic Art Conservation Topics Oil Paint Scientific Analysis Technical Art History

I have the perception (whether right or wrong) that Student Grade oil paint from the main manufacturers contains an abundance of fillers and that these make cause long term problems with the paint film (aluminium stearates, etc..) compared to the use of Artist Grade oil paint.

I also have the perception that Student Grade acrylic paint (from a good manufacturer) does not have the same issues as the acrylic paint film is much more stable over time.

Am I wrong in these beliefs?


oil painting on stone veneer

Question asked 2021-05-18 14:51:13 ... Most recent comment 2021-05-19 17:03:53
Industrial and Non-Traditional Products Sizes and Adhesives

I have found a stone veneer product that I would like to paint in oils on.  It is very thin and has a backing that consists of an adhesive  ( that has a PH of 3.5- 4) and cotton.  The company has said to me that the PH needs to be this in order for the product to be waterproof. .  So my question (s) is this:  Is this a bad idea and if so, can it be fixed?  ( Example, could I use buffermount to adhere the backing to an archival board say?  Could I paint some type of ground on the stone's surface to  seal it/ give it more protection?   I really want to work on this because it is super lightweight, pliable and I have lots of ideas.

silicone paper

Question asked 2021-04-29 10:26:15 ... Most recent comment 2021-05-19 09:48:41
Industrial and Non-Traditional Products Handling and Transportation Art Conservation Topics Storage

​I have another question for you experts:

I am looking for silicone paper, for wrapping art. But it's hard to come by, and expensive. Unless you could use silicone paper used for the food industry. Then it suddenly is very affordable and relatively easy to get.

Do you people know if it's the same product? Is it safe to use foodgrade silicone paper for art?

Wax Mediums

Question asked 2021-05-15 18:49:47 ... Most recent comment 2021-05-16 07:18:23
Encaustic Varnishes

​A few questions about wax mediums.

1. Most wax mediums have some sort of resin and solvent.  Does anyone know if Renaissance Wax contains a resin (its ingredients are listed as microcrystalline waxes & mineral spirits)?  If not, what causes it to harden; is it just the inherent hardness of the mix of petroleum based waxes in it, once the solvent content has evaporated?

2. Dorland's Wax Medium is made from beeswax, paraffin, microcrystalline wax, dammar; it does not list its solvent content in the ingredient list, just says "can be thinned with turpentine or mineral spirits".  Yet other places on the web say it can be thinned with OMS.  Anyone know it's solvent content?

3. Are microcrystalline waxes (no color, harder) preferrable to bees wax, or are they equally good?

4. Can solvent-based wax mediums be applied on top of water-based synthetic polymer isolators (such as a PVA, GAC 500, etc)?

5. I presume that for a wax medium to go on top of a solvent-based isolator, it must contain a different solvent from whatever went into the isolating coat; otherwise applying the wax medium would dissovle the underlying isolator - yes?

6. Has anyone tried the Williamsburg wax medium, which is solvent free, as a finishing layer?  If so, any thoughts on its appearance, drying time, etc.?

7. Finally, if George O'Hanlon at Natural Pigmetns could clarify the practical differences between his two wax mediums (Rublev Wax Medium [beeswax, dammar, odorless mineral spirits - Rublesol, I presume?] and Conservar Wax Medium [microcrystalline wax, aldehyde resin, mineral spirits], that would be most helpful.

Thanks! Koo Schadler

Oil Paint on Convex and Concave Solid 22kt Gold

Question asked 2021-05-01 10:14:21 ... Most recent comment 2021-05-15 05:20:45
Rigid Supports Gilding Oil Paint Grounds / Priming

Hi, I'd really appreciate some advice on an unusual query; I've been referred to this amazing website through the Painting Best Practices Group on Facebook. I've had a good look through the resources and forum threads on here, but I still have some questions:

I’ve been asked by a jewellery designer if I could paint miniatures in oil paint onto slightly concave 22ct gold ovals, circa 1mm thick, to be set into a bracelet. I’m wondering what a concave surface will do to the paint layers over time.

I’ve previously painted on convex gold domes for the same client, treating it like painting on copper/on top of gold leaf (there was limited testing I could do on solid 22ct gold!): the gold was completely obscured, as it was purely to make sure the whole jewellery piece was made of precious materials. I very lightly abraded the gold, degreased it with denatured alcohol, then two thin coats of a flexible primer: Liquitex clear gesso primer (chosen because it was difficult to scrape off copper that had been prepared in the same way. It was also quite difficult to remove from the gold dome two months down the line, i.e didn't peel, when I removed the finished painting to make way for a new design). I then painted in very thin layers using the minimum amount of medium: progressively fatter turps and linseed oil. The final paint thickness is very thin. 6 months on, the convex domes appear unchanged (if 6 months is a reasonable cure time? I’m expecting the cure time to be slow because of the circa 1mm thick metal support, but it is very thinly painted).

For the concave domes, I’d be using the same process and medium.

- Is a concave surface inherently unsafe for indirect oil painting?

- If not, would an alkyd primer, or a lead-based primer be a better product than the acrylic gesso primer? I'm working on the assumption that the gold is largely chemically inert, with circa 2% copper and circa 6% silver - I gather lead primers bind chemically to copper, but my only option (as I'm in the UK and lead products have been phased out) is an old tube of Daler Georgian Flake White – it doesn’t say if it contains zinc, or if it’s linseed oil. I don’t know if this would be up to snuff as a priming layer at all.

Thank you for reading this long-winded post!

Muller vs. Mortar/Pestle

Question asked 2021-05-12 07:55:59 ... Most recent comment 2021-05-14 06:44:26
Pigments Studio Tools and Tips

Most pigments come ground to optimal size, but occasionally an historic or earth pigment (anything larger than about 40 microns) benefits from a bit of grinding.  A glass muller (about 5.5 Mohs - yes?) isn't necessarily hard enough for grinding (depending, of course, on the hardness of the pigment being ground), nor does a muller's shape direct force in such a way as to grind effectively (rather, its flat bottom shape seems best suited to dispersing pigments).  So a mortar and pestle seems a much better tool for grinding (and the harder the material it's made from, the better; i.e. agate, porcelain).  Yet I see mullers often discussed or even recommended for grinding pigments.  

Is a muller suitable for grinding (I think of mullers as primarily suited for dispersing)?  Is a mortar/pestle unquestionably preferable?  Is any substance added to the base of muller to increase its hardness?  Any other thoughts?  Thanks.

Pva on raw unprimed linen problem

Question asked 2017-11-25 11:39:09 ... Most recent comment 2021-05-12 10:34:32
Sizes and Adhesives

​Hi! Im an art student at the National academy of fine art Oslo, Norway.   

I'm interested in using raw linen canvas in my painting, I've previously bought white  grounded linen and stretchid it the unprimed back as the front. Recently, I received unprimed linen from artist store.

I have experience with rabbit skin glue but since i want to use oilpaint directly on the "size" this is not on option?. I started using artist grade PVA, and a professor tought me how to dilute it with water, ca 1/5 pva to water. it worked well with two coats on cotton but when i started priming the linen the result was really horrible.

i stretched the raw canvas nicely and tight on a stretcherframe and started brushing on pva/water.  while wet the linen got really firm and tight but after drying overnight the canvas was completely slacking.  after yet another coat the canvas was tight (wet) and later turned slacking but hard as the pva dried.  i made tests where i put on the pva undiluted and the result was good but the pva layer dried almost instant, it was uneven and slighly milky plastic looking.  

I also started pva priming the canvas unstretched and later had to really struggle to force the canvas to get tight on the frame with canvas pliers, as it did not get really stretched i made the huge mistake to brush some water on the canvas, it get really bad after drying, untight and full of ripples. i have made alot of searching for answers, my proffessors just told me that the key is to dilute with water, and restretch the canvas and give it more glue coats. wich i did, and every time the same thing, tight when wet and loose dry.     

after i while i found this article,  its the same problem i encountered with pictures  

i read that professional canvas maker like cleassens of belgium use acrylic glue to their canvases and coating both sides, is this a better option?   can you dilute pva with something other than water?

I know about the Golden products but now i ended up with having alot of PVA and trying to make it work.     



Oil strikethrough on linen

Question asked 2021-05-11 08:33:39 ... Most recent comment 2021-05-12 08:00:33
Grounds / Priming Drying Oils Animal Glue Flexible Supports Oil Paint Sizes and Adhesives


I commonly paint on a good quality, heavy cotton duck (on stretchers) which I paint on unprimed. I size the canvas with three coatings of fairly dilute rabbit skin glue (1:20 ratio) and paint straight on top. I have been doing this for several years, and my usual test of whether the size is sufficient to protect the cotton from the linseed oil in the paint is to check for strikethrough on the back of the canvas - usually my sizing method prevents any strikethrough, and seems successful. I'm also careful not to create a thick 'layer' of rabbit skin glue, as I'm aware that this can cause problems of delamination and animal glues in general are a bit vulnerable to the environment. I look for a very slight glittering on the surface of the cotton to judge that the size is going to be effective.

For my most recent project I decided to switch to linen. I have what I think is a good quality linen, but when I've stretched and sized it according to my normal method, I'm getting some quite bad results. There is a lot of oil strikethrough happening. I believe that the oil is actually going through the holes in the linen's weave, and then soaking into the back side, since the weave seems rather loose compared to the cotton I usually use, and I can see pinprick holes. My plan to remedy this issue (on the canvasses I haven't already started painting) is to add another layer of rabbit skin glue, at twice the usual strength, and attempt to have the glue size 'plug' the holes in the weave and therefore prevent paint getting through (so basically the usual job of a primer). Adding a layer of primer isn't an option because I already have a detailed sketch on the canvas and need my ground to be transparent so I can see it.

Is this an acceptable strategy to mitigate this problem? Is there anything I can do to my initial layers of oil paint to minimise strikethrough? Adding solvent seems to make it worse, as the resulting thinner paint finds its way through the weave even more readily. I have also been considering relaxing the tension by moving the staples, while the linen is wet with glue, in the hope that when it dries and re-tensions the weave won't be quite so 'stretched'.

I've been reading a bit about the debate over how disastrous strikethrough really is, and it seems a little ambiguous. I'm not sure if accepting the strikethrough is a better bet than experimenting with a thicker size layer? Of course I'm aware that I might end up with oil sinking later on and have to deal with that, but my main concern now is ensuring a stable foundation.

Combine sealing an ink drawing with imprimatura on gessoed panes

Question asked 2021-05-06 13:16:10 ... Most recent comment 2021-05-06 21:21:33

With my intent to paint alla prima using Liquin Original medium with oil paint on Ampersand Gessobord, are there any problems combining OMS with Liquin Original and including an oil color to seal the India ink and tone the panel?

Nonremovable Varnish for Acrylic Painting

Question asked 2021-05-04 12:02:28 ... Most recent comment 2021-05-04 19:39:38
Acrylic Varnishes

I want to use a nonremovable varnish for my acrylic paintings. I don't want the fuss of applying an isolation coat, and I am just a hobby painter, so I am not worried about any of my paintings ever needing to be conserved in the future, or having to remove the varnish. I am looking for a layer that provides UV protection, a unified sheen, a protective layer against dust, and a surface that I can clean dust off of. Because my work is textured, I want a spray application, and I don't own or want to acquire a paint gun or an airbrush, so I want a spray can. I also want a low odor and low fume product. I have read about Liquitex Spray Varnish, and I have seen an ad for Krylon Crystal Clear. Are these good products? Is Krylon ok to use on fine art? Are there any other brands you can recommend? Thank you.​

Cloudy Acrylic Varnish

Question asked 2021-04-28 08:22:43 ... Most recent comment 2021-04-29 11:34:45
Varnishes Acrylic

​I am a relatively new artist and made a rookie mistake. .

I am used gloss varnish on my acrylic paintings for the first time.  I applied two coats of Liquitex Professional Gloss Medium and Varnish and it has made it a mess.  

I suspect I did not let it dry long enough and then overworked it (rookie mistakes). It may also be that I put it on too thickly. 

Unless it is in absolutely perfect light, it has a very glared and smudged appearance.  

Any suggestions of what I can do to fix it? I am very proud of this painting; it took a long time and is a paid commission.  I am desperate to save it.

walnut alkyd and inter layer adhesion

Question asked 2021-04-26 12:39:20 ... Most recent comment 2021-04-27 13:14:25

​Should a shiny, lower paint layer need to be roughened to give it tooth before painting over it (mechanical bond), or would the chemical bond between the two layers be sufficient?

I've been adding walnut alkyd directly to my paint blobs on the palette before painting, without OMS (which is easy to overuse), and enjoy the viscosity, but the result is sometimes a shiny layer .

Thank you,


Bohus Bial 168, anyone?

Question asked 2021-04-14 09:27:56 ... Most recent comment 2021-04-22 07:57:02
Health and Safety Environment Drying Oils Paint Mediums Paint Additives Solvents and Thinners


I wonder, is there anyone here that knows Bohus Bial 168? it is supposed to be a harmless white spirit alternative. Bio degradeble, non toxic, non volatile, better working than white spirit, all natural, etc. and supposedly you could even use it as a painting medium.

To me it sounds as too good to be true, but who knows... Would be great if it realy works...

alkyds: I'm not finding actual literature on chemistry of oil primers

Question asked 2021-04-19 09:30:20 ... Most recent comment 2021-04-19 23:19:36
Grounds / Priming Drying Oils Animal Glue Oil Paint Rigid Supports

​What the title says.

I was interested in using commercial grade alkyd oil primers to prime my own canvases, 

the only thing I could find were generic warnings from artists who were not chemists to "use only art grade materials!!"

...and that's fine if that's the answer! :)  it's more the principle than the $.  if utrecht oil primer @$60/gal >> zinsser oil-based primer @$15, I just like to know specifically what makes it so.

I just need to know WHY.  because some times, there IS no difference.  a $15, 50# bag of whiting powder from the clay supply store is the same as a $15, 4# bag of "ground marble" from an overpriced paint brand.  and some times, there really is a seriousdifference after all, and, I want to educate myself.

but just using google I'm finding very little.  and paint brands like to keep their formulas proprietary, as well.

what's the difference between a urethane alkyd and a silicone alkyd?
...and "alkali-refined linseed oil"?

are all three alkyd categories cross-compatible (will stick to each other)?
 is there a chemical relationship between a urethane alkyd and a polyurethane varnish?

alkyds are 100% compatible with traditional oil paints, or no?

enamel gets used like a marketing term all over the place for all kinds of totally different products... does it have a specific technical meaning?

"titanium white oil paint" versus "oil primer" vs an oil-based gesso (I guess acrylic gesso is more common)
 is the difference between paint, primer, and gesso, the amount of whiting powder and pigment filler versus the amount of binder?  primers have more filler to be thicker and more opaque, is it just that simple or there's more to it?

I'm sorry there's so many questions.  these are things I've wondered for YEARS and never found clear answers to. 

I even have the artists' pigments books which are fascinating.  i loved making the pigment connections when I got into both car autobody+paint and pottery glazes.
the fellow at NAPA auto paint was explaining that toyota's gold paint from 2000 bleaches in hawaii's equatorial sun to a silver-- it has quinacridone red, which is a mostly permanent organic pigment but apparently 20 yrs of direct UV exposure, will break it down).

But I never really learned about binders!

I figure the conservationist folk here would know better than anyone!    

I'm a smart dude and I'd be happy to read through some literature if you can point me in the right direction, to something that's just laymen enough for me to understand it while also technical enough to correctly describe the chemistries of these different alkyd binders

 (I have some collegechemistry background, doesn't have to be totally dumbed down; but perhaps not so technical that I need a masters in petroleum engineering and matsci!).

thank you again for the help,


"Slightly" underbound question

Question asked 2021-04-10 16:28:12 ... Most recent comment 2021-04-19 21:24:49
Oil Paint Drying Oils Art Conservation Topics Grounds / Priming

​Hello everyone- I am so happy to have found this resource and want to preemptively thank you for providing this information to people. 

I work in oils but haven't had any traditional training (in undergrad I did graphic design) and everything I have learned was just through self trial and error and gleaning info from friends. 

Recently I had an issue with the lightfastness of a color and through that experience learned about lightfastness which is easy enough to fix (I replaced tubes of paint) ---but it set off my anxiety brain. I wondered what else I may not know about (and the issue with learning by trial and error is what if the issue doesn't show up for years!? I used that color with horrible lightfastness for two years in a few paintings because the issue didn't show up until now.) 

So I have embarked on a journey of asking very technically-minded painters their opinions on every part of my practice and by researching on sites like this one. 

My painting process is luckily very simple which I hope will save me from huge structural issues. I actually have always just painted from the tube and have added no solvents or mediums. Much of the time a section of a painting will be done wet on wet in one layer but other times I will rework a section after it has dried. Since it's just the oil paint my understanding is I am painting only with fats and that should be structurally sound. The only times I've ever had cracking was when I really violated a thick over thin rule (like painting a relatively thin layer over a thicker color that was still tacky). In those cases the cracks showed up by the next day.

However- talking with people and stress-testing old canvases I have learned that I am not gessoing enough and that the acrylic gesso I was using is not the best quality it could be. I'm going to in the future move to using Golden's acrylic gesso and will do at least three to four layers. 

I have found that my paintings often are underbound. A finger rubbing won't do anything but if you rub them with some pressure with a paper towel the towel will be very slightly stained. 

I think going forward the better gesso (and maybe even trying oil gesso) as well as adding a tiny bit more linseed oil to my paints will help fix this issue. But I am curious about the paintings I have from the past decade of painting. This isn't an issue that has come up as the paintings aren't rubbed or placed under stress-test situations in the real world. I've sold many paintings over the years so I do have a concern about their archival-ness. 

Very long-winded but I suppose the question I am most curious about is whether there is a spectrum of unbounded-ness? If something is "slightly" unbound and kept in normal safe conditions will it be safe for at least our lifespan? (Obviously this is probably a case-by-case answer but any knowledge shared would be very appreciated)

Thank you so much for your time and insight. 


PS also am curious about fingernail tests. I've read that a way to make sure a layer is dry enough to paint over is to scratch it with your nail and if it comes off powdery and not gunky it's ready. But other people asking questions on here about the structural integrity of their work have said that their pieces aren't effected by a fingernail test as a way of proving they are sound. I may be going too intensely with my stress-tests but yes if I'm sitting there scratching with pressure over and over on a spot I can start to damage the paint. 

rigid supports, mdf vs plywood?

Question asked 2021-04-19 08:56:09 ... Most recent comment 2021-04-19 12:51:11
Grounds / Priming Drying Oils Animal Glue Oil Paint Rigid Supports

​Good morning!

I'm just getting back into oil painting and silverpoint after a 10-yr hiatus.  I got back into sculpture last year.
I'm DEFINITELY over thinking things, but that's just who I am.  I'm a very indecisive person and like to know everything about a problem! 

practically speaking, my first efforts are NOT going to need to be archival haha.  But I still want to make the right decision.

Anyway: to begin,
I have TWO use cases.

one, I'll be securing hemp canvas to a rigid backing and then using an oil primer,

two, I'll be securing the same canvas to a rigid backing and then using traditional gesso [whiting].

three... I could just prime or gesso the panel directly...

so, which is better as a rigid support for small-medium panels, say up to 8x20", probably 1/4" thick--

I see it this way:
I want to use plywood because,
more humidity resistant (mdf puffs up if it gets wet)

advantages of mdf:
dimensional stability, it is smooth and dead flat, plywood warps

I'll be making a trip to home depot in the next day or two so looking forward to your advice!  ....mdf or plywood?

I DO have three other thoughts:

there's a dude on facebook marketplaceselling 1/8" aluminum for super cheap, $70 for 3x8' (compared to $25 for 4x8' cheap plywood, so more expensive but not MUCH more per panel)..  totally archival, light weight, dimensionally stable and moisture-proof... can get bent though haha.  And harder to cut up (would need to borrow a table saw and buy a metal cutting blade, not a huge deal).  can paint DIRECTLY on aluminum too, like copper panel but much cheaper.  worth exploring?

what ever happened to painting on fiberglass canvas, which doesn't rot?  I'm having a harder time finding it for sale, but 10 years ago you could get it.  were there issues with the primer adhesion?

lastly, least if people are using a canvas mounted to a rigid support like I am... why doesn't anyone use acrylic sheet?  plastic is easy to cut, super stable and waterproof, cheaper than aluminum although pricier than plywood, and you don't need oil to stick directly to the acrylic plastic sheet if you're going to tack down your canvas first, then prime that.  

Protecting wood from moisture

Question asked 2021-04-05 16:28:27 ... Most recent comment 2021-04-05 17:56:41
Oil Paint Rigid Supports Sizes and Adhesives Industrial and Non-Traditional Products

Hi All,

Thanks to the Painting Best Practices course, I finally decided to ditch flexible canvas supports in favour of mounting linen to wooden panels. Never knew the former could be so terribly problematic! However, with this change some new considerations sprung up which need clarification. So far the preparation looks like this:

For studies I plan to use some sort of solid wood support (or maybe HDF?; but certainly not plywood because it checks) impregnated on all sides with one or two applications of 10% solution of Paraloid B72 in ethyl acetate. Then I would put some Lead Ground/Acrylic Dispersion Ground.

For final pieces I will apply the Paraloid B72 as stated above and will then use pH neutral PVA adhesive to glue the linen to a birch plywood. The linen would be pre-primed with 2x GAC 200 and some Lead Ground.

The questions are:

1) Is the aluminum foil and low-density polyethylene combination a good alternative to Paraloid B72? Should the aforementioned procedure (ironing the aluminum foil onto the panel) commence on a bare wood surface or a prepared one (Paraloid B72)? Are there concerns over this practice?

For me, the thin aluminum sheet seems to be overly susceptible to tearing, abrasion and so on. However, it can't be denied that it's the best moisture barrier. I know for a fact that there are similar alternatives such as Marvelseal 360 and alkyd-based aluminum paints. These are expensive, though. What are your take on this as a whole?

2) Does the Paraloid B72 solution have a limited shelf-life like shellac? I don't know if the one available to me has HALS/UVLS additives or not, but this is something to consider as the minimum amount sold is 1 litre. Also, can I apply Acrylic Dispersion Ground over this resinous sizing? Will the underlying varnish complicating matters as it remains redissolvable?

As a note to my last question, the potential problem I see with this practice is that solvents can penetrate into the underlayers and cause trouble when varnishing and cleaning. In any case, I decided to use solvent-based sizes over waterborne ones specifically to avoid fiber rising and warping.

3) When using solvents, can the Regalrez 1094 that has sunken in trigger the redissolution of the dried linseed oil paint or the leeching of unpolymerized free fatty acids?

This question is just me toying with an idea. I've learnt that some low molecular weight varnishes tend to sink in somewhat and that solvents, as they evaporate, can bring unbound substances to surface. My reasoning behind this notion is that the industry uses polymeric - high molecular weight - varnishes for acrylic paints because the surface is more porous than that of oil paints'. Ergo, the sinking in of varnishes is something that was found problematic, wasn't it? I'm especially interested in your stance on this one. By the way, feel free to correct me if I'm wrong somewhere.

4) Can anti-fungal agents or anti-insect products be applied in any shape or form?

Sorry if I ask too much!

Thanks in advance,

Péter Hegedűs

Recipies for making oil paint in tubes

Question asked 2021-04-03 10:57:54 ... Most recent comment 2021-04-05 16:51:03
Drying Oils Oil Paint Paint Additives Paint Making Pigments Scientific Analysis

Dear MITRA experts, I would like to ask for your advice. I want to make my own oil paint in tubes, in small batches. My neighbours have a viscous paste mixer and a tiny three roller mill for ointments. I have found formulations for many pigments, can you tell me if these will make a good paint and if it can be improved in terms of modern science and your experience? A couple of examples:

  • For Ceruleum, to obtain 100 grams of paint: Pigment blue 35: 84 grams, aluminium stearate 1.3 grams, binder 16.7 grams. For 100 grams of binder: polymerised alkali-refined linseed oil 47.8 grams, bleached poppy seed oil 47.8 grams, beeswax 1.91 grams, mastic resin 2.87 grams.
  • For Cobalt Violet Light, to obtain 100 grams of paint: Pigment Violet 49: 70.7 grams, aluminium stearate 2.4 grams, binder 29.7 grams. To obtain 100 grams of binder: Polymerised alkali-refined linseed oil 49.25 grams, bleached poppy seed oil 49.25 grams, beeswax 1.98 grams.

There is a small amount of manufacturing losses included in all recipes. The mastic and beeswax are said to be dissolved in heated oil. Would it be possible for professional artists to use this paint? How can I improve it?

Maintaining an oil painting

Question asked 2021-03-31 17:14:22 ... Most recent comment 2021-04-05 11:35:26
Oil Paint


I have a couple of questions about how to maintain an oil painting. 

I read on this forum that a painting can be dusted a few times a year with a soft brush. Is there a particular type of brush that you would recommend for this?

Also, for an unvarnished oil painting, can you explain how grime becomes chemically bonded with the paint? I wasn’t able to find any information about how this process happens. Also, once the grime is bonded can it be removed?

Thank you for your help

Zinc grounds in linen updates

Question asked 2021-03-31 17:16:12 ... Most recent comment 2021-04-01 18:09:26
Oil Paint Flexible Supports Grounds / Priming


I have been reading some of the questions on this forum from a few years ago about the concerns with zinc in oil grounds on linen. I was wondering if there were any updates or studies on how such linen may behave over time? 

I am trying to figure out what might happen to the paintings I have already completed in linen with these grounds. 

Thank you for your help

Tinted Grounds for Silverpoint

Question asked 2021-03-14 09:02:58 ... Most recent comment 2021-03-18 21:32:54
Acrylic Chalk Drawing Materials Grounds / Priming


I am currently involved in running a series of tests for an upcoming project. I want to create a series of silverpoint drawings on some uniformly tinted 5" x 8" HDF panels. For the dark values in silverpoint I want to achieve a mid to three quarter tone gray (but no more), which I imagine touching up with some white highlights as a final touch. 

So I'm trying to decide what is the best way to prepare the ground, do I go traditional (chalk gesso) or modern (acrylic)? 

For to the acrylic direction, I have already created two tests: 

One is a smooth yet absorbent HDF surface prepared with Golden Acrylic Gesso (which I have tinted using acrylic tube paint). 4-6 coats. Lightly sanded inbetween to remove brushstrokes. The tint is good. Over this I brushed a layer of (transparent) Golden Pastel Ground. The result is very toothy and feels like rough sandpaper. Nice. The silverpoint test marks I have made appear to be darker than usual. Thus there appears to be sufficient contrast between the silverpoint and the tinted ground. I imagine touching up the highlights using a white gouache, but havent't tried it yet. Will there be any absorbency issues with that? Should I use acrylic paint or is gouache OK?

The second test is on a smooth yet absorbent HDF surface prepared with Golden Acrylic gesso over which I brushed Golden Silverpoint Ground. This time the acrylic gesso was untinted because I knew I would be introducing the tint through the Golden Silverpoint Ground - which is opaque. The result feels less toothy to the touch, (actually it feels like smooth plastic), but does appear to take the silverpoint test marks well enough. Made repeatedly thgese could become the mid-value gray tonality I seek? I haven't tried the white gouache highlight test here either but my questions are the same. Will there be any absorbency issues with that? Should I use acrylic paint or is gouache OK?

However, my main question concerns the traditional approach. If I were to go that direction using RSglue/chalk gesso, I imagine adding some terra verte and maybe a small bit of burnt umber to my gesso ground prep. This would achieve the tint I am looking for. And if these dry pigments were less than 10% by volume (surely it would be even less than that) I think that these should be no problem to the integrity of the gesso. Is that correct?

In addition, I am wondering if there is a way increase the tooth of the traditional chalk gesso ground so as to increase the value of the silverpoint marks? Marble dust or other additives, etc...? Coarse sanding of the final surface? Any suggestions? 

Thanks for the feedback. I really appreciate being able to ask my questions of well informed resources.

Combining Acrylic over graphite

Question asked 2021-02-11 10:35:28 ... Most recent comment 2021-03-16 17:54:32
Acrylic Drawing Materials Paint Additives Paint Mediums Pencil Varnishes

​Hello dear people from Mitra!

I have a question regarding mixed media basically. 

If i have a fully rendered graphite pencil drawing on thick watercolor paper (with all details and deep shadows done, it has a lot of graphite on it) and i want to paint over that with acrylics , what is the best and safe way to do that? 

Is it enough to just put a layer of a clear Matte Medium and than to paint over that with acrylics? 

Or is it safer to first put a coat of Pastel, Charcoal Fixative ( it is Talens Fixative and it contains :  Colourless resins, ethanol ) and i think it is workable fixative,   and then to paint with acrylics and to use a acrylic matte medium in it? 

Thank you in advance and i hope you are all ok and safe during these times.

Kindest regards

Marko Karadjinovic


Question asked 2021-03-15 16:40:13 ... Most recent comment 2021-03-16 11:42:15
Art Conservation Topics

​I am applying diluted Jade 403 to acrylic paint to the the cracked/damaged areas before retouching. Can anyone recommend how diluted the pva(Jade) should be and if it is a good idea to apply more than one coat. 

Mysterious Discoloration

Question asked 2021-03-12 10:21:44 ... Most recent comment 2021-03-15 15:06:14
Oil Paint

​Hi Brian, thank you for your response. Very astute of you to ask about storage. My panels were stored for several months in vellum envelopes in the mostly dark storage racks of my studio. I always thought only lead based materials would yellow. So I was surprised when I saw the extent of yellowing on these paintings. 

I used a fair amount of medium on the Titanium white paint for the backgrounds. The paint I use is this luscious, rich, Italian paint, but quite stiff out of the tube. 

Why RSG? I smile as I write this- I'm old school! I was trained in the 80's and 90's art schools, and that's what we were taught. I haven't had problems before, but of course, I am open to updating my methods. 

Thanks! Maryam

Mysterious Discoloration

Question asked 2021-03-11 21:28:29 ... Most recent comment 2021-03-14 21:35:21
Oil Paint

​Hello MITRA forum, I just experienced an oil painting disaster. A series of oil paintings with Titanium white backgrounds yellowed and dulled after several months in my studio storage. Where did I go wrong?! Was it my ground? Oil paint pigment? Medium? Varnish? All of the above?! These are the materials I used: 

1. RSG sizing on portrait linen over maple board.

2. Acrylic gesso ground (100% acrylic polymer).

3. Titanium white oil paint for the subject backgrounds. Paint tube notes Titanium Dioxide in safflower and poppy oil.

4. Neo Meglip medium. Described as a contemporary version of Maroger. Contains Petroleum Naphta.

5. Satin archival varnish. A mineral spirit acrylic aerosol w/UVLS. The fine print notes contains: Acetone, Propane, N-butane, Petroleum Distillates, Solvent Naphta, Trimethylbenzene.

Thank you for your thoughts!


Golden Polymer Varnish for Egg Tempera

Question asked 2021-03-05 21:47:38 ... Most recent comment 2021-03-12 08:09:01
Egg Tempera Varnishes

​I'm looking into using Golden Polymer Varnish on my egg tempera icons. What would be the drawbacks of using this varnish?

In my experience, other varnishes cause FAM or blooming (I think the solvents in oil-based varnishes aggravate the lipids, especially Gamvar). Golden Polymer Varnish is the only water-thinnable varnish I've found that is also reversible/removable (Lascaux doesn't seem to be reversible, at least that I can find...or is it?). Golden does not seem to cause immediate blooming in my tests, even on new paint swatches a few days old (not that I plan to varnish that soon). Reversability is important to me since it is quite likely for an icon to get lipstick on it eventually, if not oily spot, etc.

I like the look of the matte surface as it is quite similar to the egg; the gloss looks fantastic over the gold. A Golden technical expert said to use the gloss first to seal it, then use the matte over top for the final sheen. So, I can cover the entire icon (gold and tempera) with gloss, then cover only the tempera with matte. The entire surface is then protected and removable.

I've also seen in another thread the recommendation to use Krylon Crystal Clear as an isolation coat. I'm a little worried about orange peel, to be honest, but I think that's worth looking into as well.

Also in another thread was the concern about the alkalinity of this varnish. Would that negatively interact with the egg tempera? The expert at Golden said they do not recommend the Polymer Varnish for oil paint. The binder in tempera is a drying oil. Will this be problematic?

Thank you for your help.

Brian Matthew Whirledge


Linen canvas and GAC 200 question

Question asked 2021-03-07 05:51:14 ... Most recent comment 2021-03-11 04:48:52
Grounds / Priming Flexible Supports Oil Paint Sizes and Adhesives


Some new questions sprung up thanks to covid and Brexit (I get my stuff from GBR to EU). A 450 GBP packet now costs 140 GBP just to deliver to Hungary. Before Brexit, large shipments such as this were gratis or cheap at minimum... I am not here to rant, just wanted to take stock of the unfortunate situation.

Do you happen to know good and trustworthy canvas brands and retailers, preferably in the EU? Artfix is pretty widespread here, but markedly costlier than the others. I would like an artist's grade linen canvas that is also not prohibitively expensive.

Secondly, is it worth to save money (even 140 USD!) by buying a medium textured canvas instead of a fine one? Or is it less archival for being more porous/more loosely woven? I will do portrait stuff, by the way.

With regards to sizing, I'm planning on getting the GAC 200, which is proposed by Sarah Sands (2 very thin layers) and the tech support guy I talked to. However, on Golden's webpage it says it's not recommended for flexible supports.* I firmly trust the people from Golden (more than the webpage), just wanted to double check if someone can reassure me that it is adequate. :) *Note: I will further apply 2 coats of Golden acrylic gesso and 1 layer of Rublev lead ground, so the GAC 200 will not be used alone, if that matters.

By the way, are unused credit cards ok for the thin application of sizes/grounds?

Thanks in advance!

Hope you're all well,

Péter Hegedűs

Acrylic dispersion ground adhesion problems with acm panel

Question asked 2021-03-07 06:08:25 ... Most recent comment 2021-03-09 02:34:43
Acrylic Grounds / Priming Oil Paint


I'm an oil painter that has had good experiences with using ACM panels with an acrylic dispersion ground as a substrate to paint on. However I noticed some adhesion issues with the last batch of panels I primed and was wondering if anyone has any advice on how to move forward, things to consider etc..

My process for preparing the ground has been as follows;

1) Lighlty scuff/sand the polyester surface of the ACM panel making sure not to sand down to the aluminium surface.

2) Clean the surface with 97% Ethanol

3) Apply a first layer of Golden Acrylic 'gesso' mixed with GAC 200 in a ratio of roughly 60/40 - 70/30

4) Leave to dry for 24 hours

5) Apply a second coat of the Acrylic 'gesso' with a little bit of water added to improve consistency for easier brushing on the primer. (Max 10% of water) I don't measure those amounts precisely, doing just by feel.

6) leave to dry for 24 hours

7) Repeat steps 5) and 6) 2 times.

8) Finish the ground with a layer of pure Golden acrylic gesso, no water added.

I live in Belgium and prepared these panels last month when it was pretty cold (wintertime) although the temperatures in my studio were normal room temperature during the day. During the nights it will have beeen colder however, so some temp fluctuation will have occurred. I left the panels to dry for 2 weeks and performed an adhesion test on one of the panels by crosshatching with a blade making little 1/10 inch squares and applying a piece of ducktape and swiftly ripping it off. Result: over 50% of the primer stuck to the tape and came loose...

If I take a palette knife and scratch the side over the delaminated area trying to remove more paint I have to apply some pressure to scratch it off, so there is some amount of bonding but I'm not happy with that result. 

How to move forward? Will all of these recently prepared panels be totally unsuitable to paint on? Do I have to worry about more severe delamination of the painted surface in the future? What risks do I take when painting on this surface? Are there ways to improve the current state of the grounds without completely sanding off all of the layers and starting over? 

Any advise highly welcomed and appreciated. 

Kind regards,


restoring wood and canvas sculpture painted with acrylic

Question asked 2021-03-04 17:55:48 ... Most recent comment 2021-03-04 18:36:45
Art Conservation Topics

​I am wondering if there is any concern/issue of compatability using fluid acrylics over older acrylic paint.  There is a lot of cracking both on the painted wood and painted canvas. Also, if anyone has any suggestions about matching colors, I am open to that- but less critical (I'm not a trained painter! Or restorer for that matter.)

Painting with gouache on panels

Question asked 2021-02-27 13:00:10 ... Most recent comment 2021-03-02 12:34:57
Gouache Grounds / Priming Pigments Rigid Supports

I would love to hear any thoughts from a conservation standpoint regarding using gouache on prepared rigid surfaces. I paint with gouache (I typically use Holbein or Turner acryla gouache for their flatness and opacity, but have experimented with different brands) on gessoed cradled panels, either baltic birch or hardboard. Since gouache is water-soluable (though I find that the acrylic gouache is less inclined than artist's gouache to reactivate with moisture), I'm curious about whether it would be advisable to add some kind of finish to the board after the painting is done. I've experimented with a few different varnishes, but I know these kinds of finishes can be problematic, and I also don't like how the varnish changes the surface of the painting... even matte ones add some kind of sheen. Is there a way to add a level of protection from light and moisture to gouache works on panel without framing/glazing them? Thanks for any opinions.

Stand oil gone hazy/foggy

Question asked 2021-02-25 15:34:37 ... Most recent comment 2021-03-02 06:02:00
Oil Paint Drying Oils Storage



In the picture above, hopefully you will se the haziness I am talking about. I don't know if this is ok? It developed little spots of "opaque smudges" everywhere. The stand oil was not exposed to direct sunlight. 

Another similar question is that W&N satin metacrylate-based varnish is expected to settle down, right? With this one I am not so much concerned because it has to be shaken well before use anyway. 

Thanks for your input! 

Péter Hegedűs

Oil Paint Thickeners

Question asked 2021-02-28 16:26:37 ... Most recent comment 2021-02-28 20:16:05
Oil Paint

​With some pigments my oil paint slumps.   I use Tixogel VZ, Aluminum Stearate, wax, and fumed silca.  I use a ball mill with acetone and linseed oil to grind the pigment and then evaporate the acetone.  I find with a pigment like ultramarine blue I still have problems.  The oil also separates from the paint in the tube.  I just don't know how much of anything to use or how to use it.  I grind the Tixogel VZ into acetone first, that is about all I can find on how to thicken.  Thanks for any input.  

DTM Bonding Primer by Sherwin Williams - presence of zinc

Question asked 2021-02-24 01:07:40 ... Most recent comment 2021-02-26 17:45:54
Art Conservation Topics Grounds / Priming Scientific Analysis

In a number of places you recommend DTM Bonding Primer by Sherwin Williams as a ground, particularly for use with aluminium panels. 

The EDS data sheet suggests it contains zinc.

Zinc (as Zn)             2% by weight

Zinc Compound      3% by weight.

In dry form the percentage of zinc will be much higher. 

Yet elsewhere you frequently warn to check for zinc content. For example in your Grounds and Primers technical resources state: '​Zinc white has been found to react with components in oils and alkyds and form “metal soaps,” which in turn can give rise to delamination, wrinkling, the formation of white-colored aggregates, and the softening of ground/paint layers. Research is presently being carried out to determine the extent of damage that can occur when these materials are present.'

Can you please clarify? Is the zinc in a different form or are there other reasons why this product is suitable despite the presence of zinc? Have I misread the EDS - I'm not a chemist! There are a number of people on my forum (Wetcanvas) discussing this and we are interested in the clarification. 

Zinc white detection

Question asked 2021-02-22 07:48:52 ... Most recent comment 2021-02-25 16:51:01
Oil Paint Pigments


It has already been written quite a lot about problematic nature of Zinc white in oil. In case one is not sure about partcular oil color composition (e.g. no pigment info on a tube, or no longer existing company, or just customer service not answering to questions), is there any way how to detect the presence of zinc white? 

Kremer pigmente offers various chemicals

Is it possible to use some sort of chemical (liquid, powdered) which, when mixed with paint, will react with zinc white in a certain way (for example the hue of paint will change) and therefore prove its presence even if it is present in small amount?

DTM Bonding Primer by Sherwin Williams - presence of zinc

Question asked 2021-02-23 21:41:29 ... Most recent comment 2021-02-23 21:32:00
Art Conservation Topics Grounds / Priming

In your reference materials on Grounds and Primers you are very clear about the need to avoid zinc: "zinc white has been found to react with components in oils and alkyds and form “metal soaps,” which in turn can give rise to delamination, wrinkling, the formation of white-colored aggregates, and the softening of ground/paint layers." 

On several places on this site you recommend DTM Bonding Primer by Sherwin Williams, particularly for ACM. 

The EDS data sheet suggests it contains zinc:

Zinc (as Zn)             2% by weight

Zinc Compound      3% by weight.

I'm not a chemist but a group of us at Wetcanvas forum are seeking clarification. Is this zinc in a different form that doesn't create problems? If so what forms of zinc do not need to be avoided? Have I misinterpreted the EDS?

Preparation for hardboard - understanding the questions

Question asked 2021-02-22 03:17:10 ... Most recent comment 2021-02-22 20:53:29
Art Conservation Topics Alkyd Grounds / Priming Rigid Supports Scientific Analysis

I usually paint on hardboard/masonite. I want to strengthen my conservation preparation which includes: a) Best techniques /materials; b) Understanding the questions and answers. 

I have been recommended Zinsser Cover Stain (VT Styrenated Modified Alkyd, Calcium Carbonate, Magnesium Silicate, Titanium Dioxide.) It would be really simple if it worked. But I'd definitely take proven methods over ease of use and possibilities. 

I’m trying to understand the questions. 

(1. The painting surface: (canvas, board, plaster wall) needs to be resistant to movement (expansion/contraction or bending), moisture, degradation (breaking down of the material) or release of chemicals. For masonite I build a cradle to keep it firm. Sometimes they need sealing. Chemical stability is a plus.

2. Barrier (size/etc): Some surfaces need sealing to minimise moisture absorption, moulds, etc and to stop it leaching chemicals into the painting. This barrier is best if it’s chemically stable including pH neutral. 

3. Ground: Oil paints need ‘tooth’ to grip a surface for a) Easier laying of paint; b) Sufficient adhesion to avoid peeling down the track. Best grounds will be very stable so that they don’t leach chemicals or react with the oil or the pigments, and stable so they don’t break down. All the ingredients. It also shouldn’t be too absorbent of either pigment or oil.


I’m trying to understand the questions:

1. The painting surface: (canvas, board, plaster wall) needs to be resistant to movement (expansion/contraction or bending), moisture, degradation (breaking down of the material) or release of chemicals. For masonite I build a cradle to keep it firm. Sometimes they need sealing. Chemical stability is a plus.

2. Barrier (size/etc): Some surfaces need sealing to minimise moisture absorption, moulds, etc and to stop it leaching chemicals into the painting. This barrier is best if it’s chemically stable, including pH neutral. 

3. Ground: Oil paints need ‘tooth’ to grip a surface for a) Easier laying of paint; b) Sufficient adhesion to avoid peeling down the track. Best grounds will be very stable so that they don’t leach chemicals or react with the oil or the pigments, and stable so they don’t break down at molecular level, crack, movement etc. All the ingredients. It also shouldn’t be too absorbent of either pigment or oil. 

Questions: 1. What is the best proven preparation for board for conservation? 2. Where can I find the research-based material to build a basic understanding of the correct questions/criteria? Is my list close? 3.  Zinsser cover stain - I gather there are variations in VT Styrenated Modified Alkyds - is there a view on this product or similar? In some ways I'm interested in asking their technical team the right questions. The test of time it hasn't passed, I know. 

venetians schools 6-9 coats of size/primer for linen canvas

Question asked 2021-02-20 19:32:59 ... Most recent comment 2021-02-22 11:44:26
Animal Glue Grounds / Priming Flexible Supports Sizes and Adhesives

​Hello Mitra,

I read a while back that since the venetian school was painting on linen, and not wood, that they had to put less coats of size and gesso on their canvases.  Something along the lines of 6-9 coats.   These size coats and gesso coats (gesso sutile) were done thinly too.  This was done so that the size and gesso wouldnt crack due to the flexibility of the canvas.  I also read that this was also one of the reasons they went thicker with their paint.  The thicker paint served as an extra protection from the atmosphere.

Are 6-9 coats on linen fine?

Best Regards,


sun thickened and studio thickened linseed oil for mediums

Question asked 2021-02-20 07:59:11 ... Most recent comment 2021-02-20 10:11:20
Paint Mediums

​I refined my own linseed oil (from flaxseed oil). It was my understanding that you could 1. put it in a jar in a studio window and age it; 2. put it in a tray in direct sunlight for a period of time then put it in a jar. These have now become very viscous. I thought this was good; that it had become "stand oil". But reading the Mayer book, I think he says this oil is oxidized and cannot be used due to high likelihood of more yellowing. I believe the people at Natural Pigments said thickened oil has to be heated, not just aged. So my question is: is this 'studio/outdoor thickened' oil useless? I would have to mix it with thinner oil or solvent to use it.

Correcting an overly dark undercolour in Imprimatura

Question asked 2021-02-18 02:26:56 ... Most recent comment 2021-02-19 21:21:45
Oil Paint

​Dear MITRA staff I  was informed by my teacher about a process he referred to as "double Improimatura" in which one starts with a coat of Venetian Red oil paint or similar (thinly applied) followed by a light grey layer, which should be scumbled over the top. This was supposed to create an opalescent kind of grey. However despite using very thin layers, I've found the Venetian Red is quite dominant and I'm concerned about it showing through more and more over the years as I know oil paints become increasingly transparent over time. Needless to say, perhaps, I probably will not use this procedure again!--or if I do it will be with a much, much lighter and more translucnet undercolour than Venetian Red. In the meantime though I would like to salvage the panels I've treated in this way, to whatever extent is possible. Multiple, very thin, scumbled/scrubbed on coats of Lead White mixed with a light grey (composed of palette scrapings neutralised to a grey colour) haven't subdued the VR to the extent I would prefer so I thought I should do some more scumbled "layers" with some titanium thrown into my grey mix, given that it has more opacity than Lead White. I dont want to compltely obliterate the VR, just for it to be welll subdued so that my grey remains fairly grey not a grey-sprinkled dull pinky colour. BTW I am prepared for the fact that all these panels may need to be considered suitiable only for studies or master copies, given that the prognosis in terms of overall darkening may be rather dire. Would this be an appropriate level of pessimism to have? Is my plan--to continue with a couple more scumbles, this time with some Titanium White added as noted above-- if executed with due regard to fat over lean (flexible over inflexible) principles and if pplied in the same very thin, scrubby scumbly way, reasonable? 

A quest for long-lasting stretched linen surface

Question asked 2021-02-14 19:21:52 ... Most recent comment 2021-02-17 07:24:19
Oil Paint Sizes and Adhesives Grounds / Priming Flexible Supports

​Hi all,

I would like to create the most archival stretched linen surface for oil painting, as far as my budget allows it.

First of all, I plan to use lead ground in the last one or two layers in the process. However, I was thinking about including acrylic grounds, so that I don't use up the expensive lead ground that fast. However, there seems to be a division in the art world, where some swear by the use of sizing before lead grounds, whereas others just apply four coats of acrylic gesso. Again, I've also heard on the wetcanvas forum, that acrylic gesso alone will leave the canvas susceptible to deterioration from the back (because canvas is not sized). The implication for me in this case is that maybe I should use some sort of sizing (PVA, GAC etc.), then acrylic gesso and then the lead ground, for the utmost archival property.

At the end of the day, my question is basically: how to prepare the most archival lead ground without necessarily breaking the bank?

Some guidance would be very much appreciated!

Kind regards,

Péter Hegedűs

Repainting a plaster statue with oil paints

Question asked 2021-02-13 14:35:55 ... Most recent comment 2021-02-14 22:46:45
Oil Paint Other Rigid Supports Sizes and Adhesives

If you were repainting a large old plaster statue (the corpus from an old church crucifix from 50+ years ago) using oil paints, would you apply a sizing? I've been thinking that once I've removed all of the old paint and fixed the fine cracks, I'll use an oil paint primer like those used to prep plaster walls. Does this seem like a good plan? I’d love any advice you could share.​

Sunflower oil?

Question asked 2021-02-14 12:50:24 ... Most recent comment 2021-02-14 21:33:06
Oil Paint

​I live in Turkey and I need to paint now using non toxic materials. For cleaning brushes ,  I am using sunflower oil  will this cause problems. 

flattening a little dimple in an oil painting

Question asked 2021-02-07 23:55:34 ... Most recent comment 2021-02-08 19:32:53
Art Conservation Topics

​I have a oil painting with a s 1/4" dimple in the corner of the painting. There is no noticable damage to the canvas, from the back. The paint is slightly damaged but no paint is missing.

I used a little distilled water on the back of the canvas and about 1/2 of the indention came out. 

I hate to reline the whole canvas to eliminate the indention.

Any thoughts are appreciated.

Dating a vintage copy of Hals Baffoon

Question asked 2021-01-27 12:20:07 ... Most recent comment 2021-02-08 18:52:36
Art Conservation Topics Scientific Analysis Oil Paint

​I have a vintage copy of Franz Hals "Baffoon with a Lute". I would like to estimate the age of this copy.

I have included photos of the stretcher, mounting tacks, back of the canvas, sides of the canvas, and a couple of pictures of the front of the painting.

It was in a frame made in the 1960s, but I think it is older than that. It appears to be in the original stretcher. The mounting tacks are not "blued" and they have rough shaped heads of different sizes.  The back of the canvas is not white but has white spots that may suggest it is soiled. The painting does not appear to have been varnished. It is darker than the original "Baffoon" and has slightly less detail. The decoration on the hat is different than the original "Baffoon".

Any suggestions on how I might date this copy would be appreciated.01 Hals canvas back 1.jpg02 Hals mounting tack side 1.jpg03 Hals mounting tack heads 2.jpg04 Hals front corner and edge.jpg05 Hals front texture of hand 1.jpgBaffoon Front View.jpg

Egg Tempera on Casein

Question asked 2021-01-21 18:32:56 ... Most recent comment 2021-01-29 08:56:29
Egg Tempera Casein

​I have a student wondering if she can paint egg tempera on casein.  Since casein, like tempera, is a high PVC paint, I can imagine it's open, absorbent surface may allow tempera to properly adhere. But I don't really know.  Any thoughts on this idea?

Koo Schadler

casein-acrylic binder as a size for priming linen?

Question asked 2021-01-08 05:47:32 ... Most recent comment 2021-01-25 15:41:08
Casein Sizes and Adhesives Grounds / Priming Oil Paint Flexible Supports

I'm looking for the best way to size my linen, when using a lead-oil ground. 

A combination of Golden GAC 400 en GAC 100, or 2 coats of GAC 200 gives good results. However, I have also tried casein-acrylic binder by Ara Colours ( They are a part of Old Holland.

The descrition says: "Casein acrylic binder V350 is a modern alternative to rabbit glue. It gives a strong flexible film for the preparation of the canvas. Casein acrylic binder is insensitive to moisture after drying."

It becomes indeed very stiff (much more than the GAC 400 or 200) even after a year or so, which is probably due to the casein. This stiffness is very desirable of course, but I also read that casein becomes brittle. Is it possible that this brittleness is counterbalanced by the acrylic? And is casein-acrylic able to block oil absorption? So, can casein-acrylic binder be a good size if you want you painting to last?

I have mailed Ara Colours several times with this question about how it works, but never got an answer, so I hope someone can help me here.

Protein Denaturation

Question asked 2021-01-17 08:28:02 ... Most recent comment 2021-01-19 21:30:04

​Hello MITRA,

I have an egg tempera student with a background in icon painting who makes her medium by combining 1 part yolk with 2 parts wine.  For my class, she changed the ratio to 1 part yolk to 1 part wine (since I work with a thicker medium).   

I'm not a fan of adding alcohol to medium: I prefer just egg yolk and water (cracking a fresh egg as needed; and adding isopropyl alcohol only to the few colors that actually need help dispersing).  The simpler a paint system is the less that can go wrong, and the easier problems are to diganose.  But I realize many painters are used to adding wine or vodka to medium, and of course they are free to work as they please.

This morning her medium, which she keeps refrigerated when not in use, had "curdled". I explained that this is (I believe) protein denaturation: alcohol is causing the molecular bonds in the protein portion of yolk to break down, the same as cooking an egg.  

So, two questions: 

1. Why doesn't this happen everytime alcohol is added to egg yolk?  Does egg oil sort of "encapsulate" the proteins and protect them from the denaturing effect of alcohol?  I understand there is less protein in yolk than in egg white, but still there is some, and clearly (from her example) it's capable of denaturing.

2.  Any guesses what casued her medium to denature?

Hope some of you chemists out there can shed light on this.

the vulnerability of traditionally gessoed ground to water media

Question asked 2020-12-17 05:39:47 ... Most recent comment 2021-01-17 16:13:26
Grounds / Priming Gilding

​Hello Mitra... so happy to have stumbled onto this forum via Koo Schadler's website. 

I've been dipping into the world of water gilding and have a strong desire to begin using it in my painting. 

The process I've been considering and experimenting with is as follows:

Cradling 1/4" plywood panel. 

Coating panel twice, front and back, with Zinser white shellac

After lightly sanding surface applying linen gauze soaked in 15% RSG

application of 10% RSG /Bologna chalk gesso (8-9 coats)

application of white kaolin clay and titanium dioxide white (10:1) with 10% RSG (6 coats)

*But now this is where things get tricky... I would like to paint onto the surface very loosely with water media, (Golden High flow acrylic) before water gilding the whole surface and bringing it to a high polish, then removing the gilding where I want to reveal the under painting, coating it with Golden MSA varnish and a coat of GAC 100 before I oil paint on top of the entire thing.... I know, talk about over-complicating things. 

My questions are:

Does this process raise any red flags for soundness and archivability? Even though loosely water painting onto the kaolin surface does not appear to cause any issues, I worry about the soundness of the gesso after I've wet it? I'm stuck on using traditional gesso because I'm looking for the high polish the kaolin provides. Unfortunately any ready made bole products I can find here in europe aren't white enough.... even with the addition of 1/10 titanium. 

Another concern is the ability of traditional gilding liquor to adhere the leaf considering I've now covered it with a water-thin layer of acrylic? I've noticed on some websites here in Italy that they use fish glue to adhere the leaf after traditional gesso prep. I've since secured some Isinglass (Selinski) and I'm wondering if this is a sound way to adhere the leaf that will allow a true burnish? Should I apply a coat of glue and let it dry, then apply the leaf in a normal fashion with gilder's liquor? Plus I honestly have no idea how to prepare the glue or at what strength I should be using it.

Any expertise and help would be greatly appreciated. Just hoping I'm not completely off my rocker on this one, because I've been working for well over two years to nail this process and I'd hate to give up at this point, but I keep running into archival walls and I'm beginning to doubt that what I want to achieve is doable. 

Patching painted canvas that will be painted over

Question asked 2021-01-09 13:20:07 ... Most recent comment 2021-01-14 20:05:06
Oil Paint

​hi!  I have two oil paintings with scuffed/torn corners.  One is obvious on the actual piece and I would like to paint over it, but am worried that the scuff has gone to the canvas layer and oil may rot the area of the corner.  The other is on the sides of the canvas, but I was hoping to paint all around the sides as well.  Those have definitely gone past the gesso layer and exposed the raw canvas.   The one that is on the image was done in February 2020, and the other in May, although I recently started painting on that one again before I noticed the tears.  

any advice how to safely patch these areas in a timely manner so I can paint over them sooner than later would be very helpful  thank you!


5CF27B39-69A9-4F49-B340-D10287139165.jpegps. I am new to the forums so I apologize if this has been asked. I did search but couldn't find anything on it.

Repairing a Vintage, Plank Backed Picture Frame

Question asked 2021-01-10 17:04:03 ... Most recent comment 2021-01-13 11:24:23
Art Conservation Topics Matting, Framing, and Glazing Rigid Supports

​I am conserving a vintage frame constructed of pine, where the mitered corners have developed gaps as wide as 1/4" and where the frame has warped to about 2" from flat. It is a heavy 36" x 34" frame. The frame had 3/4" pine planks professionally tapered and glued to the back on all sides. 

I had to removed the backing planks to enable closing the gaps on the mitered corners. When I removed the backing planks, the warping was corrected. 

I would like to leave the backing planks off once the frame is properly repaired, but if they were part of the original frame fabrication, I should probably reinstall them. If they were added later to stabilize or strengthen the frame, I would likely leave them off.

I believe the frame was fabricated before 1950. It frames a hand painted copy of Hals "Baffoon Playing a Lute" that was possibly painted between 1880 and 1900.

Question: Do you know of a framing technique where planks are glued and nailed to the back of a frame to provide structural strength, either during original frame fabrication or to stabilize a frame at some later date?

Any recommendations would be appreciated.

Frame Front.jpgFrame Backing Plank Construction.jpgFrame Corner Misallignment 2.jpg


Museum mounting kit

Question asked 2020-12-14 18:11:35 ... Most recent comment 2021-01-11 11:28:05
Matting, Framing, and Glazing Art Conservation Topics

Lineco makes a product called the “Museum Mounting Kit” to make conservative mounting images easier. Do you consider this kit to be able provide true conservative mounting? If so how do think it compares to mounting techniques such as strips and corners that prevent any type of adhesive contact with the artwork?

Using Spray Fix on Charcoal for an oil painting

Question asked 2021-01-03 02:32:26 ... Most recent comment 2021-01-06 17:06:36
Oil Paint


I've heard of painters using spray fix on primed canvas ( (both oil and acrrlic ground) to fix a charcoal drawing before painting on top with oil and have assumed this could be problematic with potential delimination issues, but trying to gauge if this is overly cautious as long as the spray fix is applied reasonably thinly. 

Does Mitra recommend a best practice here for proceeding from a charcoal underdrawing? How is this issue different if the ground is oil based vs. Acrylic gesso? Are there better fixatives suited for this purpose if it is not to be avoided altogether?

Forgive me as I've seen this touched on in these forums, as in here,

but feel like I am still missing info on this general topic here.

Happy New Year- Best, T

Cleaning old and unvarnished paintings

Question asked 2020-12-30 09:58:43 ... Most recent comment 2020-12-30 21:04:03
Oil Paint Art Conservation Topics

​What is the best way to clean old, unvarnished oil paintings in Belgian linen that have been affected by mold, dust, and some bits of paper stuck on some of them? These paintings were covered in glassin paper, parchment paper, and some in Manila paper and have been in storage for years. 

Also, it seems that most of the dusty white and ghostly appearance isn't really mold but something else. This haze effect is visible in the dark areas where the earthy colors are, but never in the lighter areas. Also, the backs of the paintings are very clean. So, I'm not sure if it's mold and how best to address this. I'm seeing so many conflicting advice online.

Note: I'm unable to go to a professional art restorer at this time, so will have to do everything myself. Please help. Would appreciate any advice. Thank you! 134152164_10157907941582358_7668322117097742284_n.jpg 

Cleaning old and unvarnished paintings

Question asked 2020-12-30 09:50:48 ... Most recent comment 2020-12-30 09:47:00
Art Conservation Topics Oil Paint

​What is the best way to clean old, unvarnished oil paintings in Belgian linen that have been affected by mold, dust, and some bits of paper stuck on some of them? These paintings were covered in glassin paper, parchment paper, and some in Manila paper and have been in storage for years. 

Also, it seems that most of the dusty white and ghostly appearance isn't really mold but something else. This haze effect is visible in the dark areas where the earthy colors are, but never in the lighter areas. The backs of the paintings are very clean. So, I'm not sure if it's mold and how best to address this. I'm seeing so many conflicting advice online.. Please help! Would appreciate any advice. Thank you!

Reducing absorbency of acrylic primer

Question asked 2020-12-13 10:56:03 ... Most recent comment 2020-12-14 15:13:47
Rigid Supports Sizes and Adhesives Flexible Supports

I'm using an acrylic primer to prime an MDF panel for subsequent (possible) acrylic underpainting, then ultimately oil painting.​ I've previously had problems with such surfaces "grabbing" the brush, making it almost impossible to blend paint nicely, as well as the paint drying out very fast/oil colors sinking in. I've heard two different bits of advice:

  1. Use PVA to seal the primer by applying a thin layer. 
  2. Use egg white, spreading it thinly and allowing to dry before painting.
I've tried acrylic medium before, but I found that it didn't improve the brushability all that much, it still has a certain "grab" to it.
Would either choice be better? Also, would the same advice hold for flexible support?


Question asked 2020-12-14 00:24:34 ... Most recent comment 2020-12-14 12:43:27

​Iis it ok to spray fixative on drawing paper BEFORE I do the pencil drawing? Reason: I like the graphite, which I use in tones, not lines,,to be be sometimes brushed to make lighter areas and also. I dont use workable fixative to do this but final fixative, and also to make the drawing easier to erase 

repair split at side of oil painting

Question asked 2020-12-13 07:53:42 ... Most recent comment 2020-12-13 17:35:39
Art Conservation Topics Oil Paint

​A painting of mine got into a show and I just noticed a weakening and the beginning of tearing at the back/side of the canvas. Can this be repaired without strip lining? And if so, how.

Water Block on Gesso

Question asked 2020-10-21 11:26:55 ... Most recent comment 2020-12-11 09:30:26
Animal Glue Egg Tempera Grounds / Priming Rigid Supports

​Hello Mitra!

I wonder if anyone here has experience with "water blocking" traditiona gesso on panel? I've seen very little about it, but I've read some suggestions that a gesso panel could be smoothed by working the surface with a hardwood block dipped in water.

It's hard for me to imagine this method fully removing brushstrokes, and I would worry that the paste worked up by the wet block would be unstable.

That said, the intorlerable amount of dust created sanding larger gesso panels has me searching for alternatives.

Perhaps an old school scraping method combined with a wet block?

If anyone has experience or resources to share on this topic, I would love to hear about it. Thank you

- eli bornowsky

Varnish beading up in places, on acrylic?

Question asked 2020-12-08 16:25:50 ... Most recent comment 2020-12-09 08:00:28
Acrylic Art Conservation Topics Scientific Analysis Varnishes

Hi all,

I recently varnished two paintings I completed that were in acrylic. One was in Golden OPEN which I had left to dry for several weeks and with using undiluted Gamvar Gloss it varnished beautifully with no issues.

The other painting was done with Amsterdam Standard and Liquitex Basics Acrylics (So not craft art products) that I left to dry for 2-3 weeks. But to my surprise I found that I had beading in some areas as I would with oil paints. I scrubbed with the brush to reduce the surface tension until the varnish applied properly (or mostly).

Still, I was surprised as I've not had this happen with acrylics before and I assumed that the relatively open surface (compared to oils) meant that beading couldn't occur.

Have you had this experience before when conserving acrylic paints? Is there anything you recommend I could do in the future to avoid this? It was interestingly how the other painting was completely fine though. Would it be the difference in the resins between the different companies products that contributed to this? If so, then perhaps an isolation coat with GOLDEN mediums (following their guidance) would resolve this?

Just interested in your thoughts..

Richard Phipps

Canvas on Masonite

Question asked 2020-12-08 21:57:57 ... Most recent comment 2020-12-08 22:14:51

​I want to adhere pre-primed canvas to masonite panels using acid free PVA glue. The panels are smooth on both sides.  Can I simply glue the canvas directly to the masonite as is or do I need to prep the surface in any way such as cleaning, sanding or priming?  (When I adhere canvas to plywood I seal it on all sides with pigmented shellac and then use acid-free PVA glue to attach the canvas so I may be just over-thinking this.)    

impasto oil rises to the surface

Question asked 2020-12-07 20:56:40 ... Most recent comment 2020-12-08 21:30:30
Oil Paint

​Many of my paintings are done in thick impasto oil paint using stand oil. I have done some testing (2 years ago) using different stand oils in impasto oil paints. I have noticed the oil rises to the surface and yellows slightly. When the dried oil is cracked open the paint is a bright white inside. I have tried poppy oil and even though that rises to the surface it does not yellow, but I noticed the paint is more brittle than those done with linseed/walnut stand oil. So my question is how to prevent the oil rising to the surface? Would bees wax help, or possibly add other issues.

slow drying of thick impasto

Question asked 2020-12-07 23:07:54 ... Most recent comment 2020-12-08 09:16:31
Drying Oils Paint Mediums

​How do you slow the drying of thick impasto oil paint (stand oil added as medium) to allow it to be worked for several days? I know pigment selection is crucial, as well as temperature/light exposure. Maybe spike oil substituted for odourless solvent, a less absorbent acrylic ground, may help. Poppy oil does help but the dried paint film is more brittle (from testing of samples). Am I asking the impossible to extend the drying time of fast driers like cobalt blue and also for it to remain flexible. I even had a box made to store the painting overnight with cotton balls soaked with clove oil, but this puts size restraints on the painting size.  I seem to solve one issue to just raise another one. Any thoughts would be appreciated.

varnishing on oil paint necessary

Question asked 2020-12-03 22:23:47 ... Most recent comment 2020-12-06 08:36:40

​I was inquiring if it is necessary to varnish oil paintings. I understand varnish can protect against UV light, dirt and abrasions, but I use very thick impasto oil paint. From what I understand it can take many years to dry. I add a stand oil to the paint, so the surface of the paint has a relatively even sheen upon drying so aesthetics is not an issue. From a conservation point of view is it best not to varnish, or varnish at about 3-6 months (probably with Gamvar). Does Frank Auerbach's work have problems as I do not think he varnished his paintings?

Cold Wax Medium as Varnish

Question asked 2020-12-04 14:43:35 ... Most recent comment 2020-12-04 15:31:03

​Can Gamblin's cold wax medium be applied to a painting as a final varnish? Will it provide adequate protection? I love the soft luster it provides. 

What to do about pinholes in oil on linen picture

Question asked 2020-12-01 08:25:56 ... Most recent comment 2020-12-01 22:10:34
Oil Paint Flexible Supports Art Conservation Topics

Question: Should I resize an oil on canvas after pinholes appeared?

I am a traditional oil painter working in San Diego. I've worked on the same picture for several years. The work is done on Claessens oil-primed Belgian linen, relatively thin and smoothe. I recently scraped the upper layers of paint off an unsatisfactory section (down to the tone ground).

Small, translucent areas and pinholes appeared (hardly surprising). 

I'm concerned the canvas could rot from direct contact with the paint. Two contacts in the industry have told me (1) the animal glue sizing penetrated the fibers, such that the risk of rot is minimal, and (2) I could apply animal glue size to the entire canvas from the reverse, but need to guard against uneven tension, warping, etc.

At present I think leaving it alone is best. I'll repaint that section and hope it doesn't rot.

Your thoughts on the matter will be appreciated.

Combining Organic and Non-Organic pigments to improve Lightfastness

Question asked 2020-11-26 08:16:25 ... Most recent comment 2020-12-01 18:21:41
Pigments Scientific Analysis Technical Art History

​Hi all,

From what I understand about pigments and from what I have read in articles from the paint coating industry, some non-Organic pigments have the ability to absorb rather than reflect UV light and without being so affected by the UV rays as most organic pigments can be.

I am thinking here of Iron Oxides, Nickel Antimony Titanium Yellow Rutile (PY53), and Chrome Antimony Titanate (PBr24) .

I believe from what I have read that the paint coating industry offer mixes of inorganic mineral pigments like this with much more chromatic organic pigments to improve lightfastness as well as opacity and reduce cost.

Am I correct in this assumption, and that if I mix say PY74 with PY53 (which is a weak tinter), or PR254 with PR101 I will improve lightfastness of the organic pigment on it's own at the expense of Chroma?

Thank you for your help,
Richard Phipps


Question asked 2020-12-01 06:04:33 ... Most recent comment 2020-12-01 06:44:58
Industrial and Non-Traditional Products

​hi I just wondering that I can use gilsonite or bitumen for house decoration and does it have a harmful point or not?

Zinc White (PW4) issues

Question asked 2020-11-23 11:50:16 ... Most recent comment 2020-11-24 07:09:57
Pigments Egg Tempera

According to recent research, zinc white (PW4) causes saponification in connection with oil paints. This means zinc white can cause long-term damage to the image. Is this also the case with zinc white and egg yolk tempera?  And how does it look like in connection with tempera grassa?

B-72 Application

Question asked 2020-11-20 09:39:59 ... Most recent comment 2020-11-22 15:08:14

Because the solvent (xylene) in my B-72 is noxious, I've been applying isolating layers in a unheated room above my studio - it's not freezing, but can get into the 40 degree F. range at times.  ​Anyone know the ambient temperature range at which one can safely apply B-72?



Question asked 2020-11-12 11:04:40 ... Most recent comment 2020-11-17 13:54:29
Paint Making

every now and then, when I am making my own oilpaint, the paint gets too stringy. I'll add some Omyalite and/or some beeswax dissilved in oil, but that seems to help only a little.

What an I doing wrong? Is it perhaps the not-premium linseed oil? Is Omyalite not the right thickener?

Thanks in advance

MSA added as oil paint medium

Question asked 2020-11-07 12:51:11 ... Most recent comment 2020-11-10 18:09:57
Oil Paint

Hello –

First, thank you MITRA for providing such a wealth of information and expertise. I have greatly improved my craft by reading your resources and forums.

My question is not addressed in your resources articles. It is: can MSA (acrylic which is not water-based) be added to oil paint with no appreciable archival concerns? The scenario I am thinking of is if the oil painter paints thin and allows the surface to be touch-dry before applying the next layer. If this is possible, I think it would help in achieving one of my goals in terms of perceived depth and luminescence, similar to Maxfield Parrish, but lasting longer.

At least one commercial provider, Lukas, offers it, albeit with dammar, and it is advocated in other art technical materials discussions.

If it is possible, what are the other process steps or materials which need to be considered?

Thank you. 

Mediums for oils

Question asked 2020-10-30 13:08:19 ... Most recent comment 2020-10-30 21:14:44

​Hello again! When I use mediums is it best to stick to one type at the beginning? We experimented with an oil butter, sand and other stuff for a cool texture. 

Appropriate Substrate Material for Mounting Pastel paper (Roll)

Question asked 2020-10-26 16:47:52 ... Most recent comment 2020-10-30 15:19:12
Rigid Supports Sizes and Adhesives Pastel

​I am looking for an appropriate mounting surface for a 4' x 6' pastel paper. If I were to mount this on an aluminum panel what is the best way to do this? Using paper mounting hinges or an adhesive of some sort? I am not sure how the aluminum surface will react to adhesive. Also should the aluminum be specified to have a desired topical finish? Thank you for your time and look forward to hearing from you. Maria Marino

OIl painting for beginners

Question asked 2020-10-30 13:01:41 ... Most recent comment 2020-10-30 12:59:00

​I am new to oil paints and jsuyt started a course which is fab but I have so may questions about how thick oyu should apply the paint, what tools make the best mark making (i.e. spatulas, or brushes) and how many layers should I start with please? Thanks

Marble dust and Oil paint

Question asked 2020-10-26 09:06:15 ... Most recent comment 2020-10-26 17:50:48
Oil Paint Paint Mediums

I want to add body to my oil paints, so I was researching about mixing marble dust with linseed oil and use that as a medium.

I don't have access to a lot of variety, fine art materials wise, so that seemed like a simple enought option.

I have a few of questions though:

1-Would it be better to just use linseed oil or would stand oil be a better alternative?
2-Could I use that mix in the initial layers, and then on the next layers use just pure paint? Or would I have to up the ammount of oil content for the next layers?

3-What ratio should I aim for? The consistency should be of pure oil paint from the tube?

Thank you!

Erasing charcoal, pigment or pastel stains

Question asked 2020-10-23 17:27:43 ... Most recent comment 2020-10-24 19:41:40
Drawing Materials Art Conservation Topics Other Pastel Studio Tools and Tips Watercolor

​A student just completed a wonderful charcoal drawing on Lanaquarelle watercolour paper. Unfortunately, she smudged it by holding it with her hands covered in charcoal dust. She tried to erase the stains, first with putty eraser, then with a normal eraser and finally with an electric eraser. The stains are still visible, as the paper is quite porous.

Do you have any suggestion on how to bring the whiteness back to the paper? Or is there any paint that looks exactly like the paper? We even thought of putting some soaked off-cuts of watercolour paper in the juicer, add some matte acrylic binder and apply it thinly over the stains!

Thank you

Primeing ACM panel

Question asked 2020-10-23 10:04:09 ... Most recent comment 2020-10-23 10:55:16
Oil Paint Rigid Supports Grounds / Priming


Would it be good practice to apply a layer of titatnium white mixed with an alkyd or cobalt dryer, on top of an acrylic polymer ("gesso"), when priming an ACM panel?

I'm a painter from Brazil and fine art supplies are hard to come by here. Ideally, I like to paint on oil-primed linen mounted on ACM panels, but linen, when you can find it here, is ridicoulosly over priced. Think like 4 times what you would pay in Europe or US.

So I'm priming my ACM panels with an acylic polymer ("acrylic gesso"). I sand it lightly and then apply up to 5 coats with a brush roller.

It is a fine surface to use, but I find that is too absorvent and the oils sink in way too much. The paint doen's flow as well and the darker colors become way too light the next day, making it impossible to judge it's values.

So a fellow painter reccomended the titatnium white with a dryer.

Would that be ok? What should be the ratio of paint to dryer?

Thank you!

Making paint with polyurethane

Question asked 2020-10-08 17:32:35 ... Most recent comment 2020-10-22 18:00:13
Alkyd Acrylic

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I am trying to make paint for art paintings on wood and paper and canvas using polyurethane (water based) Sherwin Williams as the medium/binder.

The support people at SW said nothing should be added to it by way of colorant and not  to thin it with anything, even water, as that would weaken the paint film.; (a legally safe response.)

Since the clean up directions for use said to use warm water immediately and the stuff was ‘water based’  the clerk in the store and I thought thinning with water could be done,  like the use of water in acrylic thinning where its okay if you don’t use too much.

I think I saw on some SW literature that  a wood stain could be added to the polyurethane.

I also see that the polyurethane will yellow over time , and as a matter of fact, it looks yellowish right out of the can.  I think I can live with that.

The main question is;

What are the potential or probable effects of using acrylic paint as a colorant in the polyurethane.

So far I have mixed and used some mixtures like this and also with powdered pigments, but  it has not been long enough to tell much of anything, except that they do dry pretty fast and the mixture seems stable enough over a couple of days if covered on the palette..

Kindly advise if this is a dead end, or a guess as to what bad and good things I should look out for.

Thank you.

Thanks for help with acrylic/alykd question

Question asked 2020-10-22 17:58:42 ... Most recent comment 2020-10-22 17:53:00


Please excuse the delay in responding to the very helpful answers to my original question about mixing acrylic/alkyd mediums together - dealing with the damages from Hurricane Delta is taking a lot of my time.

Thanks to Brian Baade,Matthew Kinsey and George O’Hanlon, you have provided a couple more possible strings for my bow in the hunt for the best medium for me.

organic pigments... Not lightfast?

Question asked 2020-10-21 10:18:25 ... Most recent comment 2020-10-22 14:01:07

I found this article on natural pigments about the lightfastnes of organic pigments. Time to panic?

Sennelier Egg Tempera and Acrylic Gesso panels

Question asked 2017-03-08 11:44:47 ... Most recent comment 2020-10-20 20:13:11
Egg Tempera Grounds / Priming Rigid Supports

​i have read the descriptions for how to make real ET paint (fairly easy) and real ET panels with rabbit skin glue and whiting (very laborious).

I cannot believe that lazy people like me who buy ET in tubes still have to make a panel. Panels with true gesso on are availale from few retailers and are expensive. Sennelier make passing reference to use on canvas with acrylic gesso, but their information is very poor.

Are you able to offer advice on using these tubed ET paints with commercially available wood panels with acrylic gesso, please?

Absorbency characteristics of a lead oil ground?

Question asked 2020-10-17 06:36:52 ... Most recent comment 2020-10-20 03:33:35
Grounds / Priming

Hello all,

I am currently involved in a painting project consisting of 12 identically sized HDF panels (approximately 5" x 8") each of which have been prepared with slight textural differences (linen, cotton, or a collage of linen fabric all attached to the sized substrate with rabbit skin glue) or in a few cases, acrylic sculpting gel applied to the substrate over a few light coats of acrylic gesso. All these individaul treatments - each of which follow a preconceived design - preceded the two "final" coats of white lead primer (I used Old Holland "Cremser White" from a tin, which I understand is industrial lead carbonate ground with cold-pressed linseed oil. I thinned it to flowable consistency with five parts turpentine and one part stand oil). This primer was applied and cured for one year. (Not my plan to wait that long, it's just what happened)

Now I am beginning the painting process. To reiterate, the central idea for these panels is/was to paint in oils over a traditional white lead oil ground - with this variety of textural interventions - and see what kinds of effects occur. So, I'm entirely open to fortuitous visual accidents, but at the same time I do not want my experiments to result in lack of adhesion or longevity. 

Thus, my question/conundrum: the ground does not appear to be as absorbent as I might expect. Is this normal? This week I've done a very light, thinned imprimatura in yellow ochre over all twelve and let it dry three or four days. Then I transferred my design with charcoal and reinforced it in mars black (tube oil paint) heavily diluted with turpentine. I let these underdrawings dry two or three days. They look very good, but when I used a kneaded eraser to lightly remove the charcoal lines from my transfer I can see both yellow and black on my eraser. Not good, I think. Should I have waited longer for both of these underlayers to dry? They were certainly dry to the touch. Or did I make a mistake at the get go? Should I have thinned my lead primer with more turpentine and eliminated the stand oil?

I'd appreciate your thoughts or suggestions. Of course, if I need to, I can start over; recreate some of my textures, paint in oils over an acrylic gesso ground and chalk this one up to experience, however I am curious about the benefits of painting in oils over an oil based ground.

Thanks in advance for your insights.


Ellen Trezevant

Technically sound way to do wipeout friendly ground and isolation layers

Question asked 2020-10-19 12:07:30 ... Most recent comment 2020-10-19 12:30:12
Grounds / Priming Oil Paint

I am getting very frustrated with my method but can not find the best way to fix things. I use hardboard primed with Gac100 and either Gamblin oil ground/Rublev alkyd/Wiliamsburg lead. Wait 3-4 weeks and apply a light tone of raw umber and Gamsol, wait 3 days. Start painting with unaltered tube paint, make a mistake and try to wipe it, the wipe takes off the tone and the white ground underneath is now stained. 

Ideally, I would like to have a very light tone or just white board and 2-3 painting layers on top, wiping as I go without damaging or staining what's underneath. I thought the tone was under bound but putting a richer tone was not recommended. I thought the ground was too absorbent but having a more closed off ground was not recommended either.

I'm sure I'm not the only artist trying to do this but I can't find a good example to follow. Maxwell Parrish supposedly used retouch varnish but everyone says that's a no go. Rockwell and Brad Kunkle use shellac and Richard Schmid says his lead oil ground allows him to wipe back to white but I am not able to replicate this with unaltered manufacturer grounds I tried. Please help.

Final Varnish new product help please!

Question asked 2020-10-12 16:35:05 ... Most recent comment 2020-10-17 20:50:30

​I used Old Holland Gloss Picture Varnish (made from ketone resin) on an oil painting as I was looking for a nonyellowing product.  It is too glossy.  Neither the supplier nor Old Holland can tell me if I can do a second layer with their Matte Picture Varnish without losing clarity.  Has anyone used these products?  

Mixing oils and alkyds

Question asked 2020-10-08 02:46:25 ... Most recent comment 2020-10-09 02:58:14
Alkyd Oil Paint

Kindly advise:  I work in oils, but rely heavily on alkyd paints to improve drying times.  I don’t mean alkyd mediums such as Liquin, but actual alkyd paints such as the W&N Griffin range.  According to W&N, it is acceptable to use alkyds for underpainting, and then work with regular oils over alkyds.  I take this a step further.  My underpainting is pure alkyd paint, and for the subsequent layers I mix alkyd and oil paints together.  I mix a bit of alkyd white with oil white, a bit of alkyd black with oil black.  These hybrid mixtures are then used to mix other colours which dry fairly quickly.  The upper layers of my paintings consist of pure oil paint, with some medium added to follow the fat-over-lean rule.  I should mention that I work on rigid supports, usually on a Gesso ground.  Can anyone foresee any issues with this technique?  Your advice would be appreciated!

Delamination of 1st or 2nd color layer while applying a couche

Question asked 2020-09-26 21:23:41 ... Most recent comment 2020-10-05 14:18:18

​Hello Everyone,

I find that when I need to apply a couch to paint into to merge my layers and match my value, sometimes my previous color layer starts wiping off, destroying hours and hours of previous work. This never used to happen when I was more reckless in my early years. But now I paint solvent free and use as little medium as possible. For context I paint on museum quality gesso board (acrylic ground). I use lead white and typically do my underpaintings with a mars color and white or old Holland raw umber. Sometimes I seal my drawing with acrylic matte medium, sometimes just a light layer of raw umber and lead white. What I can't seem to figure out is if my under layers are underbound or if the couche I'm applying is the cause of delamination. It was my belief that a couch would not only make each new layer fatter but INCREASE adhesion and not the opposite. I typically use oleogel or walnut gel as a medium. Does anyone know what could be causing this issue?


Question asked 2020-09-29 09:44:55 ... Most recent comment 2020-09-29 18:52:44
Health and Safety

​What are the health issues with being pregnate or having an infant in art schools or home studio? 

Golden Acrylic paint: pigment concentration

Question asked 2020-09-15 05:57:19 ... Most recent comment 2020-09-17 10:38:34
Acrylic Pigments

​Hi to the MITRA team,

I have questions about the pigment concentration (pigment load) of the Golden Paint line.

There are four viscosities in Golden paints (heavy body, soft, fluid and high flow acrylic) and I would like to know if there are differences in the pigment concentration between the Golden acrylic range.

I understand that the polymer binder used is the key to the consistency of the paint, but strictly speaking about the pigment concentration, what is the most loaded paint?

It is said in the description of the Golden paints that they contain no fillers or extenders, does it mean that the paint is fully pigmented as in some high quality oil paints?

If I want to extend acrylic paint while maintaining the most of the saturation, what should be the optimal dilution factor?

Thanks in advance,


Use of eggwhite in oiling out mixture

Question asked 2020-08-29 09:19:42 ... Most recent comment 2020-08-30 00:24:38
Drying Oils

​Dear MITRA I have been reading about using a mixture of sun thickened linseed oil and egg white to oil out the painting surface at least initially (before the first layer; I'm not sure if my source recommends it between subsequent layers or not) and am wondering if this presents any problems as regards the stability of the paint film long term? 

Restoring color to a shellacked totem pole

Question asked 2020-08-13 13:55:17 ... Most recent comment 2020-08-28 08:28:30
Acrylic Alkyd Art Conservation Topics Dyes Grounds / Priming Industrial and Non-Traditional Products Oil Paint Other Paint Additives Paint Mediums Pigments Solvents and Thinners Varnishes

​I have a custom made totem pole that is over 20 years old.  It has been shellacked a few times in an effort to preserve the wood. Although this seemed to work, the colors have darkened and disappeared.  I am trying to restore the original colors and need advice as to what type of paint products to use. Would appreciate any advice. 

Russian Sauce vs Soft Pastels vs Watercolour

Question asked 2020-08-24 19:56:05 ... Most recent comment 2020-08-25 14:56:08
Pastel Watercolor Drawing Materials Ink

I’ve been curious about Russian sauce and its use in drawing. I see that some artists enjoy applying washes of this medium on their drawings. Is there any advantage of Russian Sauce when compared to washes made with powdered soft pastels or watercolour? And what’s the best brand of Russian Sauce? I only seem to find Yarka and no info about lightfastness? Thank you

ratio of Regalrez 1094 resin to solvent

Question asked 2020-08-21 21:34:31 ... Most recent comment 2020-08-22 20:21:45

​I have Regalrez 1094 in resin form, and i need to know the proper ratio of resin to solvent. I would like to limit the size of the resulting mixture to about 2 oz. per session. I do have Tinuvin 292 to add to the resultant mix.

Matting Agent

Question asked 2020-01-06 11:15:30 ... Most recent comment 2020-08-09 12:34:56
Paint Additives


Do you know specifically what substance(s) are added as matting agents to matte varnishes and mediums?   

Thanks, Koo

Golden fluid Tg

Question asked 2020-07-05 06:36:53 ... Most recent comment 2020-08-07 16:22:07
Art Conservation Topics Acrylic

Hello forum,

does anyone know what is the glass transition temperature of the Golden fluid acrylics?

I NEED HELP IDENTIFYING A "Dutch Oil Landscape Painted on Copper"

Question asked 2020-08-07 10:59:43 ... Most recent comment 2020-08-07 11:48:09

​Hello, I am hoping someone can give me some tips or adivce on the best way to identify the artist and name of a painting. My friend was given a painting through probate. The issue is that certificate on the back is missing (you can the square the patch on the back of the where the certifcate would be. The painting has no artist signature. 

All the info we have have is that it is a "Dutch oil landscape" and it is painted on copper.  I belive it is an orginal becuse it purchased 30 or so years ago from an auction house in New Orleans. However, the auction house has changed ownership 4-5 times since then and they do not have the records from 1995.

Please see the links below for pictures of the painting. Any help would be much apperciated!

acrylic retarder

Question asked 2020-08-06 02:57:55 ... Most recent comment 2020-08-06 10:40:48
Paint Mediums Acrylic


Hello Mitra, I have a bottle of propylene glycol and I am going to use it as a drying retardant.

I have read and tried different brands of retardants and each of them gives different ratios.

I assume that each brand uses different products and different dilutions.

-How much propylene glycol is safe to form a good paint film?

-Is there a more effective product than propylene glycol apart from using golden open gel medium?


Oil paint failure

Question asked 2020-08-01 14:52:48 ... Most recent comment 2020-08-02 16:32:00
Art Conservation Topics Grounds / Priming Oil Paint

Hi all,

I've just come back from Mallorca, Spain visiting my parents in law. I noticed one of the paintings they had in their house had quite substantial cracking (mostly in light areas.. zinc white?) and paint adhesion failure.

The painting was dated with the signature to 1944 and received a lot of indirect (or direct) sunlight and high temperatures.

I just thought it was interesting how badly the paint film was doing. I'm not sure if the canvas was primed correctly either?



Question asked 2020-07-15 05:15:01 ... Most recent comment 2020-07-17 20:16:38


Hello Mitra, I have been experimenting with  AM (Kremer) alkyd resin not only to make paint but to make a medium and putty.

-Using the raw resin the paint becomes unusable in a matter of minutes.

Only when the resin is diluted in approximately 20% resin 80% normal linseed oil does the paint have desirable properties.

The same thing happens when I make a medium that becomes sticky in no time if I don't add oil.

My questions are:

1-Is it normal for this to happen?

2-When manufacturers name a line of paints as alkyd, is it possible that they only contain a very small fraction of resin?

I love the work that you are doing.

Thank you.

Acrylic gesso's opaque pigments

Question asked 2020-06-27 01:42:06 ... Most recent comment 2020-07-14 15:27:33
Acrylic Grounds / Priming

​It seems logical to suppose that the only opaque white used in the art market's acrylic gesso is titanium white, with no zinc white.  Is this a safe presumption?  I'm looking to reassure myself that there's nothing in these grounds for absorbed oils to react with.


how to chose glass railing spigot?

Question asked 2020-07-13 06:38:25 ... Most recent comment 2020-07-13 14:30:36
Matting, Framing, and Glazing

Hi all,

I don't know if this question should be show in this cagegories if I am wrong, I am sorry.

My question is about the glazing and glass, about the glass railing spigot? As you known, there are many different kinds spigots, if build a new glass railing, chose the stainlesss steel or the brass one? which one is better? who can tell me? thanks very much


What Size for Casein Ground on Rigid Support

Question asked 2020-07-03 08:39:29 ... Most recent comment 2020-07-05 13:34:05
Sizes and Adhesives Grounds / Priming


New to this I'm sorry if this has been asked before. Sometimes I use casein paint as a ground on rigid supports like hardboard to paint with oil colours on top. Also under it I tend to use rabbit skin glue as a size (or a transparent acrylic 'gesso' which I have found it to be a great sealer) Just wondering if the size layer is necessary...or if just few coats of skim milk might be enough to act as a size?

How are professional poster color paints made?

Question asked 2020-06-26 20:02:27 ... Most recent comment 2020-07-03 15:54:47
Paint Making Gouache

I read: 

And contacted a few manufacturers, but they gave me very little info, other than that they have "extender pigment" and other additives. So not just gum arabic with pigment. 

I'm wondering if there is a poster color medium out there that I can just add a pigment dispersion to?  

I was recommended to come here from reddit, so first post! 


Acrylic primer cleaning

Question asked 2020-06-23 16:50:42 ... Most recent comment 2020-06-26 17:33:09
Oil Paint Acrylic Grounds / Priming

​If acrylic is more vunerable to the solvents used to clean oil paint and remove varnish.  How should one guard against future damage on an oil painting applied over an acrylic primer?

Is it enough to cover the entire acrylic surface with oil paint?

What if an artist wishes to have gaps in the brush work. leaving blank white acrylic primer spaces?  Is this safe?  Should they reprime with a white oil paint first?


Oil paint directly on top of PVA size

Question asked 2020-06-24 16:35:57 ... Most recent comment 2020-06-25 22:24:23
Oil Paint

​A well know painter recently stated he uses Gamblin PVA size to seal his drawing on acid free 270 gsm smooth paper. When dry, he adheres the paper to a sealed rigid substrate. Then he paints directly over his drawing with oil paint. Is there any known problem with this method and does PVA seal the paper from the oils? Can oil paint adhere well to the PVA? Would it be better to seal the drawing with casein based fixative instead of PVA? 

Hands on drawing paper

Question asked 2020-06-24 15:42:37 ... Most recent comment 2020-06-25 18:43:39
Drawing Materials Handling and Transportation Pencil Art Conservation Topics Flexible Supports

​Hello dear people from Mitra!

I have a question about paper safety while drawing. 

I am really trying my best to put some paper beneath my arm(hand) while i am drawing so i dont put my bare hand on drawing paper.

But sometimes when i want to  put it aside, i touch it with my bare hands.  And sometimes my hands get a bit sweaty, but this lasts only few seconds...

The papers i use are thicker watercolor papers and are Acid Free, but i wanted to ask will these few direct contacts with paper and with barely sweaty hands cause a big problem? 

Thank you

Hansa yellow light (PY3) lightfastness in mixtures

Question asked 2020-06-23 01:28:13 ... Most recent comment 2020-06-25 06:52:32

​Dear MITRA people. I have a large amount of Gamblin PY3 oil-based etching ink but have been reading recently that the lightfastness of this pigment is questionable. On further reading about it in the Just Paint newsletter from Golden in an article from 2018 about changes to their yellow range in acrylics, it seems that this poor rating is based on its behaviour as a tint when mixed with titanium white and it was suggested that there might be some sort of adverse synergy going on between them in acrylics. 

This article however also mentioned that it was performing well in oils (and strangely, watercolours). I do know lots of oil painters who feel it should be avoided, What is your opinion of the lightfastness of this pigment in oils (whether paint or printmaking ink) and would it be fair to imagine that if I use it in mixtures that don't include a white, it should be reasonably reliable? 

Preservation of Acrylic on Watercolor Paper

Question asked 2020-06-11 17:18:01 ... Most recent comment 2020-06-23 19:49:18
Acrylic Art Conservation Topics Varnishes

Should acrylic on watercolor paper be framed under glass? If so, why? The paint application was very watery, like watercolor paint. I used Golden Fluid acrylics. Or, does a varnish suffice? Thank you.

How Archival Are Acrylic Paintings?

Question asked 2020-06-19 20:20:42 ... Most recent comment 2020-06-23 19:46:47
Acrylic Art Conservation Topics

​I have read claims by amateur artists that because acrylic paints are "plastic" they will last forever and never crack or delaminate. I quite enjoy painting with acrylics and am curious what we actually know from experience or research, or can infer about the longevity of acrylic paintings. There are so many ways to use this versatile medium that I also wonder whether how you use it affects its archival properties. Thanks for your thoughts.

modern alternative to collagen for a flexible gesso?

Question asked 2020-06-19 16:28:48 ... Most recent comment 2020-06-21 20:44:47
Grounds / Priming Animal Glue


I am happy to have found this science-oriented forum (through koo schadler's site), and I have a few questions to ask.

I did silverpoint some years ago on traditional gesso (rabbit skin glue and whiting).  I am getting ready to do it again.

I observed then, that while traditional gesso is pretty hard, it is brittle and requires that rigid support.  I just asked natural pigments how "silverpoint on prepared paper" cited in museums catalogues of renaissance silverpoint drawings even worked, without flaking off the page.

Natural pigments replied that paper usually meant vellum, which was a little stiffer than what I was thinking of.  They also replied that these drawings were mounted and preserved from a very early year, and not subject to that much bending and flexing.

it's 2020.  I'm wondering if there are flexible, and archival, substitutes, that would make a more flexible gesso less likely to crack?

I am also already looking into alternatives to whiting, which is only a 3-4 on the mohs scale, and just barely hard enough to scratch annealed silver.  I'm thinking, 1200 grit aluminum oxide polishing rouge, 1200 grit silicon carbide (for goldpoint-- it's grey), or 400 mesh silica flour, all of which are much harder than ground whiting.  I don't see any reason they won't work! (but if there is a reason please tell me :) )  One is budget, but I live in hawaii now so the price difference between whiting and alumina is much diminished after shipping.  I miss just walking to a pottery store and paying $15 for a big bag of whiting...
Except crystal structure IF I was planning to use gold leaf, then you need a planar silicate that will lie flat so it is burnishable.  but that's what bole is for.  

commercial alkyd primers?

Question asked 2020-06-19 16:38:55 ... Most recent comment 2020-06-19 17:17:40

In preparing my own canvases, is there a commercial alkyd primer you would recommend?  (e.g., home depot, sherwin williams).

To add to the confusion, some commercial alkyd paints have added polyurethane, or even added silicone (considered the more premium choice).  Unsure how those would affect linseed and safflower oil layers of traditional paint on top.

Oil paint on "semi-primed" cotton/linen

Question asked 2020-06-19 10:01:06 ... Most recent comment 2020-06-19 16:15:24
Oil Paint Sizes and Adhesives

​Francis Bacon painted on the back of a primed surface. Are there any concerns with this approach given that one side is properly primed PVA,oil ground etc.

Many thanks

Pen for signing oil paintings?

Question asked 2020-06-16 15:10:24 ... Most recent comment 2020-06-19 00:12:07
Oil Paint Varnishes

​A woman I know wants to sign her oil painting using a pen/marker that is compatible. Obviously, acrylic-based markers would be bad! (Acrylic doesn't adhere well to oil paint film.) I’m wondering though, about enamel-based pens. Or Pebeo has an oil pen that uses a synthetic mineral oil as the base.

Byeond simple good adhesion, the other concern is the pen/marker holding up to varnishing and later removal of said varnish.

hardware store linseed oil

Question asked 2020-06-03 18:22:50 ... Most recent comment 2020-06-16 17:31:25
Drying Oils

​One of my students informed me that he is painting using boiled linseed oil from the hardware store. I advised against it. Did I give him the right advice and what is the problem if any with using generic non artist grade linseed oil to paint with?

Silverfish eating my egg tempera painting

Question asked 2020-06-14 15:46:22 ... Most recent comment 2020-06-15 23:35:25
Egg Tempera

​anyone experiencing e with silverfish eating tempera paint from the painting?


Reducing Zinc in Whites by Mixing Different Types

Question asked 2020-06-07 10:10:11 ... Most recent comment 2020-06-10 02:20:20
Oil Paint

I am aware that it is possible that Zinc Oxide can cause delamination and cracking in oil paint layers.  Unless there is some new information I missed, apparently there is no known safe amount of Zinc Oxide in the paint that will stop this for sure. I have read that less Zinc content is logically better if you do want to continue to use Zinc Oxide containing oil paint. I would appreciate hearing the latest from any of the moderators here who might want to comment on the following. 

I have a large volume of Titanium White oil paint that has a Zinc Oxide content of 15% or less. I am not really wanting to throw it all away. I have decided to use that what only on rigid supports, but would also like to reduce the ratio of Zinc Oxide in it, if I can. Would it be worthwhile to mix existing Titanium / Zinc whites that have higher ratios of Zinc Oxide in them such as a known 15% maximum with Zinc free white paints and are there any lead free pigments such as PW5 / Lithopone or PW21 / Barium Sulfate that might be more apt to help reduce delamination and / or cracking? 

On the same topic of the possible problems with Zinc, would it be advisable to avoid using acrylic underpainting layers when using Zinc containing oil whites? How about using oil grounds vs acrylic dispersion grounds with the same whites? And lastly, does the thickness of the layer containing the Zinc Oxide have any impact on the potential for cracking or delamination?

Thanks in advance for your input.

What wood is suitable for painting?

Question asked 2020-06-08 15:11:13 ... Most recent comment 2020-06-09 10:19:27
Rigid Supports

​Hello Mitra,

I know the old masters used  solid poplar and oak wood panels that were dried heavily in order to avoid warping and having the acids rise to the surface.  Obviously they also sealed them in order to have extra layers of protection.

Now a days with ovens that dry the wood, and things like plywood and mdf like  wood,  im curious to know if we have to worry about the acids rising to the surface and about the warping? Technically plywood warps less and mdf if sealed doesnt absorb moisture and shouldnt warp.  I dont know about the acids in the mdf and if they are problem.

Are plywood and mdf panels suitable for painting? Should artists just stick to solid wood? Are MDF boards and plywoods even archival? 


Synthetic Papers for Painting Substrates

Question asked 2020-05-29 15:25:31 ... Most recent comment 2020-06-03 17:27:22
Flexible Supports Grounds / Priming Oil Paint Matting, Framing, and Glazing Rigid Supports Sizes and Adhesives

Hi all,

My surface of choice is an ACM panel (lightly sanded and with an acrylic clear gesso applied). However they can be a bit expensive for more experimental or practice works. Or when a painting goes wrong!

So I have been looking into synthetic papers and after looking at a selection of samples I tried a small sheet of PICOFILM from SIHL. It worked so well I ordered some larger sheets to do a painting on, which came out really well. It's basically white PET-G with a very matt primer which gives the the very slightly coarse feel of paper.

Here are the details of the surface from their technical sheets:

PICOFILM P-125 M2 matt

Synthetic matt paper. Ideal for waterproof and tear-resistant loop-locks, hang tags, weatherproof hiking maps, race numbers, menus, hard-wearing handbooks, booklets and brochures. 

PICOFILM P-125 M2 is a white polyester film coated both sides with a matt primer. It is weather-resistant, chemical-resistant, temperature-resistant and dimensionally stable. It can be cut, punched, perforated and drilled without issue. It’s also suitable for hot foil stamping and laser cutting. 

The high-quality coated film surfaces offer optimized feed properties and printing results. The slightly coarse surface, which is specially developed for laser printing, has an anti-static effect and prevents double-feeding. Suitable for monochrome and fullcolour laser printing, and for UV flexo and conventional offset pre-printing with oxidative drying inks. With fast ink drying, ideal ink adhesion and toner fusing. Can be stamped easily and lettered manually. 

High tear resistance
Excellent ink adhesion and toner fusing

The surface is very matt, even more than a white polyester coil coated matt ACM panel. It has a slightly rough feeling like paper or ultra fine sandpaper. The primer can be easily scratched off with a fingernail, but otherwise is a perfectly level and even surface (more than can be achieved using acrylic paint)

I applied two coats of clear gesso and it didn't buckle or warp as even heavyweight paper does. When I tested water paints and oil paints on an untreated surface I saw some absorbtion but absolutely no warping or cockling.

The oil paints developed the familiar oil ring of an absorbent surface after some hours and the paints did dry quicker (but still took several days or longer to dry).

Adhering the paper to a board is a bit tricky because both the surfaces of paper and ACM panel are plastic I've found Golden Acrylic Gel and PVA glue do not seem to dry (even though there seems a bond). They still appear wet when pulled apart after several days.

I'm currently testing out some Pressure Sensitive Adhesives (spray, tape and pot based) but I am seeing some distortion of the thin paper (bubbling underneath) from the glues - possibly from the solvents, so going to try leaving them to dry more thoroughly before bonding. There are also thicker grades of PICOFILM available, but don't know how much that would help.

I tested out sticking the PICOFILM paper to a paper mountboard from Daler Rowney with PVA glue and the bond was so strong then when I tried to remove the PICOFILM it was pulling off layers of the mountboard until the PICOFILM inself ripped when I used great force.

So, my concerns are:

If the primer is mechanically stable enough to be used with oil paints without some additional gesso or primer.

Is the primer going to react negatively with the oil paint.

Can I adhere it to a rigid surface without visible bubbles from the glue appearing and getting it to form a suitable bond.

I like the surface and it works out very cheap compared to thick normal papers (which still need stretching), or canvas/linen.

I have been in touch with SIHL who produce the paper and they've not heard of anyone using it with oil paints before. They are keen to know my experiences with using it and have sent me more samples.

I wondered if you had any thoughts, or any experience with artwork on these new synthetic substrates?

Thank you for your help,

Nontraditional use of egg tempura

Question asked 2020-04-03 12:26:51 ... Most recent comment 2020-05-18 01:07:43
Egg Tempera

​I have a few questions. I'm a painter/printmaker and have enjoyed making very juicy, loose oil paintings and monotypes for a long time. I've always been captivated by the color quality of egg tempura. I bought a set of Sennelier egg tempura tubes and egg tempura medium. I'm thoroughly enjoying painting loose and relatively thick layers, which I realize is totally nontraditional for this medium. Do you have any advice how to best protect my finished pieces? What are the disadvanages to painting thick layers instead of multiple thin layers? What are the disadvantages of not applying any protective layer over the egg tempura paint? Basically I just want to keep experimenting in my own juciy, expressive way and be able to protect the paintings.

Methylcellulose/oil emulsion paint

Question asked 2020-05-10 08:49:02 ... Most recent comment 2020-05-10 13:45:55
Oil Paint Industrial and Non-Traditional Products

I've come across recipes that claim methylcellulose gel (made from powdered MC mixed with water and allowed to gel) can be used as an emulsifier, much like egg yolk, and added to oil paints to make them faster-drying and (up to a point) water-miscible. Is this as archivally-sound as using egg yolk? Are there any special precautions that need to be taken?​

Titanium dioxide permanence.

Question asked 2020-05-04 02:27:28 ... Most recent comment 2020-05-08 22:38:17
Pigments Oil Paint Art Conservation Topics

​Considering that titanium (oil paint) forms a weaker film than lead, and it's been in use for around 100 years, is anyone aware of any conservation issues arising from its use yet?

Also, I'm interested in mitigating the weakness of titanium with the addition of lead. Does anyone know if there have been any stress tests done with different proportions of lead mixed with titaniun?

Ron Francis

Acrylic Primer with Sand OK under oil paint?

Question asked 2020-05-01 04:18:49 ... Most recent comment 2020-05-01 19:43:03

​Dear MITRA people

I have some acrylic primed artist grade polyester canvas that I find objectionable to use because it has very little texture or tooth (unlike another brand I tried that was lovely to use). The surface is rather slick. I have tried experimenting with home made grounds made of acrylic primer plus marble dust or calcite as well as acrylic primer with pumice but the first 2 gave too little tooth and the last one (because we can't get ultra fine pumice in Australia) was far too coarse. I recently found some Liquitex brand "Natural Sand" acrylic gel, and put a thin coat of it over the original priming on the polyester canvas. It definitely gave a good degree of tooth. Is it relatively sound to paint over this in oils? I will be adhering the canvas to a board first as I always prefer a rigid support. 

Egg Tempera Cracking/Crazing

Question asked 2020-04-28 17:41:55 ... Most recent comment 2020-04-30 18:37:45
Egg Tempera

Background: I have a panel with many layers of egg tempera on it, and I put a "nourishing coat" over some areas. After it dried the surface developed a large number of tiny pits and cracks. My emulsion, which I used for the nourishing coat, is 1:1 egg yolk and white wine. The nourishing coat was ​straight emulsion, and I should have diluted it with more wine (1:2 egg yolk to wine). I assume that the yolk created too much surface tension and pulled at the paint layers, creating the pits and cracks.

Question: is there any way that I can fix this problem? I am many months into this painting and it would be devastating to lose it at this point.

My Current Actions: I tried painting a diluted nourishing coat over the affected areas to no avail. I then tried brushing straight wine over the affected areas, many, many layers, which seemed to work. I assume because I was breaking some of the surface tension of the rich emulsion (1:1 wine to yolk). Most of the pits and cracks closed up, but then I let it dry completely and they opened slightly again. The end result is better than what it was, but it still isn't where I want it to be.


Mixing a Drying Oil with an Alkyd Medium

Question asked 2020-03-30 09:54:04 ... Most recent comment 2020-04-17 20:57:01
Alkyd Drying Oils Oil Paint Paint Additives Paint Mediums

I have seen where some manufacturers do give the OK to mixing OMS with their Alkyd Mediums. What if one wished to add a Drying Oil such as Linseed or Walnut oil mixed with an Alkyd Medium to moderate the drying time? Of course, being sure to follow Fat over Lean rules by adding the same amount or slightly more drying oil in the mixture to each subsequent layer.

  • If it is OK to do so, is there a safe maximum amount of drying oil that could be added to most alkyd mediums?
  • For the moderators who also work for a specific brand of art materials, what would be a safe amount of drying oil to add to your various Alkyd mediums?
  • Would it be best to stick to a specific ratio mixture of the drying oil with a chosen Alkyd medium to be used throughout the painting, or should slightly more oil be added to the mixture for each new layer, not exceeding any recommended maximum drying oil to Alkyd ratio?
  • If the answer is no to mixing drying oils with Alkyd mediums, what is the reason for not doing so?

I am looking for a general guideline if that is possible to give a maximum ratio of oil to Alkyd medium that would generally be safe to use with most Alkyd mediums, even if it was a very low percentage. It doesn't take much Walnut oil for example to slow the drying rate quite a bit with some paints. I realize that all Alkyd mediums are not the same and that some makers might recommend not adding any drying oil to their Alkyd mediums, so it should not be done with those products. Additionally, a maximum recommended amount of medium for one brand may not work for another brand that doesn't give any ratio recommendations, which means an all-inclusive answer may be impossible to provide, but I was very interested in seeing what you folks had to say about this. 

Linen to panel adhesive

Question asked 2020-03-30 14:05:38 ... Most recent comment 2020-03-30 20:33:37
Oil Paint
A collector sent me a photo of a painting he purchased from me that had huge ripples and sagging. It was a commercial linen canvas on stretcher bars. I will fix it for him and intend to glue it on a hard panel; what is the best adhesive to use to adhere to a composite material panel?

How to make oil paint very matte

Question asked 2020-03-22 00:41:05 ... Most recent comment 2020-03-26 20:14:53
Oil Paint


I'd like to have passages in an oil painting that resemble poster paints in their very matte sheen. 

Can you recommend some ways to make oil paint extra matte? 

I've had a little luck with additional OMS/ Turps, absorbing oil from cardboard, and the additon of cold wax, but wondered if there were other/ strong 'matting agents' for oil paint. I think Gamblin makes a Matte Oil paint (how?) I have yet to find in stores...



Source for lead primer

Question asked 2020-03-11 05:16:02 ... Most recent comment 2020-03-21 22:14:11
Grounds / Priming

​Can anyone tell me a source for lead primer made without marble dust?

resuming work on older oil paintings

Question asked 2020-03-11 01:57:35 ... Most recent comment 2020-03-17 20:16:10
Oil Paint

​Dear MITRA,

I have searched the MITRA forum and resources, and while I have read similar questions to mine, I am not locating an answer to my exact inquiry.

I am about to resume work on a large format oil on linen diptych after I had to set them aside for a few years. I recently received funding to complete the full project for an upcoming solo exhibition, so I look forward to completing these initial works. I want to use the soundest methods possible to finish these canvases, and would like to know if my approach sounds like the best route to take.

I am using oil paints made with walnut oil, and initially used a solvent-based alkyd medium cut 50/50 with OMS for my underpainting, then a walnut/alkyd medium with increasingly less OMS for subsequent fatter layers. I never adulterate more than 20% as I alter the fat-to-lean ratio. On large parts of each canvas, the underpainting and canvas tooth are still visible, while other areas are comprised of a second or third layer as I had developed them to near completion.

Here is my suggested approach to complete the works, along with my questions about each potential step:

1. Cleaning – I plan to give both of the canvases a gentle rub with OMS to get rid of any potential dirt or fingerprints, etc, before resuming painting.

2. Sanding? –

(a) do I need to gently abrade the areas where I got as far as a second or third layer to break the seal of the paint and insure best adhesion? Or only sand where any fatter third layers look glossy? I presume that I wouldn't need to sand the underpainting areas that still feature good canvas tooth.

(b) If sanding is recommended, since I don't want to alter my composition (so pentimenti isn't a concern), would I only need to break/scuff the surface, rather than sanding down to the underpainting? Would wet sanding with a little OMS or distilled water be advised for safety? (I know to wear an appropriate mask and dispose of the pigment dust responsibly, etc.)

(c) I also wondered if I'd only need to sand where the final highlight and darkest shadow layers are going, but that sounds potentially more complicated or confusing and would limit my method of execution.

3. Limiting layers – for best adhesion, in this case should I limit myself to a certain number of paint layers wherever possible? I typically use an indirect painting method to create a fairly naturalistic end result by employing glazes on top of a wet-in-wet or wet-on-dry base. As I recall, limiting yourself to three layers including the underpainting when possible is a good practice for longevity anyway…? The number of layers I would need to employ would also be affected by how much (if any) sanding you would recommend, because I will essentially have to redo anything I sand.

I welcome your input on the best way to proceed. While I know that resuming work on canvases whose layers are this closed off isn't necessarily the best case scenario, starting over does not appeal to me from the standpoints of both time and expense. I frequently see Old Master examples wherein the artist spent years completing the works or resumed painting after a few years, so I suppose there are worse studio practices. 

Thank you so much for your time and expertise!

Removing mold from pastel sticks

Question asked 2020-03-13 08:29:10 ... Most recent comment 2020-03-14 12:28:08

How do I systematically remove/treat mold or mildew on my affected pastel sticks in a relatively safe manner in my studio  (in humid Louisiana and try to prevent its return? 

Mold/mildew on pastel sticks

Question asked 2020-03-11 22:03:19 ... Most recent comment 2020-03-11 23:52:49

I recently found numerous white small tuffs of mildew or mold growing on my very dark pastels (dark brown/black/blue), with two pastel companies' brands being most affected. My studio is in the gulf South, an area of high humidity and I run the air conditioner when It is warm and I am at the studio (not all the time). I need to figure out why it seems that only the darks are getting this growth it the possibly the preservative used, why mostly these two companies, why just the darkest darks, and most importantly, how do I systematically tackle the systematic cleaning of the pastels  in a relatively safe manner. I can send images, if that is possible.

number of pigments in an admixture?

Question asked 2020-03-11 03:33:04 ... Most recent comment 2020-03-11 17:19:29
Oil Paint Pigments

​Dear MITRA,

I've always favored a fairly limited oil palette, preferring to create my own admixtures rather than buy every tube of brown, green, or flesh tint. Recently I have expanded my palette to include some natural earth colors as I have begun to focus on using leaner *pigments* under fatter ones in addition to following the fat-over-lean rule regarding the amount of oil medium added.

Is there a limit to how many pigments are a preferable maximum in any given admixture? Does it complicate the chemistry too much to blend several pigments to get just the right color? Is there any rule about mixing natural pigments with synthetic ones?

Many thanks for your help!

Using Pigment Markers on Acrylic Gesso

Question asked 2020-03-11 10:04:42 ... Most recent comment 2020-03-11 16:43:00
Acrylic Art Conservation Topics Grounds / Priming Solvents and Thinners Varnishes

Hi all,

I would like to explore using W&N Pigment Markers which seem to use a good selection of commonly used ATSM I/II pigments but are available in a marker form. I already have a few of their water colour markers which I like, but there are many more colour choices in their Pigment Marker range.

However they are ethanol based and I understand that alcohol/ethanol would act as a solvent on acrylic gesso? I know they can be used on Yupo and other alcohol resistant plastics, but I am looking to add clear Gesso which contains silicia make a more toothy suface. A non-absorbant, more pastel ground like surface.

Considering that with the markers I would be making rubbing motions I'm not sure what I could put over the Gesso to protect it from the alcohol. Are there any varnishes that are not soluable in alcohol but will resist a rubbing motion?

The only thing I could think of was a layer of water based polyurethane (but I am concerned about yellowing).

Any ideas or suggestions?


Lead primers

Question asked 2020-03-11 05:12:39 ... Most recent comment 2020-03-11 05:07:00
Grounds / Priming

​Can anyone point me to a source for a lead primer made without marble dust (calcium carbonate), either a maker or a seller?

resuming work on older oil paintings

Question asked 2020-03-11 00:53:41 ... Most recent comment 2020-03-11 02:00:40

​Dear MITRA, 

I have looked through other posts and while similar questions have been asked, I do not see my exact question.

I am about to resume work on a large format oil on linen diptych after I had to set the works aside for a few years. I started them in 2013, and last worked on them in 2015. Now I have funding to complete the project for an upcoming solo show, and want to resume work using the soundest methods possible. I don't want to cPlease let me know if 

1. Cleaning -- with OMS then let dry

Glue emulsion

Question asked 2020-02-21 22:01:21 ... Most recent comment 2020-03-10 16:57:51
Egg Tempera Oil Paint

​I am interested in experimenting with glue emulsion and oil paints.  My understanding of what the emulsion paint is capable of doing may not necessarily be in line with what is sound painting practices.

 I have a recipe from Patrick Betadier's technique mixte I will probably follow to make the emulsion.  The ingredients are methil cellulose, linseed and stand oil, turps and dammar varnish and water.

My question is more in terms of using the emulsion within the oil layers and whether that's possible, as the emulsion paint would essentially be neutral in the system of fat/lean.

So the painting would be built following fat over lean in oil, however the emulsion + pigment paint would be introduced and sandwitched between layers of oils.  My interest would be more limited to painting final details, where I would apply a thin colored oil glaze and work into it with the emulsion paint.

I am wondering if glue emulsions are indeed fat/lean neutral and if now, what are their limitations.

Final Varnish on an Encaustic

Question asked 2016-11-10 19:00:28 ... Most recent comment 2020-03-09 13:33:15
Encaustic Varnishes
What archivally sound permanent or removable protective finishes if any have been used/recommended for encaustic works that provide a more durable finish on top of the wax surface to help protect it from pollutants and contact damage? Under the recommendation of Golden products I have been using their removable acrylic varnish for about a year now with excellent results but would like to look at other options.

Micronized Zinc Oxide

Question asked 2020-03-07 10:39:09 ... Most recent comment 2020-03-09 11:21:09
Art Conservation Topics Oil Paint Pigments Scientific Analysis Varnishes

​Hi all,

I've been reading about how micronized (or nano-particle sized) Zinc Oxide is used in Suncream to protect from UV light. As I understand it the very small size particles also make the zinc oxide more transparent.

Would this form of Zinc oxide used in a varnish (perhaps as a matting agent) help with UV protection? Would it break down being metal based?

Also, I wonder if this form of Zinc oxide added to oil paint would help contribute metal ions to the oil firms, but without the brittleness it can cause?


A bit of rust in a pen for ink

Question asked 2020-02-26 06:29:36 ... Most recent comment 2020-03-05 11:19:35
Ink Pen

​Hello dear people from Mitra.

Recently i began a ink drawing that i am really happy with, but last night i realised that my pen for ink had started to rust a bit...

The reason i didnt realise this before was because the pen was working great, and it was not clearly visible. I realised this when i had put it in destiled water and it was a bit yellowish, then i looked inside the pen and saw a little bits of rust on it...

I really care for my materials and especcialy my art, but i guess that this stuff happens.


I hope that artwork will remain as it is, but i wanted to ask to be sure? 

Thank you 

Kind regards

Marko K

Custom Table Pads

Question asked 2020-02-27 03:51:47 ... Most recent comment 2020-02-27 19:44:23
Other Drawing Materials

What kind of tables you are using for drawing, do u have any requirment of of <a href="">table pads</a> ?​

Fixative or varnish for oil & wax based pencils on paper

Question asked 2020-02-07 08:24:30 ... Most recent comment 2020-02-27 19:41:16
Pencil Varnishes

​Hi! I'm trying to find a suitable fixative to protect my drawings made with oil- and wax-based colour pencil on 300gsm Arches hot pressed watercolour paper. I only need to protect against accidental smudging and UV protection is not my concern (I only use ASTM 6901 grade pencils).

I've tried a Schmincke universal fixative so far (I live in Germany so that was a natural choice) and it gives good smudge protection and almost no colour change. However it lists "polyvinyl resin" as its main binder which is ambiguous, and Schmincke have officially declined to disclose any further details on the type of resin they use. From what the industry uses, I assume it must be polyvinyl acetate which is known to slowly disintegrate, releasing acetic acid. Assuming that fixative indeed uses polyvinyl acetate, would you consider it archival enough to be used with paper and colour pencils?

My second question is: what's the best recommended smudge protection fixative/varnish for oil/wax-based coloured pencil works on paper? I did a fair amount of googling but resources related to coloured pencils protection are virtually nonexistent (also no vendor in Europe, to my best knowledge, market any varnishes/fixatives as specifically suitable for coloured pencils).

Thank you very much for any assistance you'd be able to provide with this topic!

Technical queries (isolation varnish + final varnish) in the Mixed Technique (ET + oil)

Question asked 2020-02-21 14:07:42 ... Most recent comment 2020-02-21 17:53:00
Varnishes Egg Tempera


thanks a lot for all your comments and suggestions. 

I know that it is not recommended to varnish or coat an egg tempera painting. In my case I use ET for the underpainting because it allows me a very precise drawing and it dries really fast. The problems come when I add oil. The base is so terribly absorbent that I can't manipulate the first oil layer. Soon after I start with oil paint doesn't flow normally, which doesn't allow me to keep going.

I have done many tests and when I isolate ET with Paraloid B72 or an oil medium (1 part stand oil + 2 parts turpentine, for example) the brushability improves considerably. The base is still absorbent, but it allows me to work on it.

Is there a better alternative to an isolating varnish? I am concerned about the preservation of my paintings, but this issue just doesn't let me keep painting.It may be a silly question, but... would it be more reasonable to apply an isolating coat with an emulsion medium? I mean, mixing an oil medium with an ET medium. For example, the medium I am using to grind my ET colours with 1 part stand oil + 1 or 2 parts turpentine. Any other suggestion maybe?

Thanks again.


isolating coat over egg tempera grisaille

Question asked 2020-02-18 15:25:41 ... Most recent comment 2020-02-19 09:00:07
Varnishes Egg Tempera


I have serious doubts about what kind of isolating coat would be most appropriate for me.

I'm looking for a varnish to seal egg tempera that is also compatible with a final varnish, which will go over the last layer of oil.

As the isolating coat penetrates over the tempera, it becomes part of it. I would like to know, according to your criteria, which combination of varnishes I could use.

Here is the structure of my paintings:

Egg tempera underpainting in grey values. This layer is extremely matt, due to the fact that I thin the ET with a lot of water. Then I apply combined oil glazes and intensify the lights with white tempera grassa (highlights). Finally I finish the painting with oil paint.

I have tried Paraloid B72 (15%) by Kremer and it is completely transparent. The problem is the brushability. So I only manage to apply it in small areas. It is impossible to give a uniform layer to the whole painting and I prefer not to spray it.

I have tried Gamvar (Gamblin) as well. The brushability is great, kind of gelatinous. But even after drying it is still a bit yellowish or dark. And I am not sure if it is compatible with ET.

One last question. In the following link it says that if adding UV light stabilizers to the varnish it should be added to both layers (isolating coat and final varnish), what do you think?

Thanks a lot in advance and best regards.


Using Gatorfoam board as a rigid support for watercolor paper

Question asked 2020-02-18 13:41:28 ... Most recent comment 2020-02-18 15:29:06
Rigid Supports Watercolor

​I have heard watercolor artists and seen utube videos by watercolor artists promoting adhering watercolor paper to gatorfoam board as a permanent, rigid support.  The watercolor painting is varnished when complete.  

I was looking at using the gatorfoam board in this way for a large (36" x 48") watercolor painting I plan to do.  While the artists mentioned seem to believe the gatorboard is acid free and archival, I'm concerned that it may not be.  It is light weight, strong and very rigid which make it appealing as a support but I'm concerned about the long-term effect on the watercolor paper and painting.  Please give me your opinion.  Thank you!

Low Cholesterol Eggs

Question asked 2020-02-14 14:23:04 ... Most recent comment 2020-02-14 14:17:00
Egg Tempera

I have a student working with "lower cholesterol" eggs, marketed as having "25% less saturated fat", to make egg tempera paint. She's having a hard time geting her tempering correct.  The obvious answer is that there isn't enough egg oil in the yolk for her to make a good paint film - yes?  Any other considerations regarding working with low cholesterol eggs?  Needless to say, I'll encourage her to switch brands.

Koo Schadler

question on spray lacquer

Question asked 2020-02-11 21:31:19 ... Most recent comment 2020-02-13 14:02:43
Industrial and Non-Traditional Products

​I do multi-media work on Ampersand's panels and use multiple coats of Golden's archival spray varnish as a protective coating. Recently, out of curiosity, I lightly sanded Golden's gloss varnish and top coated it with 2 coats of nitrocellulose lacquer. To  my surprize, nothing terrible happened, at least visually at this current moment in time. 

I understand that lacquers are a no-no do to their propensity to crack and amber with time. But, could they be used on top of an archival varnish solely for the purpose of aesthetic reasons? I have always been told that brittle products can't be used on softer ones, but I have been asking myself: so what if the nitrocellulose lacquer cracks and slightly ambers in 100 years? (A person I spoke to from a lacquer manufacturer told me that today's Nitrocellulose lacquers are not the same as the ones first developed), that they take a much longer time to crack and significantly yellow).  As long as Golden's archival varnish is the actual protective layer (used as the permanent layer), couldn't two thin coats of spray lacquer be removed by physically sanding it off? And since lacquers re-wet themselves, couldn't the picture just be recoated with new lacquer, or a new invention(hopefully after a 100 years) that isn't so plastic looking?

Grateful for any thoughts,


Oil Painting on unprepared hardboard (Masonite)

Question asked 2020-02-07 15:28:17 ... Most recent comment 2020-02-07 15:54:04
Oil Paint

​A customer of mine—I run an art store—came in saying he painted an oil painting 20 years ago "on Masonite" with no surface preparation. He says it looks the same, but is wondering if he can do anything to help its longevity. (Aside from cleaning and varnishing.) Any advice since the substrate was not sealed? What is he up against?

Painting on wood

Question asked 2020-02-06 10:57:55 ... Most recent comment 2020-02-06 15:54:19
Acrylic Grounds / Priming Oil Paint Rigid Supports Sizes and Adhesives Watercolor

​1. When painting with acrylic followed by oils on wood panel 

(specifically birch veneer) is it best to seal the wood first with acrylic primer such as kilz followed by gesso?

2. When stretching canvas over wood panel is it best to prime the wood panel first, then stretch followed by gesso?

3. If glueing canvas to panel, prime first? What glue is best to adhere canvas to panel? 

Painting on wood

Question asked 2020-02-06 10:50:39 ... Most recent comment 2020-02-06 10:41:00
Acrylic Drying Oils Gouache Flexible Supports Grounds / Priming

I have always painted with acrylic, often followed by oil on canvas. 

Am exploring painting on wood panels, specifically birch veneer.


1. Should I seal the wood first with primer (kilz) followed by 


2. If I glue canvas to wood panel before painting what glue is

best and do I still prime the wood first followed by gesso on canvas?

3. What substance do you recommend for gluing paper onto

wood panel? 

Thank you so much for your help!

Fixitive before Egg Tempera?

Question asked 2020-01-30 11:53:47 ... Most recent comment 2020-01-31 09:19:03
Egg Tempera

​I am very new to egg tempera painting. I have completed a drawing in pencil on a gesso panel. I am wondering a couple things:

1. Is it necessary to india ink over the pencil?

2. If I dont do an india ink underdrawing on top of the pencil, will the pencil mix with the egg tempera paint and make it muddy?

3. If I spray a fixitive (like a krylon drawing fixative) over the drawing will it negatively affect the tempera? 

4. Has anyone found that using india ink over pencil helps to seal the pencil and prevent it from mixing with the tempera?

Substrate for marbling and oil

Question asked 2020-01-14 22:34:27 ... Most recent comment 2020-01-31 07:48:35
Grounds / Priming Gouache

​hi there, I'm trying to make large 6 x 8ft marbleized surfaces that I will then paint with oil on top. I'm having trouble finding canvas that is white enough and unprimed at that scale. My options as I understand them are,:

Apply alum to paper, marble the paper, adhere to canvas, apply matte medium , paint oil on top

Apply alum to 100% cotton bed sheet, marbleizing,  stretch on its own or over canvas, apply matte medium, oil paint on top

Or apply golden absorbent ground to primed surface, apply alum,  marbleize, apply matte medium, oil paint over

Or? Any other ideas? Will alum have any negative effects? Can paper be adhered to canvas and then painted over? Bed sheets with high thread count? What are the most durable options here? Thanks!!! 

Black oil - is it beneficial?

Question asked 2020-01-15 16:52:10 ... Most recent comment 2020-01-28 16:56:38
Oil Paint Drying Oils


I'd like to ask about black oil (leaded oil). I found somewhat contradicting informations about it.

Natural Pigments sells "Dark drying oil (Black oil)" and the description says:

Dark Drying Oil or black oil is a fast drying oil made by heating linseed oil with lead oxide (litharge) and used in historical oil painting. The lead (metal basis) content of our dark drying oil is about 3% by weight.


Black oil can improve the handling and drying of oils and can be used in recipes to make megilp, Maroger and Roberson's mediums and traditional oil varnishes, such as copal.

I'm not interested in Maroger and Roberson mediums, or traditional oil varnishes, but the statement "Black oil can improve the handling and drying of oils" sounds intereseting to me. As far as I know certain lead compounds speed up drying of the paint film and/or increase its flexibility and durability. Thus, it would seem to be useful medium.

However in MITRA pdf article "Myths, FAQs, and Common Misconceptions", there is this statement in the last chapter about Maroger mediums on page no. 11: "Dr. MarionMecklenberg of the Smithsonian Institute’s Museum Conservation Institute,however, has shown that paint films containing even small amounts of leaded oilare substantially weaker than those containing only cold pressed linseed oil."

Of course I realize that the actual amount of black oil in medium/binder can have varying effect. But generally - how is it with black oil? Can it provide any advantages, e.g. better balanced through drying of paint film and increased durability, or not?

"Beading up" or reticulation of oil paint

Question asked 2020-01-24 10:19:42 ... Most recent comment 2020-01-24 19:38:24
Grounds / Priming Oil Paint Other

​Hello Everyone,

Im currenty grinding my own colors and starting to paint with them. But im running across a problem and thats the beading up of certain colors.  

After trying to find answers online , it seems that this occurs because  my surface has a  lower surface energy than the paint.  If this is correct it seems that I have two options, I either have to change the surface or change the paint.  

Would spraying alcohol on my surface work? Or thinly oiling out and letting it dry? What can I put on the surface that would make the paint stick better?  Can I add something to my paint?  

P.s. I cant sand the surface since i did an underpainting and i dont want to damage it. 

Best Regards,


Support for Large Scale Egg Tempera Painting

Question asked 2020-01-16 12:15:18 ... Most recent comment 2020-01-22 11:19:35
Rigid Supports


I reviewed prior questions and comments in the "rigid support" forum before posing my question. I've been using 1/8" hardboard, cradled approximately every 12" with kiln-dried douglas fir 1" x 2" stripping. This seems to work fine. I do apply 8 coats of traditional gesso front and back, finishing with one coat of alkyd paint on rear per Koo Schadler's instructions.

My main issue is weight. On a 4' x 8' panel this becomes very heavy. I need the help of a friend to move it at all.

Is there a lighter weight material that I could safely try? I wrote to Simon Liu but he says his panels are not safe for traditional gesso.

What about coroplast, or an archival foamcore type material?  I could still cradle it with wooden strips for rigidity and would be willing to glue a muslim layer on. Any ideas for lighter weight materials?

An advantage of my system is, of course, that it is dirt cheap but i would be willing to pay quite a bit more for a lighter weight solution.

Two other issues:

1. It is almost gospel that we are to use untempered (standard) hardboard, but I've heard from manufacturers that the amount of oil or resin in modern hardboard is miniscule and actually adds to the integrity of the board, as untempered does tend to chip more at the edges. Perhaps at this point it is just myth that the oil will migrate through to the gesso and affect the painting? For a long time I could not source untempered hardboard in California except by ordering 100 sheets shipped by freight. But now I can buy it locally but I'm wondering if tempered may actually be better?

2. The logic behind applying equal number of coats of gesso, front and back is to equalize the forces in order to prevent warpage. However, the hardboard that is available to me has a "screen back" so it absorbs more gesso. Plus the rear has cradling which also affects the amount of gesso, so is perhaps appling equal coats no longer necessary or, in fact, should I be quantifying the amount of gesso applied either by weight or volume to ensure that the amount is equal on front and rear?

That's it! Thanks so much. It is comfortaing and amazing to have this in-depth MITRA forum available to us artists.

Lora Arbrador

Loom sized linen

Question asked 2020-01-20 00:38:27 ... Most recent comment 2020-01-20 15:41:26

What is the standard size used in​ Unprimed linen and is it advisable to remove it with gentle washing before users sizing and priming?


Soy oil for printing

Question asked 2020-01-08 11:20:39 ... Most recent comment 2020-01-17 17:45:49
Drying Oils

​Hi, my collegue from the Printing Departement on my academy, recently switched to soy-based printing inks. These are made watersoluble, so we need no mineral spirits for cleaning anymore.
His complaint, however, is that the inks dry very slowly, as in at least a week, or so. This does not work, at an art academy. So he asked me for advice, but I do not know of soy oil being used as oil for paints or inks. Is it even a drying oil?

Does anyone here know what to do? Is there a way to let these inks dry faster (cobalt dryer?) Or is it 'dead on arrival' and should we use a different inkt?

I hope you can help us with this, thanks in advance.

How to store egg tempera paintings

Question asked 2019-12-12 23:56:18 ... Most recent comment 2020-01-15 12:13:14
Egg Tempera


I'm aware that the optimal way to store an egg tempera (or any painting) is to place it upright in a rack. None of the paint-bearing areas of the painting should be touching the slats of the rack. Two questions:

1. I would feel more comfortable covering it with some loose plastic or something in case of leaks. I understand that as long as the painitng is upright water will bead off of it. But still I would feel better if there was some sort of barrier.

2. Living in an apartment and not having a rack for paintings, plus some of my ET's are as big as 4' x *8 I'm trying to figure out how to safely store them. I used to wrap them in cloths such as sheeting and then wrap with plastic. I would like to be able to store them flat. 

Any ideas?

Thanks much, Lora Arbrador

Gamsol v/s Turpentine: Safety + Surface Quality

Question asked 2020-01-06 22:56:08 ... Most recent comment 2020-01-14 09:41:42

I was recently discussing ways to mitigate surface irregularities during the painting process, as opposed to varnishing, with a specialty paint merchant. They recommended reducing the amount solvent in my medium and using a less bodied oil like walnut for flow, which seems like good advice. However, they also recommended switching from Gamsol to double rectified Pine Turpentine, which I have questions about.

I currently use a 50/50 mix of Gamol and Linseed oil and my paintings aren't too many layers.

I know Turpentine and Gamsol have a different feel under the brush, but would turpentine actually help to create a more mat, uniform surface? 

The merchant disagreed with me about Gamol being a less toxic solvent, which I've always been told. If I'm understanding the MITRA Resources pdf on solvents (word in parenthesis my own)- "Aromatic hydrocarbons (like turpentine) tend to evaporate more slowly and are more toxic than aliphatic hydrocarbons (like Gamsol)". Can you confirm that Gamsol is indeed safer?

Thanks in advance for any thoughts!

Diluting retouch varnish

Question asked 2019-11-25 17:42:53 ... Most recent comment 2020-01-11 22:50:11


Can retouch varnish be diluted to make it less shiny, and if so, with what?

Thank you!

Beading of oil or varnish on a dried oil paint surface

Question asked 2020-01-06 18:38:12 ... Most recent comment 2020-01-07 17:34:24
Varnishes Oil Paint

 when trying to oil out dull areas, glaze or put a varnish over my paintings in some areas the medium, varnish or thinned paint just beads up. It is difficult to cover with anything except straight paint. I use Williamsburg and Winsdor and Newton paints lightly thinned with linseed oil on a lead grounded high quality linen canvas. I've been told to use toluene in the varnish or medium. 

Cooking oil as a medium

Question asked 2019-06-21 08:50:41 ... Most recent comment 2020-01-06 18:40:45
Oil Paint Paint Mediums

​On various art forums people often ask about using grocery store cooking/salad oils, such as walnut oil, as a painting medium. They are usually trying to save a bit of money. It seems like a false economy that could likely cause probelms down the road and negate hours of work put into the paitning process just to save a few dollars on materials.  I'm aware that there is an obvious problem with some grocery store oils containing added anti-oxidents to maintain freshness.  Are there other issues, related to the differences in how edible oils are processed as opposed artist grade oils, that can cause problems in the quaity of paint film formed?


Question asked 2020-01-06 11:00:15 ... Most recent comment 2020-01-06 18:22:26
Egg Tempera Environment


I've had several people ask me about mold issues on egg tempera paintings.  I understand that the porous, high PVC surface of an unvarnished tempera is more prone to mold (since moisture more readily enters in).  My questions are:

- How detrimental is mold on top of a paint surfaces (both on other mediums generally, and egg tempera specifically)?  

- Aside from taking the work to a professional conservator to clean, what can a person do?  I've known people to wipe the surface with alcohol, which seems to work well in removing the mold; however I'm concerned it may compromise the paint film if applied to liberally (abrade with applicaiton, or sink in and lead to embrittlement).  What about using Phenol?

- A person recently wrote me with this question and wondered how consequential mold was for past painters, given that they did not have climate controlled spaces.  Do you know if mold was  historically a big problem? 

Koo Schadler

Gesso Ratios

Question asked 2019-12-27 09:21:36 ... Most recent comment 2019-12-28 13:03:39
Grounds / Priming

Hello All,

In making gesso, my experience is to first establish a ratio of glue to water, my preference being 1 pt. glue to 16 pts. water (1:16).  While I've always believed there is some variability in that ratio (my guesstimate, from 1:12 to 1:20), a past MITRA question clarified that, given the complexity of glue, the variability can be greater than that (i.e. one paint company recommends a 1:5 ratio) - it all depends on glue factors. 

Anyhow, the second relevant gesso ratio is glue water to chalk or gypsum (whiting).  The most common ratio I see (and use) is 1 pt. Glue Water: 1.5 pts. Whiting.  This generally yields a gesso with the consistency of light cream or whole milk, ideal for applying gesso.  Too thick a gesso is more apt to crack.  

The Mt. Athos monk with whom I've conversed in the past is asking another question, relative to the above.  His gesso recipe, like mine (1 glue: 16 water + 1 glue water: 1.5 whiting) is yielding a gesso with a heavy cream or pudding consistency.  He is asking which is more relevant: staying with consistent ratios (even if it yields a thick gesso), or shooting for a gesso consistency of light cream (even if that means adding less whiting).  My gesso never yields a pudding-like gesso, so I'm puzzled why he's getting that.  Regardless, I would say consistency is more important - applying pudding-like gesso is not good.  But then again, gesso is essentially a high PVC paint, and if one too dramatically alters a paint's PVC, isn't that problematic?

I realize all this is complicated by variabilities in ingredients and measuring, environmental factors, etc.; and there is not a simple answer.  Nonetheless, I welcome general thoughts on the above, as well as a response to the specific question of which is more important: staying with consistent gesso ratios, or adjusting a ratio (perhaps dramatically) to yield a thinner gesso consistency.  


Koo Schadler

How to label the back side of an oil painting on canvas

Question asked 2019-12-11 23:35:33 ... Most recent comment 2019-12-16 00:40:31
Matting, Framing, and Glazing Oil Paint Flexible Supports

​Forgive me if this is answered elsewhere, but I'm looking for the best practices on labeling the back side of a painting on canvas on strainers. I'd like to include a professional description of the date, materials, and name/authentication of the work, etc. I've mostly only seen artists doing this in the past on panel by attaching a label, as in J. ALbers, but have heard adhering anything to the back of the piece will eventually disrupt the front tension- similar concerns about writing directly on the piece, and furthermore only labeling the stretchers seems to miss the mark. Perhaps on a dust cover, but this seems impractical on a larger piece... Any industry standards?

Many thanks,


Tempera grassa ground

Question asked 2019-11-03 17:58:26 ... Most recent comment 2019-12-10 11:09:23
Egg Tempera Grounds / Priming Oil Paint

​Dear MITRA administrator,

Which ground would you suggest for painting with egg-oil emulsion (tempera grassa)?

Ground should go on rigid support like wood panel. Emulsion ingradients are: linseed oil, egg and water in different ratios, nothing else.

Damir Pusic.

Watercolor surface identification

Question asked 2019-12-02 12:17:37 ... Most recent comment 2019-12-02 15:14:31

I have a watercolor piece by Albert Herter that I estimate to be from between 1894-1900 by the name of "Gift of Roses". I've been working on identifying it the past few days and have a few questions about watercolor surfaces from that period. When we looked at the back of the piece, I was suprised to see that it was on a kind of pressed board, and not paper as I thought. I did not remove it entirely from the frame to avoid damage, so it may be mounted, but the edges seem to be consistent, no paper glued, just painted directly onto this board.  I have pictures of the front and back for anyone that wants a look here

I'm a painter myself and am pretty certain it's not a print or crayon enlargement, but the surface has me questioning that.  Any help would be greatly appreciated. 

rheology of painting for glazing

Question asked 2019-11-30 20:46:58 ... Most recent comment 2019-12-02 12:40:11
Oil Paint

​Hello Mitra,

I always see people watering down there paints when they are going to make a glaze.  Many books talk about avoiding this bc if one goes extremely past the CPVC this will create an unstable film.  Is there a way to guage the making of paint for a glazing technique?  Is there some sort of general rule or rule of thumb that one should take into account when mixing paint for a glazing technique? 

Best Regards,


Repairing cracked masonite panel

Question asked 2019-11-27 21:52:02 ... Most recent comment 2019-11-30 13:12:39
Handling and Transportation

​A fellow artist and I collaborated on a piece together, in both acrylic and oil paint on a 36"x48" cradled Gessobord. I applied ArtResin to the piece which was curing perfectly in the storage area on the third floor of an art gallery. I went up to the painting on the third day and found a couple of deep cracks had appeared in the glossy ArtResin. Upon closer inspection I realized the cracks in the resin were a symptom of cracks in the masonite panel. Since it was in perfect condition two days prior, and it wasn't subject to wild fluctuations in temperature, I assume it fell and someone righted it, not realizing it has suffered. 

Now the other artist has been invited to ArtBasel and wants to take this piece. My question is; how can I repair the masonite so the end result is strong and also looks good enough should the piece sell?

I think I have figured out how to repair the resin by sanding it down and reapplying it, but any suggestions for that part are also appreciated.

Thanks in advance!

Studio safety of W & N Artisan thinner

Question asked 2019-11-25 17:41:40 ... Most recent comment 2019-11-28 14:46:31
Solvents and Thinners


recently read an article on this forum re water-miscible oils (2019-11-16) . This has rekindled my interest in using them again. I first started using W & N Artisan oils over 10 years ago, and off-and-on since. Problem is that if you use water as a thinner it evaporates almost instantaneously leaving a very short open-time. This was a big turn-off for me.

I have got their associated thinner (Artisan THINNER) which stays open for at least an hour and great stuff for altering an initial drawing/lay-in. (I only use it for the initial drawing). On specific questioning W & N advise to use a maximum dilution of 1:2 by volume ( 1x part oils : 2 x parts thinner). I usually use a bit less thinner than this. They stated that it was non-toxic also. (I realize that there can be a problem with this description in some cases) 

At the above ratio it does all the things I used to use turps for and, hopefully, a lot less toxic. Which is what I really want to know, ie., just how safe is this thinner?

I checked the MSDS for the product which states that: " This product has been certified by ACMI to carry the AP (Approved Product) seal, meaning this product bears no chronic or acute human health hazards". The Artisan literature also states exact same reference.

Specifically, under the heading 'Inhalation' it states no specific symptoms known. Also, not classified as a specific target organ toxicant after repeated exposure. Skin contact also had "No specific symptoms known".

The only caution was that it could cause irritation to eyes and mucous membranes; also that thermal decomposition.......may include harmful gases or vapors. However, is stable under normal ambient condions.

Initial boiling point >100 deg.C at 760mmHg.

In my home studio I have a portable fan that I could place in the windows, but the noise is irritating.  I also have open windows. However, in the colder weather I can only have them slightly open (there is a small cross-flow thru these windows from facing rooms) because my hands have an extreme reaction to the cold. If I opened the windows to any large degree I would have to wear gloves so thick that I could not handle a paint brush.

Can I safely use this Artisan thinner with minimal cross-ventilation (I only use about 2 - 3 mls (5 mls at the absolute max.) during any one session)?

Do you have any other information that could cause me to be more cautious?

Really appreciate your expert advice, as usual.

Many thanks in advance.

Repairing cracked masonite panel

Question asked 2019-11-27 21:51:13 ... Most recent comment 2019-11-27 21:38:00
Rigid Supports Handling and Transportation Art Conservation Topics Industrial and Non-Traditional Products Other Studio Tools and Tips

​A fellow artist and I collaborated on a piece together, in both acrylic and oil paint on a 36"x48" cradled Gessobord. I applied ArtResin to the piece which was curing perfectly in the storage area on the third floor of an art gallery. I went up to the painting on the third day and found a couple of deep cracks had appeared in the glossy ArtResin. Upon closer inspection I realized the cracks in the resin were a symptom of cracks in the masonite panel. Since it was in perfect condition two days prior, and it wasn't subject to wild fluctuations in temperature, I assume it fell and someone righted it, not realizing it has suffered. 

Now the other artist has been invited to ArtBasel and wants to take this piece. My question is; how can I repair the masonite so the end result is strong and also looks good enough should the piece sell?

I think I have figured out how to repair the resin by sanding it down and reapplying it, but any suggestions for that part are also appreciated.

Thanks in advance!

can linseed oil be used as a sizing/sealing agent

Question asked 2019-11-23 01:43:43 ... Most recent comment 2019-11-23 10:59:02
Sizes and Adhesives Rigid Supports


A poster at the Wet Canvas forums recounted priming a panel with linseed oil. I recommended caution, never having heard of, or used, this technique. Others supported the practice, and said linseed oil would preserve the panel, and would dry to form a good sealant, suitable for painting. An internet search reveals no definitive argument one way or the other. I wonder is there a "last word" on the subject? Cheers!

Stapling canvas: sides or back

Question asked 2019-11-19 16:51:23 ... Most recent comment 2019-11-22 09:58:59
Flexible Supports

I seem to remember reading somewhere long ago (perhaps the old AMIEN forum) that stapling/tacking on the back was purely aesthetic and stapling on the side provided more stability/even tension and so was archivally preferable. Does anyone here have insight into this? Thanks.

Water-Miscible Oils, Revisited

Question asked 2019-11-16 13:22:49 ... Most recent comment 2019-11-19 18:39:44
Oil Paint

​Hello MITRA folks. I've inquired about water-miscible oils (as a option for underpainting) here before, and the response was that there was some concern about their long-term stability, being a relatively new product, because of some of the surfactent ingredients in some of the products on the market. Do you know if there are brands that do NOT incorporate these questionable ingredients? And if there are working practices that would mitigate any possible de-laminating effect down the road? On a related note, could using egg tempera (in the tube product form) be a reasonable substitute for washy underpainting techniques for an oil painting? I'm looking for a solvent-free option that is fluid, longer open time than acrylics, and one that can be left exposed in some areas (i.e. edges) of the finished oil painting. Thanks for any thoughts!

Mounting and framing works on paper

Question asked 2019-10-29 15:40:17 ... Most recent comment 2019-11-09 19:25:28
Matting, Framing, and Glazing Sizes and Adhesives

​Hello dear people from MITRA. 

I wanted to ask some questions about framing and mounting..

I don't know is this an issue in other countries and cities as well, but here in my country i have a serious problem with people who are framers, and with their method so to speak... 

They use mostly masking tapes (or painters tape) i think this is how you call it, mostly yellowish tape that can be ripped with hand easily.

They take the artwork on paper (watercolor, drawing etc.) and place it under  the passe- partout (mat). Then they use masking tape and put it on the 4 corners on the back of the artwork on paper so it will stick to the passe partout. Then they put glass on the front, and for the back they  use cardboard to press or hold the artwork and passepartout together . Close it, and that's it... 

So, i have seen that the right way to frame works on paper is to take conservation (archival tape) to mount the artwork on archival museum board (which they have never heard of) and then to put together passepartout and museum board so that passepartout will just lay over the artwork, Then glass on front, and cardboard on the back and to close the frame...

Since i cannot change their decades old way of framing i have found a store where i can at least buy the archival tapes. 

They will use this tape on the back corners of the artworks to hold it to passepartout. 

So can anyone please advise me which ones to buy for this?  (i will post links)     

(These ones are conservation tapes made of archival safe poliester which is put together with acid free paper with selfadhesive lining. 

and these ones    are a conservation corners (or photocorners) . They are made of 100 % acid free, archival, safe  polypropylene . It contains longlasting acrylic adhesive , 100 % water based

I think i would like to buy the archival tape (1st one) but if there is anyone who can check this and advise me on this, i would be more than grateful. 

Also if anyone thinks there is another solution to this, please say so.  Thank you all very much!

Kind regards

Marko Karadjinovic

yupo paper

Question asked 2019-11-03 15:49:52 ... Most recent comment 2019-11-05 16:42:40
Art Conservation Topics

​Can you paint on yupo paper with oil and will it absorb enough to not peel off over time.  Is it archival/

Gamvar for egg tempera or alternatives

Question asked 2019-10-22 11:46:42 ... Most recent comment 2019-10-31 04:26:45
Varnishes Egg Tempera

​I have a question about varnishes for egg tempera.  Until recently, I used boiled linseed oil, but it is a tremendously problematic varnish which changes the nature of painting (lead white becomes transparent, azurite becomes green etc.)  So I decided to seek something better.  Several substances came to my attention, one of them was GAMVAR.  I tested it and got very unpleasant surprise: wherever Gamvar came into contact with egg tempera paint, dreadful white spots appeared.  NOTE: those were not "blooming", I'd know the difference.  This was some kind of whitish residue that appeared on top of the painted layer, while Gamvar completely sunk into the paint.  Under-tempering is not a factor in this, I temper my paint quite well (egg-shell sheen), and apply nourishing layers often.  I also know that those whitish spots look exactly like when I had to clean gilded parts with mineral spirits, some of it got onto the paint and bleached it immediately.  

My friends who work in oil swear by Gamvar.  I decided to persist and varnish the painting I just finished with Gamvar, and even after 6 consecutive coats, there are lots of sinking as if it goes through the paint like through a sieve.  

Anybody had experience with this or has other varnishing options for egg tempera?  The properties I seek are:

1. Non yellowing
2. Something which would not cause blooming
3. Reasonably strong to protect the painting

High humidity for large canvas

Question asked 2019-10-23 09:46:39 ... Most recent comment 2019-10-24 04:27:21
Flexible Supports Storage Matting, Framing, and Glazing

​A student of mine just asked how she can protect a large cotton canvas from the really high levels of humidity in her new house.

The canvas was passed down to her and it belongs to the family. It is too large to mount on a panel. Because the walls are quite humid in the winter, she fears for the longevity of the painting.

I remember reading suggestions of gilding the back of the canvas of aluminium foil etc. Do you have any suggestion for this problem?

Thank you


Phthalo Green mystery

Question asked 2019-10-02 12:09:29 ... Most recent comment 2019-10-19 14:54:34
Paint Making Paint Additives Oil Paint Scientific Analysis Pigments

Hello all,

I have a bit of a minor mystery that I'm hoping you can help me with.

I have been testing a lot of different paints from various brands when mixed with walnut oils to a more fluid texture and stored in the dark in a box in a wardrobe at room temperature.

This was to find the paints that stay open the longest without the use of clove oil, or other techniques.

As part of this I tested 9 different paints of either PB15 or PG7 (and in one case, a mix of both). From these tests I concluded that Phthalo pigments are indeed fast dryers as all of them except one totally dried in 2-8 days.

The one exception was a tube of Royal Talens Van Gogh Phthalo Green (PG7). This was still open for a few weeks when I had to stop the test and go on holiday. When I got back I thought I'd test all the colours to see if any were still open after all this time.

To my astonishment the paint was still open after 62 days! I then took the paint sample out of the dark and left it in a normal lit room for at least 3 weeks, after which it dried. The smell of the paint is the same as Linseed oil, the texture upon drying is firm (not soft) and the colour the same as other PG7 paints.

I tested this again with both pure paint and paint mixed with wallnut oil, again it stays open even for a few weeks exposed to the light.

I can only think that this paint has been exposed to some kind of anti-oxidant such as it used to preserve cooking oils, as I can't think of another reason why it stays open so long.

I would like a long drying PG7 paint, but I'm concerned about the resulting paint film integrity with using this paint.

I have emailed Royal Talens, but no response yet.

I was hoping you have some thoughts about what might be happening here?


Laser light damage?

Question asked 2019-10-06 15:31:17 ... Most recent comment 2019-10-08 15:52:01
Mural Painting Art Conservation Topics

​About four years ago I was in the Basilica of saint Francis of Assis and there were a number of what appeared to be friar guides using laser lights to direct their groups eyes around the murals high above them.  Could this be damaging to the pigments in the paintings? Hindsight is 2020, but instead of asking them directly I went to a guard and asked if they should be doing this.  "I understand but it's out of my control."

Were my concerns valid ones? I've since noticed it being done, if more briefly, on stained glass windows in the Chartres Cathedral as well.

Regalrez 1126

Question asked 2019-10-08 07:41:37 ... Most recent comment 2019-10-08 11:32:41

​just curious how to adjust the sheen of regalrez 1126?

Wheat and Rice Starch Adhesive Vs. Other Starches

Question asked 2019-10-07 02:45:01 ... Most recent comment 2019-10-07 21:42:04
Sizes and Adhesives

​Hi there! This might be a slightly esoteric question, but I was curious about the use of starch paste as an adhesive for use in paper artifact conservation.

Why are wheat and rice starches favoured over other types of starch, for example corn or potato starch?

Is it due to the ageing properties of the starch itself (I'm thinking for example of how simple wheat flour paste ages poorly due to the gluten content, though this presumably would not be the case with corn or potato, even in unpurified form)?

Or is it other qualities of the adhesive, such as reversability, cost, ease of application etc?

Thanks in advance!

Restoring unvarnished oil paintings

Question asked 2019-10-03 14:39:51 ... Most recent comment 2019-10-07 16:27:42
Art Conservation Topics

​Dear administrator,

I'm thinking whether to varnish or not oil paintings. 

Is it possible to clean old unvarnished oil painting in same methods as restaurator would do with varnished one?

Also, what would be expected result in comparison between the two?

Kind Regards,

Damir P.

Washing unused canvas

Question asked 2017-10-12 15:58:50 ... Most recent comment 2019-10-04 07:44:12
Flexible Supports

Is it safe to wash unused canvas in the washing machine? If not, can it be washed by hand? I came across a lot of 15 oz. cotton but it has some dirt in spots and deep creases that can't be ironed out.

tempera grassa

Question asked 2019-10-03 14:13:35 ... Most recent comment 2019-10-03 16:53:06
Egg Tempera

​Hi maybe you can answer this one. I've always assumed that you could safely paint oil on top of either acrylic, tempera or tempera grassa. But not in the opposite order. But today I met a seasoned painter, who argued that in the isolated case of tempera grassa, you could also paint on top of lean layers of oil paint without it causing any problems. This was because this oil-egg emulsion contained oil as a binder. What you think. I can't find any evidence online to substantiate this.

Metalpoint Grounds

Question asked 2019-10-01 15:03:12 ... Most recent comment 2019-10-01 20:25:47
Grounds / Priming Drawing Materials

Hi.  I'm doing more metalpoint ground experiments and have a few questions.

1. Does anyone know relative hardness (i.e. which is softest, which is hardest) of a cured film of the following binders: gum Arabic, egg yolk, casein, acrylic polymer, vinyl polymer, and oil?    I'm primarily working with water-based metalpoint grounds, but I made an oil ground and found that it works really well; it seems to abrade better than other surfaces, once it has fully cured.  So I'm wondering if an oil base is that much harder and resistant to a metal nib than the above water-based binders. 

2.  Gordon Hanley is a metalpoint artist who, apparently, (as seen in online reproductions of his work) achieves authentic blacks in his drawings (whereas most metalpoint artists get no more than deep grey).  He says he gets black by working with pure silver on a homemade, proprietary ground. Many metalpoint artists would like to know his secret, but he stays mum.

I made an oil based ground that consisted of 1 part Gamblin Brilliant White Oil Paint, 1 part silica, 1 part Liquin.  Not sure how durable such a combo is, but it did yield very dark marks - and, after sitting for a few months, I just noticed that one set of marks now appear genuinely black. (To my annoyance, I didn't note what metal nib made those mark).  The questions are: how durable is that combination of ingredients? And is there anything noteworthy in those ingredients that might account for deep grey metal marks turning black?

3.  I've played with adding different extenders (silica, bone ash, glass, barite, pumice, marble dust, chalk, historic pigments) to metalpoint grounds, to increase abrasion.  Silica gives the best results, which isn't surprising given its Moh's Hardness Scale rating of 7 (harder than any metal nib I use).  What is surprising is that Talc, with a MHS number of 1 (much softer than my metal nibs) also seems to minimally increase abrasion.  I've read up on the properties of talc but it's confusing for a non chemist to distinguish between natural versus milled state, etc. - I just don't understand it all. So my question is, does anyone know properties of talc (i.e. does it have an unusually rough morphology?) that might explain why it improves a metalpoint surface?  Is it accurate that all minerals, even after they've been milled, have an irregular morphology (versus, for example, some modern pigments that are quite smooth and round at the particle level)?

Thanks as always,  Koo Schadler

Underpainting and/or underdrawing for Encaustic

Question asked 2019-09-28 03:12:42 ... Most recent comment 2019-09-29 04:48:58
Encaustic Drawing Materials Egg Tempera Ink

​Hi All,

I am new to this forum and look forward to benefiting from the expertise gathered here.

I am currently working on a project that will involve 13 small panels (each one approximately the size of an A5 piece of paper) to be painted in encaustic - according to a preestablished design (each design being different). The panels themselves are 3 mm HDF panels coated with size and then several thin layers of traditional RSG and chalk whiting gesso. 

So I want to create an underpainting and/or an underdrawing to assist in the image creation before applying the encaustic paint. I'm thinking of using washes of india ink for my underdrawing as well as light washes of egg tempera to begin to establish color relationships. Are either one of these materials going to create an adhesion problem for the wax? I'm thinking not, but wanted to be sure. Of course, I do plan on fusing the painting by "burning it in", as this will allow the melted wax to fuse properly with the ground.

I did create a painting this way approximately 7 years ago. There was not then nor appears to be now any adhesion problem. But I thought I would check with the experts here as most current usage of encaustic appears to be at least fairly coarse if not abstract, so I do not easily find much information on creating recognizable or even detailed images using this technique.

Thanks in advance for your information.

Silverpoint and Egg Tempera

Question asked 2019-09-19 15:20:22 ... Most recent comment 2019-09-20 16:51:23
Animal Glue Egg Tempera Varnishes Drawing Materials

I have a fellow painter asking me about a piece she is creating in silverpoint and egg tempera.  As she rightly points out, the sulphur in egg yolk causes silver to oxidize (in fact, a bit of yolk is sometimes added to metalpoint grounds to speed up oxidation).  She may leave parts of the silverpoint visible in the final painting and doesn't want the silver to tarnish.  She is thinking of applying a layer of rabbit skin glue over the underdrawing, to seal it off, before painting in egg tempera on top.  I have a few questions about this:

1.  Because rabbit skin glue is so hygroscopic, would a very thin layer of platina shellac be a better option for sealing off the silverpoint uderdrawing before moving onto tempera?  

2.  I know there are many examples of egg tempera adhering well atop india ink underdrawings, so I understand ET can adhere to shellac - but if an entire panel is coated with a layer of shellac (as suggested above), is adherance of the tempera a bit more problematic?  If so, would a careful sanding of the shellac layer be sufficient to improve adhesion? 

3.  How porous are rabbit skin glue and shellac?  Would they entirely protect the silverpoint from oxidation (from either egg yolk or atmospheric sulphurs), or are they not sufficiently sealing?  Is a final varnish necessary to make sure that the parts of the silverpoint that remain visible don't tarnish?

4. When silverpoint underdrawings were used in the Renaissance, were they pretty much invariably covered with ink layers before egg tempera was applied?  Or are there Renaissance examples of egg tempera painted directly atop silverpoint?  I'm wondering, if egg tempera is applied directly onto silverpoint (no ink layers in between), do the tempera paint layers sufficieintly seal off the silver from oxidation, or does enough oxygen travel through the tempera to reach the underlying layers and cause the silver to oxidize if in direct contact with the tempera paint layers?  If so, would the resulting oxidation on the silverpoint compromise to any extent the adherance of the tempera to the silverpoint?


Koo Schadler

Stuck oil paint tube caps

Question asked 2019-09-18 02:42:44 ... Most recent comment 2019-09-18 23:04:19
Oil Paint


this is probably one of the dumbest questions you have had, but here goes anyway: I don't always remember to clean the threads on the tubes, and just screw the caps back on after squeezing paint out. I usually get away with it, or having the caps just being a bit tight. But sometimes I may not use that colour for some weeks, or months, and the cap is well and truly stuck. (for some reason it doesn't affect all my tubes).

I saw a video on Youtube which showed someone upending the tube and placing the threaded part into just off boiling water. That  works, although sometimes has to be repeated once or twice more. I then squeeze out the paint that was in the threaded part of the tube and discard it.

I tried to scrape off just the hardened paint holding the cap to the threads, but caps wouldn't budge. Tried using a rag and some multigrips but just broke part of the caps (tubes still salvageable).

Apart from getting my act together and (1) carefully cleaning the threads (and inside the cap) after using the tube, have you got any other better ideas? (2) Is my Youtube hot water method likely to damage the paint in the body of the tube nearest the threads? It seems to look and handle OK afterwards, but just worried that the hot water might damage the paint in the top part of the tube which might cause problems later down the track.

Appreciate your feedback

Drying time for extra acrylic gesso primer to canvas

Question asked 2019-09-18 02:58:56 ... Most recent comment 2019-09-18 22:50:41
Grounds / Priming


How long should you wait between extra applications of this gesso before applying the next coat?

On the container it says to let dry between coats, but I use it to fill in the weave of the canvas to give a smoother surface to apply oil paint on. The canvases are already triple primed by the manufacturer but weave of canvas still obvious, which I dislike. When I apply extra gesso I use a bit of pressure to try and drive it into the weave. I can see/feel when the outer part is dry but can't really know when the deepest part is properly dry.

Does it really matter provided the outer part is dry? state that you should wait 3 days after applying the final acrylic gesso layer before you apply oil paint. Should I wait the same time between coats when applying extra gesso, for reasons given above?

Thanks in advance

Pigment absorption on skin contact

Question asked 2019-09-15 18:49:51 ... Most recent comment 2019-09-16 16:27:53
Health and Safety Oil Paint Pigments

​Dear MITRA administrator,

Can pigment ground in linseed oil without solvent be absorbed in body when one touches wet paint with fingers?

I believe lead white can because M.Rossol writes ''Lead metals, lead oxide and lead nitrate are known to absorb through the skin.'' (Artist's H&S Guide page 157.). But what about others like TiO2, Iron oxides, Cobalt, Manganese, etc?

Kind Regards.

Lascaux Spray Varnish & Wax Medium

Question asked 2019-09-16 08:06:13 ... Most recent comment 2019-09-16 12:02:02

​I have a student who applied ten, thin layers of Lascaux spray varnish on an egg tempera painting; then, after it had sat for a few weeks, applied a layer of Gamblin wax medium on top.  The wax medium felt "sticky" as she applied it so she ended up having to rub it fairly vigorously.  When she lifted her rag, there were traces of pigment on it.  Ten layers of Lascaux, even thinnly applied, should be enough to fully seal the tempera.  It might seem like the solvent in the wax medium dissovled in part the Lascuax, but my understanding is that Lascaux's solvent is alcohol, whereas the wax medium's solvent is OMS.  Am I correct in that?  Any thoughts on what might be going on?

Thanks, Koo Schadler

Paint adhesion to support problem

Question asked 2019-09-12 14:17:56 ... Most recent comment 2019-09-15 01:08:29
Grounds / Priming Oil Paint Rigid Supports


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I have a support that has been stored in my closet for at least ten years. It is Belgian Linen mounted on Mahogany board with Rabbit Skin Glue. It appears to have vertical shiny lines which I would imagine to have something to do with the RSG. The surface does have a slick, slightly greasy feel. 

I began to paint on the panel with a wash of Warm Sepia Extra and Gamsol to do the line drawing as I have done for decades. The head and hair portion are two days old, plenty of time to dry to the touch. When I painted on it the next day the end of my Mahlstick touched a portion that I had done the previous day and took off some paint from the surface of the Warp of the Linen. The next day I took some paint without Gamsol and began to model the darks on the figure. This morning as the video shows I can lightly rub some of the paint away which has never happened before. 

Needless to say I am concerned. Before even attempting to continue I am writing to you, and am shortly on my way to the person that has been making my supports since 1986 so we may possibly see what the problem might be. 

Any insight would be greatly appreciated. I’d like to continue on with this support if possible. My paintings have very little paint on the surface, no medium, and usually about three or four passes.

Chemical Formula

Question asked 2019-09-12 20:51:48 ... Most recent comment 2019-09-12 21:37:10
Drying Oils Paint Mediums Solvents and Thinners

​Dear Mitra Conservators,

I would like to know the chemical formula of linseed oil, stand oil, distilled turpentine, spike oil, and dammar varnish but I have found it difficult to find this information.  Can someone provide this information for me or recommend a source ?

Best regards and thank you for the service your provide to artists,

Hector Hernandez

Varnishing Metalpoing

Question asked 2019-09-12 14:34:21 ... Most recent comment 2019-09-12 15:13:16
Varnishes Drawing Materials

I'm working on a mixed media metalpoint.  I'm using gold, copper, brass, bronze, silver and bismuth nibs to represent the hues of an oriole I'm depicting.  I do not want the base metals to tarnish; additionally, I'm framing the work without glazing.  For both those reasons I'll be varnishing the piece, with either a very thinned layer of platina shellac (the benefits & drawbacks of which we've gone over on the forum, so I won't belabor that issue) or B-72 (I know, a better choice, but I don't like how "plasticy" it feels/looks), then following either isolating layer with an application of wax medium.  Will this be sufficient to seal off the image and inhibit tarnishing?


Koo Schadler

Cutting Absorbency of Traditional Gesso

Question asked 2019-09-12 07:37:23 ... Most recent comment 2019-09-12 14:26:12
Grounds / Priming

When painting oil on top of a traditional chalk & glue ground, to cut the absorbency I generally recommend first applying a thin layer of shellac or rabbit skin glue on the gesso.  Any other recommendations?


Koo Schadler  

Incising into a Ground Layer?

Question asked 2019-09-05 22:14:30 ... Most recent comment 2019-09-09 16:40:33
Acrylic Grounds / Priming Oil Paint

​Hello MITRA folks. Can you suggest an acrylic product that could be used as a ground layer thick enough to draw lines into with a rubber tip and when dry (on panel) can be safely painted over with oil paint? (And how long would the 'open' time be?) Before the research about Zinc came out, I was happily doing this with pale Zinc blends, and then painting into the lines and overall with oil paint. A look I really loved, but lost of few to delamination, and now I understand why... Thank you for any suggestions!

Pumice powder mixed into oil paint

Question asked 2019-09-07 16:08:30 ... Most recent comment 2019-09-09 16:00:11
Oil Paint

​In my search for the best oil medium for thinning oil paint to the extreme without being up overly glossy, I came across a thread that suggested using pumice powder for a matte appearance. This sounds intriguing because my aim is to paint mountainous scenes by first pouring the paint and letting things happen as they do and then working into those poured layers. Some might say to use acyrlis for this type of approach but i'd rather start to explore other ways of getting an alcohol ink type look on the canvas.

Varnishing acrylic and oil paintings

Question asked 2019-09-04 13:45:24 ... Most recent comment 2019-09-05 22:59:56

I have a few questions about varnishing that I would like to clarify:

  1. Some manufacturers claim their acrylic​ mediums to be usable as varnishes as well. I assume that the water-based ones won't work on oil paintings, but can they really be used for acrylic paintings?
  2. Some acrylic varnishes are solvent-based (mineral spirits, etc), and it seems those are the ones compatible with oil paintings. However, are there any advantages to using them on acrylic paintings? Some claim to provide UV protection, but is this relevant and (generally) of higher degree than water-based mediums used as varnishes?

Paint integrity - Medium

Question asked 2019-08-23 13:38:02 ... Most recent comment 2019-08-30 05:45:15
Oil Paint Pigments

​I have a very limited palette. Michael Harding Cremnitz White, Robert Doaks Smalt Blue, Terra Rosa and Lead Tin Yellow GE, Old Holland Warm Sepia Extra and Mars Black. I do have Doaks Gen Ivory as an option. 

Two questions:

I was reading last night on your site that there is a problem with Smalt. I've been using it since 2004 with no problems fully realizing that is just a speck of time. Would it be a good idea to replace mine, if so any suggestions?

I had been using a tiny amount of Mineral Spirits in the past if need_1JG6973_F.jpg. If I need a bit more loose paint would Cold Pressed Linseed Oil be the safest thing to use?

The surface of my canvas has very little paint. I'm including a small work to see. I no longer use medium in my paintings since 2005. At that time I was using Blockx Amber with a little Cold Pressed Linseed Oil and Mineral Spirits. I started using that medium in 1993 again, the paintings look as when they were initially painted but I do realize that is not nearly a substantial amount of time to discern any problems.

Sinking in of umbers

Question asked 2019-08-28 02:11:23 ... Most recent comment 2019-08-28 19:12:52
Oil Paint


just read your document on FAQ's etc, in regard to sinking in of the umbers, apparently because of their clay content (PBr7 from natural iron oxide ore).

(1) I have just noted that W & N make a similar colour, synthetic iron oxide PR101 (transparent brown oxide) which has, apparently, micronised pigment particles which I doubt would contain any organic substances such as the problematic clay referred to above? If I use the latter should I then avoid the sinking in associated with PBr7? (all other things being equal);

(2) If I use an oil-based primed canvas such as lead white (instead of an acrylic gessoed one) would this stop the sinking in, even if I use PBr7? 

Many thanks in advance

Resource of Oil Painting Best Practices

Question asked 2019-08-23 17:53:09 ... Most recent comment 2019-08-27 17:46:50
Oil Paint Solvents and Thinners Studio Tools and Tips Paint Mediums

Can anyone recommend a book, article or website that would teach me the best practices for creating a structurally sound oil painting, especially in layers? I read so much conflicting information on fat over lean, and the use of mediums. I am experimenting with water mixable oils, but I figure that a resource on traditional oils would be helpful if I replace "solvent" with "water." Many thanks.​

Coroplast acid free versus regular

Question asked 2019-08-23 12:33:46 ... Most recent comment 2019-08-26 16:34:52
Matting, Framing, and Glazing Industrial and Non-Traditional Products Other Rigid Supports

I am considering using Coroplast as a support for large (48 x 48) drawings  on archival Tyvek. My main question is whether I need to use acid free or if standard white coroplast is neutral an inert. See more details below.

I have an exhibition coming up very soon that I need to prepare for. My original solution was to use acid free foamcore but its arriving with dented edges so I am exploring alternative more durable materials.

I will use acid free tape to adhere the drawings​ to what ever support I will use. There will not be a frame, but the work will be protected by a sheet of plexiglass that will be spaced away from the work. L screws will mount the work to the wall with custom spacers to separate glazing from the drawings.

In some research online I came across a discussion stating that there is no difference in acidity between the acid free coroplast and colored coroplast that is not acid free (white or clear is what I would prefer). It may be easier to find the regular coroplast locally in the large sheets that I need which is why I am asking if there is a significant difference. I may be able to line the support with an extra sheet of Tyvek as a barrier if that would be necessary.

thanks very much!

Overpainting eco-solvent inks

Question asked 2019-08-23 02:30:22 ... Most recent comment 2019-08-26 12:03:12
Ink Oil Paint Paint Mediums Industrial and Non-Traditional Products Dyes Grounds / Priming Solvents and Thinners Sizes and Adhesives Pigments

​I wish to overpaint in oils a canvas with an existing image in eco-solvent ink. Is there a bonding spray that would permit this? 

Egg tempera varnishing

Question asked 2019-08-25 06:40:40 ... Most recent comment 2019-08-26 11:59:10
Egg Tempera

​I am fairly new to your forum and I am not sure whether is fine to ask a question already placed some time ago.

I am currently at my final year of my Icon painting studies in Russia and I will soon be faced with this dilemma of varnishing. Here at our school they have taught us to varnish using Olifa,boiled linseed oil. This method works well in Russia due to their weather conditions but in my country Cyprus, Olifa tends not to dry and remains sticky. It also doesn't provide enough protection. Apart from that it ruins the warm and cold relationships upon which the icons are built on. Some people tried using Olifa mixed with boat varnish to make the final film stronger. Others just place Olifa for 5 hours remove it, wait for the icon to dry and varnish with an acrylic varnish. This provides some protection from the solvents in the varnish and ensures even spreading of the varnish. I have tried replacing Olifa with Poppy oil that doesn't change the colors and then place the varnish on top. This still is not ideal since this oil as well doesn't seem to dry in my country's  conditions.

I have read your suggestions about PVA ethanol or acetone based followed by varnishing. This is the first time I read about it and I have some questions.

1. Will it be fine to use this method on a freshly painted icon? Wont the acetone or ethanol react with the egg since they are organic solvents? People don't understand that an icon needs to cure before varnishing.

2. Will the isolation layer be even since no oil is present to saturate the ET layer?

3.Does this method provide sufficient protection? People tend to care for icons but not in a proper way which sometimes destroys them

4. Does this method has any effects on naturally occurring pigments such as cinnabar, lapis lazuli, carmine?

Thank you


More questions on 'painting into wet oil paint'

Question asked 2019-08-25 22:36:29 ... Most recent comment 2019-08-26 11:51:47
Oil Paint

​Hi all,

This question possibly should have have put thru the 'post user comment' function on a previous post of mine dated 2019.8.06, titled: Painting into wet oil paint., but I don't know if it would have been spotted and answered, so I have put it here. Appreciate your advice on what is the best way to go about this.

Anyway, after carefully re-reading the moderator comments I still have a little doubt concerning my latest portrait project and would appreciate your advice again:

About 2 weeks ago I did a very thin underpainting in traditional oils straight from the tube, onto an acrylic gesso primed canvas (only professional quality name-brand oils/canvas used. As the canvas was triple-primed by the manufacturer I did not add any more gesso). No solvents or mediums. When I touch it, it is very slightly tacky and rubbing a tissue on the painted area (burnt sienna PB7/PR101) produced a very slight stain on the paper. Both these effects were only very slight.

I have been painting for some years and in the past have used an OMS thinned wash for initial underpainting, which dries fairly quickly. I am trying to avoid using solvents now, just paste paint.

I have tried the 'fingernail indent' test but the paint is so thin that I couldn't make much of this test.

Should I wait until the painting is completely dry to the touch before applying a further layer? I have never been so exacting before, but now are producing paintings for others so want to avoid any issues down the track. 

Many thanks again

Lavender spike oil as a solvent/thinner

Question asked 2019-08-21 16:58:09 ... Most recent comment 2019-08-23 19:07:35
Solvents and Thinners


I added this onto the tail end of another discussion but probably should have started a new question, so here goes:

I note that in this discussion it was said that.. using large amounts of an essential oil is detrimental. Is using Lavender spike oil: tube oil paint in 1:1 or even up to 2:1 (max.) OK?

I.E. what is the dilution limit you can use in an underpainting and still achieve adequate adhesion?

Recently reading an article from Jerry's artarama re this oil indicates that the vapours are non-toxic and it evaporates about the same speed as OMS, can be mixed with mediums, and a safe alternative to OMS. (no special ventilation requirements). My understanding of the MSDS also gives no concerns unless you swallow it or get it in your eyes. The only drawback seems to be the high price as compared to OMS.

Many thanks in advance

Sizing Handmade Papers

Question asked 2019-08-21 10:15:45 ... Most recent comment 2019-08-23 18:21:20
Gouache Ink Sizes and Adhesives Watercolor

​What would be my options for sizing an absorbent handmade paper (i.e. a Japanese paper) for a subsequent ink, watercolor and gouache painting? It would be framed under glass or plexi when finished, of course. Thanks for your thoughts, MITRA folks!

Paint integrity - Medium

Question asked 2019-08-23 13:30:57 ... Most recent comment 2019-08-23 13:00:00
Oil Paint Pigments

No gamsol but still fat over lean process

Question asked 2016-11-28 16:18:20 ... Most recent comment 2019-08-20 19:29:18
Drying Oils Environment Oil Paint Paint Mediums Solvents and Thinners
Has any one of you experience with Lavender spike oil or Zest-it products to replace gamsol in the beginning of the painting process? I would like to work with more environment and health friendly products. Normally I use gamsol for the transparant wash and mix gamsol and lineseed for Amber underpainting. Lineseedoil in my first layer of full paint and stand oil in second layer. Than when finished a varnish. So if I start with a spike oil (which maybe does not give a stable paint layer) from the beginning in the first 2 steps, I need varnish in my second paint layer which Is not preferable. So how do I get a wash and underpainting transparant but still working or adapting all the fat over lean steps?

Thinning oil paints with solvents

Question asked 2019-08-19 19:05:24 ... Most recent comment 2019-08-20 19:09:57
Oil Paint

​RE: how much can you thin down tube paints without encountering adhesion problems? I have frequently read that the maximum dilution of solvent: oil paint is somewhere between 1:1 to 2:1. Any more than this will leave the paint film underbound, i.e. not enough oil binder to stick the pigment to the canvas. But recently I read/heard somewhere that it doesn't matter anyway provided you paint over this immediately with paint layers with much less solvent as subsequent layers would contain enough binder to provide adequate adhesion. I have watched numerous YouTube videos of professional artists using really watery washes (the wash runs down the canvas) to either tone the canvas or lay-in a drawing. I have seen this so many times (an in art classes) that if it was such a detrimental practice to the longevity of the final painting surely they would have changed their practices by now. After all, if you are doing paid portrait commissions and a few years later they fail in some way then that would be disasterous for business. How do they get away with flouting the common sense 'rules', or doesn't it really matter provided you paint immediately into this watery wash with thicker paint?

Would love to hear some definitive statement on this.

Many thanks

Filling in the weave of a canvas

Question asked 2019-08-19 18:44:38 ... Most recent comment 2019-08-20 18:39:07
Grounds / Priming


with regards to using a canvas with a medium textured weave (or any but the finest weave for that matter) I have recently read that it is best to even out the surface with extra acrylic gesso so that the "ground equalizes  the surface of the support." .........."this would involve losing the grain or texture of the canvas, so that oil paint layers applied over the painting ground like down flat and evenly." (P295 Pip Seymour, The Artist's Handbook, 2003.) I have often wondered about that, but this is the first time I have seen it in print from a seemingly reputable source.

I would prefer to skip this extra gessoing if possible, but is it best practice to follow Seymour's advice? It does seem technically logical what he says.

Appreciate your expert input,

Many thanks

Ampersand gessobord panels

Question asked 2019-08-15 23:03:49 ... Most recent comment 2019-08-18 22:49:31
Rigid Supports


Over the years I have used a number of surfaces for painting with traditional oils, including stretching my own canvases, etc. I am over this now and just want to paint using commercially prepared surfaces. I dislike the 'give' when you are painting on stretched  canvas and will probably concentrate on rigid panels. The only quality commercially prepared panel I could find is Ampersand gessobord which, they claim, has 2 layers of 'seal' between the panel and acrylic gesso primer and support-induced discolouration will not occur. They state the only substance left in the panel during manufacture is natural lignin (glue). I have recently painted on a small sample panel and then tried to scrape the paint away from the gesso without any success. I then tried to dig into the panel to try and seperate the gesso but no go. The panel itself does not crumble and the whole thing appears sturdy, at least to my basic testing. Ampersand claim they are archival and will last over 200 years. state that rigid supports are more archival than flexible ones (Canvas, linen). 

I have no association with Ampersand except as a customer. I have more recently begun a portrait in oils on a larger gessobord. I did an underpainting with thinned watercolour (according to this is fine provided the layer is thin and you let it dry properly. They also say it can be re-worked by simply wetting it) which means I can avoid solvents altogether, hence my reason for using a gessoed panel. I don't want to use panels with canvas stuck on them as youy don't know if SID will occur and the textile can still move anyway due to temperature and humidity changes. Where I live it can get over 40 deg. Cel in summer at times.

I know that Ampersand make other panels, but I want one ready to paint on and with the Archival seal, hence Gessoboard. They only disadvantage is that the larger panels have to be in a cradle which is quite expensive. The smaller ones need to be framed, which has to be factored in, cost-wise. For less important works I would just go back to stretched canvases. I use cheap canvas panels for quick studies.

Am I on the right track? Are Ampersand gessobords really a quality archival surface? I really want to find a good quality pre-prepared gessoed panel and hope these Ampersand ones fit the bill.

Appreciate your comments,


Painting over a 10 year-old underpainting

Question asked 2019-08-15 02:38:56 ... Most recent comment 2019-08-16 16:50:35
Oil Paint

​Hi all,

I did an underpainting (self portrait) about 10 years ago. It was one initial thin layer either scrubed in tube paint or with a bit of OMS added. I think it possibly was the former as some areas have a slight sheen, but most of it is matte. I would have used the same process across the entire canvas, not with OMS in some areas and scrubed-in paste paint in others. I was reasonably accurate as far as drawing goes but no details. I didn't use OMS much then, as now.

For some reason I put this aside to dry and couldn't get the drive to re-start it due to a lengthy illness in the family, then eventually forgot about it. I am almost certain it was W & N acrylic gesso triple primed. It is a stretched canvas and there is no indication of paint/oil penetration to the rear of the canvas. It is life-size from top of a cap to below belt and I am reluctant to throw it away as it was part of my art journey at that time. The canvas probably needs tightening a bit.

I have read some of the discussions here about pentimenti; scraping, sanding and wiping with OMS and would appreciate your comments on my proposed method: 

(1) Clean the whole canvas with OMS on a lint-free cloth. Let this dry. (2) As there are  no raised areas/impasto, or indeed any surface imperfections, I would then sand it lightly to give a uniform matte surface. Taking care not to damage the acrylic gesso. Clean any particles off completely and (3) wipe it down again with OMS. Let this dry, then (4) apply a thin layer of titanium white. (5) Let this dry (fingernail indent test) then start painting in thin layers of paste paint straight from tube until I get to the desired finish.

Probably I should start a new painting but I want to re-use this existing canvas. If one day it 'fails' then that's fate I suppose. 

Many thanks in advance.

Painting over an existing portion of a painting

Question asked 2019-08-05 10:58:48 ... Most recent comment 2019-08-14 20:00:16
Oil Paint Grounds / Priming

​I have a painting that was completed in February. It is oil on a ground of Golden White Acrylic Gesso on a cotton support with wood stretchers. Paint straight from the tube, Old Holland. Occassionaly wash a brush out in Gamsol but blot on a rag to remove the liquid. I paint very thin, this particular portion may have one or two coats primariliy made of greys, some red in other areas. I believe it was Titanium White, Mars Black and Cad Red Purple. A tiny touch of Old Holland Cyan Blue in someof the Greys.IMG_0866.jpg The texture of the canvas is easily seen and felt. I would like to replace that portion with a Union 76 Ball. This gives you the idea of color I will be dealing with. I have ideas of how to do this, but I would prefer to ask you as I have never done this before and want to do it the best way for archival purposes. 

I appreciate any and all help and am happy to supply any additional information necessary.

Removing water stains from oil on linen painting in progress

Question asked 2019-07-17 01:47:35 ... Most recent comment 2019-08-14 19:52:34
Oil Paint Flexible Supports Solvents and Thinners Other

​Dear MITRA,

I am about to resume work on a large format oil on linen diptych after it had to be placed on the back burner for a few years.  At my previous studio, I had some mysterious leaks or perhaps a humidity condensation issue that periodically dripped a pale, thin brown liquid from various areas of the ceiling. After moving to a different space, I discovered that some of this liquid had apparently hit the floor in front of one of these large oils, and then splashed back up onto the lower area of the painting. Luckily the drops were so small that the linen was not damaged, but a series of small water stains/rings were left behind. I tried to gently clean them off with a touch of distilled water, but that wasn't strong enough. OMS worked better, but once the OMS evaporated, you could still see a fainter trace of the whitish-looking rings. Should I try artists' rectified turpentine, then wipe away the turps residue with OMS? If any micro-pores were opened up in the paint as a result of using the stronger solvent, it might increase adhesion anyway since the paintings have been waiting for so long for me to complete them. Please let me know how you think I should best proceed.

If it matters, I am using oils made with walnut oil, and initially used a solvent-based alkyd medium, then a walnut/alkyd. 

Thanks very much!

Rembrandt's paintings question

Question asked 2019-08-13 15:27:24 ... Most recent comment 2019-08-14 19:41:19
Art Conservation Topics Oil Paint Scientific Analysis Technical Art History

​The Rembrandt paintings I have seen in the National Gallery in London (and others online) have a strong dominant yellow-brown hue range. Is this just down to the pigments used and his palette preferences, or is some of this the result of yellowing varnish?

Using natural soil pigments on paper?

Question asked 2019-01-24 06:06:43 ... Most recent comment 2019-08-14 19:00:36
Paint Making Watercolor Pigments

​Dear MITRA Moderators, 

I want to create a three-layered paper piece based on the element of Earth. I'm doing a four-piece suite, one for each element, and am involving each element directly (for fire, I burned the edges of the paper), etc.

I'm using a 300 lb paper for the first layer, and would like to use natural pigments including clay soil. I'll adhere a second layer (140lb paper) to the first with a brayer, using a product recommended to me by the art supply representative (Daniel Smith Transparent Watercolor Ground). I'd like to use natural pigments here, including clay soil and a homemade walnut stain. For the final paper layer, I'll adhere a thinner paper (I think it's 90 lb) and use watercolor pencils. I plan to distress the first and second paper layers respectively to expose the pigment underneath.

Does this sound like a sound approach? Can you use regular clay from a yard or creek? Is homemade walnut stain ok to use, or would it be too acidic, etc? 

Many thanks! I'm really excited about this project!

Martin F. Weber "Cleaning Solution for Oil Paintings

Question asked 2019-08-12 08:50:58 ... Most recent comment 2019-08-13 19:30:00
Art Conservation Topics

Hello all.

I am looking for any information about this product.  It has been discontinued by Weber and there is very little information provided by the manufacturer.  Online searches for data about it and its intended use is also not popping up.  Does anyone have information they care to share?


Mike Townsend

Fix Charcoal Underdrawings

Question asked 2019-08-11 18:26:07 ... Most recent comment 2019-08-11 22:23:41
Oil Paint Drawing Materials


I’m working with compressed charcoal #2B, #4B and #6B underdrawing on linen canvas and Williamsburg Lead Oil Ground. I would like to control where the charcoal mixes with the lead linseed oil underpainting.

I’ve read two articles on Just Paint hoping I might find a solution but in both cases they don’t recommend using MSA or a retouching varnish.

1) Why Oil Painting Over MSA or Archival Varnish Is Not Recommended

2) Oiling Out and the Cause of Dead Spots in Oil Paintings

I’m considering two options: 

1) Use Williamsburg Alkyd Resin, cut with Turpentine or Gamsol 1:1 or 1:2 and spray a thin layer over the charcoal drawing before applying the lead oil paint.

2) I’ve tested this formula: linseed oil, damar resin (5-pound cut)  and turpentine (1:1:3), and after waiting 1-3 hours, I applied the lead oil paint. This test did not to work very well since the thin retouching varnish layer disolved when I applied the lead oil paint.

I would appreciate any feedback about the two options mentioned and an alternaitive approach.

Thanks so much,


Re: clarification on "Confusing concepts in oil painting...etc"

Question asked 2019-08-06 19:52:16 ... Most recent comment 2019-08-08 02:27:55
Oil Paint


fascinated by this discussion re abandoning the fat-over-lean and thick-over-thin that we have been taught. From the comments made about 'glazing' i.e. just use paint straight out of the tube ( = paste paint) and with a stiff brush apply it thinly, it would seem that you can paint each layer thinly, even the final one.

Appreciate your advice on what I wish to do in constructing a non-toxic painting (no solvents): (1) for the initial layer I do a block-in drawing with e.g. burnt sienna. This layer is quite thin and I 'tonk it out' (i.e. put absorbent paper towel on top and rub most of the paint off). I am left with a thin layer. This would approximate the idea of an initial layer using a solvent/oil wash. I think the oil in subsequent layers should be able to penetrate this and bind to the canvas.

(2) When doing indirect painting, for subsequent layers I will apply paste paint thinly (as per your advice), allowing each layer to go touch dry before applying the next, until I reach my final degree of finish. i.e. EACH LAYER is paste paint applied thinly. I plan not to use any added oil or medium because I dislike the slipperiness that this causes. From your original article these additions appear unnescessary anyway.

Appreciate your feedback

Painting into wet oil paint

Question asked 2019-08-06 20:33:10 ... Most recent comment 2019-08-08 02:14:39
Oil Paint


when doing indirect oil painting how long should you wait before you apply the next layer? (using paste paint straight from the tube, unaltered in any way). From my understanding of artists comments it would seem commonplace for them to e.g. start a painting in the morning; then have a lunch break, then return to the painting to add further layers in the afternoon. I have also heard that some artists will overpaint the following day(s) because the iniitial painting is still wet. Stating that this slow drying was one of the advantages of oil paint in that you could continue to work on the same painting day-after-day.

From one of the articles on this forum it discusses how oil paints dry through a process of oxidative polymerization i.e. oxygen permeates the oil paint and starts the long, slow process of cross-linking of the binder molecules until a solid eventuates. Subsequent layers slow the ingress of oxygen down into the underlying layers but don't stop it. This process is faster at the start, then slows down apparently. 

If I was to apply additional paint to a partially dried layer does this have any detrimental effect on the polymerization of underlying layers? For example, in the case stated above where I return to a partially dried painting the same day, or the following day(s), will I do permanent damage? Or will it have no negative effect on the painting as a whole? It seems such a common practice.

I realize that enviromental factors come into play in that in hotter weather the paint will dry faster than in mid-winter. But I have never heard this being a factor in relation to the above scenario.

Another reason for my question is that in our summer time it can get really hot, well into the 30 degrees ,or higher, and the paint will start to tack up a little bit even after just a couple of hours. Should I stop then and let it go touch-dry, or OK to keep painting?

Appreciate your advice

Pyrrole Red

Question asked 2019-08-06 10:12:52 ... Most recent comment 2019-08-06 19:06:25

​I'm working with a new pigment, Pyrrole Red PR 254.  It resists wetting, so I added a bit of alcohol to disperse and convert it to a paste.  Usually once a pigment has successulfy dispersed in water, and it dries out, adding more water readily rewets it.  However when the Pyrrole paste dried out, adding more water didn't reconvert it to a paste; I had to add more alcohol.  I'm interested in this, as well as any other comments on Pyrrole Red, which is new to me.

Thanks, Koo Schadler

Confusing Concepts in Oil Painting: Fat over Lean... Thick Over Thin... Thick Over Lean... Whatever... Let's Get Rid of Them.

Question asked 2019-08-01 01:19:37 ... Most recent comment 2019-08-04 14:21:20
Oil Paint

Let's toss out the concepts of “fat over lean” and for that matter “thick over thin” (or the confused “thick over lean”) while we are at it, and let's consider the physical structure of the paint.

To help you to understand the properties of oil paint, it is helpful to understand the relation between the pigment and oil. One way to think about the relationship between pigment and binder is a brick wall. Every mason knows there is an ideal ratio of mortar to brick. Too much mortar and the wall is weak. Not enough mortar and the bricks fall apart.The same relationship exists between the pigments and binder in dried paint. We call this relationship or ratio the pigment volume concentration or PVC. Pigment volume concentration (PVC) is the volume of pigment compared to the volume of all solids. If paint has a PVC of 30, than 30% of the total binder/pigment is pigment and 70% is binder solids.

The point at which there is just enough binder to wet pigment particles is called the critical pigment volume concentration (CPVC). For almost all colors this is between 45% and 55% PVC. Films with lower concentrations of pigment have more gloss but as the PVC increases they become increasingly matte. Films with high percentages of pigment are more permeable to moisture and susceptible to solvents. This is because with more pigment, there is less binder to fill the voids between pigment particles. This porosity leaves the film open to the environment. Films with higher pigmentation have increasingly lower tensile strength.

Most paint in tubes contain enough binder to wet and envelope pigment particles and so are at about the critical pigment volume concentration for that color. The variation in the pigment volume of particular colors between brands are due to the type of oil used, the amount of oil (some paint makers may choose to make their colors softer or thicker) and the amount of additives.

So the best way to discuss paint is by understanding this relation between the pigment and oil which is expressed as the pigment volume concentration (PVC). Oil paint(straight out of the tube is in the form of a paste and is usually at its CPVC. Adding oil lowers the PVC of oil paint, while adding solvent potentially increases the PVC (high PVC). Hence the ideal paint is a paste paint and this is why the admonition to “apply thick paint thinly” or work with paste paint in thin layers, is the optimum way of using oil paint.

From this it is clear that paint consists of both liquid and solid components. In the case of oil paint, the liquid component is a drying vegetable oil. The oil undergoes chemical and physical processes that change it from a liquid to a solid, which process is called “oxidative polymerization”. Oil is the binder or glue that holds the pigment particles (solids) together and adhered to a substrate.

When it comes to adhesion oil is the glue. While many artists believe that mechanical adhesion is most important when it comes to adhesion of paint to a substrate, what is more important is “dispersive adhesion”, which does not rely on absorption into a substrate or surface texture (although the latter improves dispersive adhesion) but rather on surface energy and polarity. Hence, paste paint adheres better than paint that has been heavily diluted with solvent (high PVC) even if it is partially absorbed into the substrate, because it has less oil or binder to adhere to the surface of the substrate.

Requesting Explanation on posting: Confusing Concepts in Oil Painting....

Question asked 2019-08-03 11:22:33 ... Most recent comment 2019-08-03 19:18:53
Oil Paint

Thanks for that great explanation on PVC for oils! I have 4 follow up questions -  If we are to use the correct PVC for our oil paintings and adhere to the "paste paint adheres better" approach, then does this (1) eliminate the initial thinned out under painting stage or use of a light colored undertone for the canvas? (2) eliminate the oiling out between paint layers? (3) are we better off by eliminating any additional Alkyd mediums to help make the oil paints more fluid? (4) and lastly, how would our applications of a "glazing" layer for special effects, be adjusted to keep everything in a PVE balance?


Amount of zinc in titanium white oil paints - some information

Question asked 2018-03-09 14:17:46 ... Most recent comment 2019-07-28 22:20:22
Pigments Scientific Analysis Oil Paint

​Hi all,

I've emailed several art manufacturers that I use here in the UK regarding the amount of zinc in their titanium white oil paint.

Here are the results which may prove useful to you all:

CompanyProportion of Zinc
Winsor & Newton - Artist Oils"There is not enough to cause a brittle film--less than 2%."
Royal Talens - Rembrandt"The percentage of zinc oxide for both products is between 5% and 10% … They both contain the same amount of Zinc. The Safflower oil makes sure it’s getting less yellow."
Schminke - Norma"we can say that our #11114 titanium white have a content of PW4 lower than 10%."
M Graham - Oil Color"I have been told that we use under 3% Zinc in our Titanium. We do have a zinc free oil 11-181 that I can recommend if there is a concern."
Jacksons - Artist and Professional Oil RangeWon't reply after 2 mails
Blockx"Paint made with Titanium Dioxide pigment is very hard and misses elasticity. So, we do add indeed a very little Zinc pigment. But the proportion is of course secret. And will defer from one manufacturer to another. " - Won't reply after 2 more chasing emails
M Harding"It's about 10% of the overall volume."
Williamsburg"We are happy to report that we do not use any zinc in our Titanium White oil paint." - 0%
SennelierWon't reply after 2 mails
Maimeri - ClassicoWe can declare that the proportion of Zinc in Classico Titanium White 018 is moreless 50%."

Polyester/cellulose mix paper

Question asked 2019-07-24 11:52:07 ... Most recent comment 2019-07-27 14:39:09
Drawing Materials Flexible Supports Industrial and Non-Traditional Products

I have recently found blank rolls of wallpaper (160+ gsm), sold as a home decoration solution. They're made from a mix of polyester and cellulose fibers, and I was wondering about the feasibility of using that paper as a drawing/painting surface. Given the better aging properties of synthetic fibers, would the added polyester content increase the longevity of such paper, compared to pure cellulose papers? ​


Question asked 2019-07-26 14:34:28 ... Most recent comment 2019-07-26 22:27:01
Grounds / Priming

​Caparol ( a german product ) is very useful for grounds ( mixed witjh chalk and lithopone )Is it available in America, somewhere?

Indian ink pitt pen drawing painted over with gouache

Question asked 2019-07-24 15:39:31 ... Most recent comment 2019-07-24 18:59:01
Gouache Ink Pen

​Hello dear people from Mitra!

I have a question about mixing materials.

I have asked already about compatibily of indian ink and gouache, and i know it is compatible and mixable, since i had answers from good people from your forum and i saw many old master artworks that were made precisely with these two techniques.

What worries me is, that i have used Indian Ink pitt pen and i did full ink drawing, with deep crosshathing and deep darks, so i did a lot lines with it. 

This was done on thick watercolor paper.

And i really wasnt happy with the end result, but saw the potential in the work, so i reworked or painted over the whole drawing with artists quality gouache (using black and white only).

The works looks good now, but i am intersted is it ok that i did this?Will my work be ok?

And if there are no mistakes visible now, and the work is one week old, does that mean that everything will be ok in future?

Thank you

Marko Karadjinovic

1st MURAL Opportunity- Questions on how to get started

Question asked 2019-06-29 11:28:19 ... Most recent comment 2019-07-22 20:16:13
Acrylic Mural Painting Handling and Transportation Rigid Supports Paint Making Pigments Grounds / Priming

Hello, I was wondering if someone might be able to help me.

I actually have 2 mural opportunities, but right now I'm trying to focus more on one over the other because it seems more 'involved.'

One piece is to be mounted outdoors.  The other piece is to be placed over doors- that is to say, I believe the intention is that it be painted directly on them.  I do not know the door material or their dimension- nor the dimensions of the outdoor mural- but I do know the doors will have to function.  The mural-side of the door is at the interior of the building, the other side is to the exterior, like a garage door. It's a metal roll-up door.


I need to figure out exactly what I need to spend in order to complete each project.

I currently have:

  • Red Oak Plywood- Six 36in*36.5in pc.'s & 15 1Ft. sq. pc.'s all 3/4in. Thick
  • 10pack mini rollers for smooth-semi smooth surfaces - what should I use rollers for vs. brushes? Do I clean to re-use them or are they a single-use type of product?
  • 76mm angled Poly-blend bristle brush, for smooth & semi-smooth surfaces
  • 10 kit HDX Nitrile Disposable Gloves- 'not for use w/ chemicals'
    • Will these work w/ Varathane, GOLDEN Isolation Coat, & Primer?
  • KILZ 2 Latex Primer/sealer/stainblocker Multisurface (Drywall, masonry, galvanized, & more*) Interior/Exterior Water-based- re-coat in 1hour
  • Varathane Brand Ultimate SPAR URETHANE?, Oil-based, clear gloss- Recommends 3 coats & min 4hours dry time(sanding only if drying for 12+ hours) ==> notes cancer & reproductive harm as well as the need for adequate ventilation, but also the harm go humidity
    • Can I use this product outside?- where should I let it dry?

It has been recommended that I get:

  • sand paper. 200 grit- I would be hand sanding to remove splinters - specif. @ he edges where the wood was cut, but I'm assuming I'd have to do the entire board for the primer to adhere - so I'm wondering if there's a correct way to do this...

I think I need:

  • Goggles
  • Respirator
  • Coveralls 
  • Knee Pads
  • Mixing & Storage Containers
  • 1gal. Heavy Body Acrylic Paint-,at least 6 colors- including neutrals? (white, black, brown)
  • 1 Gal. Isolation Coat
  • 1 Gal. Solvent- for the Varathane?, I don't know the exact details of this product, but when I looked up polyurethane, it req.'d a solvent to be used
  • Mounting Hardware
  • Probably additional Painters Tape & Brushes

All 'clothing items' are for the Varnish & finish products- everything appears to be highly toxic, don't know if there are safer alternatives.

All amts were 'guess-timated' before the addition of the 2nd mural piece and it's different setting.


I am still trying to come up with some sketches to determine the overall composition, but I am wondering:

  • How can I go about choosing colors?- The room is full of very 'non-modern?' colors, very little blues, purples, or even oranges and the colors are very muddy and dark.  I would like to choose a period-appropriate color scheme but still add some brightness to the colors I choose and some naturalistic purples and blues that go with the theme of the piece.  I want to make sure I have a large variety of colors, but not purchase unnecessary colors I could just take the time to measure out and mix.
    • Example- If I have a largely white background, fo I need to purchase white paint, or can I just use the Primer? Do I tint the Primer to make other neutrals or do i need to use paint
  • How can I go about estimating and pre-mixing any batches of specific colors to work with?
  • Is it possible to follow and early-1900s 'recipe' for specific colors and get a somewhat accurate result using paints purchased today?

I'm thinking the wood panels would be used for the outdoor piece that would be on the side of a house and would not move.

Some or all of these panels may also need to be shipped... I'm thinking some of the smaller panels could be used to flank the large doors.  The large panels may have to be shipped with some kind of mounting instructions.

I currently trying to read through various MITRA posts, but these are the more pointed inquiries I can think of for myself...

Thank You

Old Holland Zinc white

Question asked 2019-07-20 19:05:21 ... Most recent comment 2019-07-21 21:47:30
Oil Paint

​The Old Holland safety data sheet for their zinc white oil paint lists alongside 70-90% zinc oxide.   3-5% titanium dioxide.  Which strikes me as an interestingly odd thing to do.  Would there be any advantage to adding such a small amount of titanium white to an otherwise pure zinc white paint?


Need for sealing under oil grounds over acrylic primer on hardboard?

Question asked 2019-07-20 12:26:50 ... Most recent comment 2019-07-20 20:45:10
Grounds / Priming

​Dear Moderators Please excuse my "test" question posted prior to this one. I've been having a lot of trouble with the question form. This is the 3rd time I've tried to post this question. I have primed a number of unsealed hardboard panels with 3 coats of acrylic primer and plan to follow up with 2 coats of lead primer. Should I have sealed the panels first eg with a PVA or acrylic resin emulsion? Looking forward to your responses. Kind regards, Jenny


Question asked 2019-07-20 12:21:08 ... Most recent comment 2019-07-20 12:20:00
Grounds / Priming


Sealing Graphite under Oil Paints

Question asked 2019-07-19 12:59:16 ... Most recent comment 2019-07-19 16:21:14
Oil Paint Other Paint Mediums Pencil Drawing Materials Ink Pen Studio Tools and Tips

​Hello MITRA folks...I would like to seal a graphite or India Ink line drawing on canvas or board that has been 'gessoed' with acrylic dispersion fluid. The drawing would then be painted over with oil paints, but some of the drawing linework may remain exposed in the final painting. I would like to know what my options are for sealing the linework that would be 'durable' if left exposed in the final, varnished image, but also a good bond with the subsequent oil paint in some areas. I'm thinking acrylic matte medium, but maybe there are other options...? Thank you for your thoughts!

Shaping brushes after washing.

Question asked 2019-07-07 20:15:27 ... Most recent comment 2019-07-16 22:28:29
Oil Paint Paint Additives Studio Tools and Tips

​As stated, I want to be able to wash brushes with soap and water, shape them with the help of some product, and use them in the morning without having to rinse them in sovent.
Candidate products so far are saliva, gum arabic, egg white, and maybe milk. I'm leaning toward gum arabic.

My question is, will any of these unduly affect the paint film if it is not washed out of the brush before using?

Ron Francis.

Traditional Gesso

Question asked 2019-07-11 10:26:10 ... Most recent comment 2019-07-11 16:00:49
Grounds / Priming

When I first became a tempera painter, I experimented with many different recipies for traditional gesso (gleaned from various books – there was no on-line world back then!).  I got both good and bad results (some gessoes developed cracks).  Eventually, after much reading and experimenting to better understand the properties of traditional gesso, I arrived at what seemed a solid recipe based on ratios versus specific measurements; it's always yielded a good, reliable surface, and I've heard from many artists with whom I've shared the recipe that they too use it with success. 


I've found that a mix of 1 part glue to 16 parts water, then 1 part of this glue water combined with approx. 1.5 parts chalk or gypsum, yields a not too soft, not too hard ground.  However there is some variability in the water to glue ratio – more glue in the mix yields a harder ground, less glue a softer ground. So an artist has flexibility in the recipe depending on what sort of ground he or she wants to work on.   On the other hand, in my experience, if one strays too far outside certain parameters in the water to glue ratio, the resulting ground is either too hard (anything beyond about 1 part glue to 12 parts water = too much glue in the ground) and is prone to cracks; or too soft (anything less than about 1 part glue to 20 parts water = too little binder) and the ground becomes friable.  


Recently I read a gesso recipe from a paint tech, whose knowledge I trust and respect, which recommends a ratio of 1 part glue to 5 parts water.  I was surprised by this number; it seems way too much glue to me, and in fact I have a panel made from this recipe that dramatically cracked (see attached image). Gesso Panel cracks.jpg   However the tech feels confident that a 1 glue to 5 water ratio is reasonable for gesso, and also has panels made from this recipe that haven't cracked.  (FYI, I understand that glue is not the only reason gesso can crack – changes in temps, humidity, wood grain telegraphing through, dropping a panel on its edge, etc. also can cause cracks…)


I've always felt pretty confident of my understanding of true gesso – that too much glue in the mix is problematic, and anything beyond about 1:12 or maybe 1:10 tops is too much glue – but now I'm wondering if there is more flexibility in the ratios for true gesso than I realized.  Any thoughts? I want to make sure I'm understanding gesso correctly. 


Thanks,  Koo Schadler 

Which side of Dibond panel?

Question asked 2019-07-01 13:25:14 ... Most recent comment 2019-07-08 02:20:41
Rigid Supports Acrylic


I am using Dibond panels for my acrylic paintings. I usually sandpaper the polyester coating and then clean it with isopropyl alcohol before applying some acrylic gesso on top of it... Both the panel sides are covered with a poyester coating. One side is glossy, the other is mate. Can I use any of them? Or is one of them better for adhesion? Thank you.

Best regards,

Thomas Ehretsmann

Adhering canvas to plywood wood panels

Question asked 2019-07-01 20:14:53 ... Most recent comment 2019-07-01 22:12:24
Rigid Supports

​A previous post discussed using shellac to seal engineered wood panels.   (Note: I'm not yet using the pigmented shellac recommended in the post above but will for future projects)  Anyway,  I have been gluing pre-primed canvas to cradled plywood.  I use 2 coats of undiluted shellac (as the manufacturer recommends)  to seal all sides of the panel and cradle.   I then used PVA glue to adhere the canvas.  I was just wondering if there were any potential issues with this approach such as poor adhesion of the glue to the shellac or future delamination of the shellac under the canvas?  Should I be diluting the shellac to increase absorption and ensure good tooth for adhesion?  

1st MURAL Opportunity- Questions on how to get started

Question asked 2019-06-29 11:19:03 ... Most recent comment 2019-06-29 11:13:00
Mural Painting Paint Making Grounds / Priming Handling and Transportation Rigid Supports

Hello, this is Martha Rose.  I was wondering if someone might be able to help me.

I actually have 2 mural opportunities, but right now I'm trying to focus more on one over the other because it seems more 'involved.'

One piece is to be mounted outdoors.  The other piece is to be placed over doors- that is to say, I believe the intention is that it be painted directly on them.  I do not know the door material or their dimension- nor the dimensions of the outdoor mural- but I do know the doors will have to function.  The mural-side of the door is at the interior of the building, the other side is to the exterior, like a garage door. It's a metal roll-up door.


I need to figure out exactly what I need to spend in order to complete each project.

I currently have:

  • Red Oak Plywood- Six 36in*36.5in pc.'s & 15 1Ft. sq. pc.'s all 3/4in. Thick
  • 10pack mini rollers for smooth-semi smooth surfaces - what should I use rollers for vs. brushes? Do I clean to re-use them or are they a single-use type of product?
  • 76mm angled Poly-blend bristle brush, for smooth & semi-smooth surfaces
  • 10 kit HDX Nitrile Disposable Gloves- 'not for use w/ chemicals'
    • Will these work w/ Varathane, GOLDEN Isolation Coat, & Primer?
  • KILZ 2 Latex Primer/sealer/stainblocker Multisurface (Drywall, masonry, galvanized, & more*) Interior/Exterior Water-based- re-coat in 1hour
  • Varathane Brand Ultimate SPAR URETHANE?, Oil-based, clear gloss- Recommends 3 coats & min 4hours dry time(sanding only if drying for 12+ hours) ==> notes cancer & reproductive harm as well as the need for adequate ventilation, but also the harm go humidity
    • Can I use this product outside?- where should I let it dry?

It has been recommended that I get:

  • sand paper. 200 grit- I would be hand sanding to remove splinters - specif. @ he edges where the wood was cut, but I'm assuming I'd have to do the entire board for the primer to adhere - so I'm wondering if there's a correct way to do this...

I think I need:

  • Goggles
  • Respirator
  • Coveralls 
  • Knee Pads
  • Mixing & Storage Containers
  • 1gal. Heavy Body Acrylic Paint-,at least 6 colors- including neutrals? (white, black, brown)
  • 1 Gal. Isolation Coat
  • 1 Gal. Solvent- for the Varathane?, I don't know the exact details of this product, but when I looked up polyurethane, it req.'d a solvent to be used
  • Mounting Hardware
  • Probably additional Painters Tape & Brushes

All 'clothing items' are for the Varnish & finish products- everything appears to be highly toxic, don't know if there are safer alternatives.

All amts were 'guess-timated' before the addition of the 2nd mural piece and it's different setting.


I am still trying to come up with some sketches to determine the overall composition, but I am wondering:

  • How can I go about choosing colors?- The room is full of very 'non-modern?' colors, very little blues, purples, or even oranges and the colors are very muddy and dark.  I would like to choose a period-appropriate color scheme but still add some brightness to the colors I choose and some naturalistic purples and blues that go with the theme of the piece.  I want to make sure I have a large variety of colors, but not purchase unnecessary colors I could just take the time to measure out and mix.
    • Example- If I have a largely white background, fo I need to purchase white paint, or can I just use the Primer? Do I tint the Primer to make other neutrals or do i need to use paint
  • How can I go about estimating and pre-mixing any batches of specific colors to work with?
  • Is it possible to follow and early-1900s 'recipe' for specific colors and get a somewhat accurate result using paints purchased today?

I'm thinking the wood panels would be used for the outdoor piece that would be on the side of a house and would not move.

Some or all of these panels may also need to be shipped... I'm thinking some of the smaller panels could be used to flank the large doors.  The large panels may have to be shipped with some kind of mounting instructions.

I currently trying to read through various MITRA posts, but these are the more pointed inquiries I can think of for myself...

Thank You,

Martha Rose

Sennilier Gloss Varnish Problem

Question asked 2019-06-25 17:30:16 ... Most recent comment 2019-06-26 12:01:33

​After applying the Sennelier gloss varnish on well-cured, heavy impasto oil paintings, the varnish clouds and flakes off with the slightest of abrasion. It appears flawed. Why is it not bonding better to the paint? What causes this and how can I prevent it from happening? Is this a defective varnish that can be removed? How would I remove it?

Candle Wax Protectant

Question asked 2019-06-22 15:39:13 ... Most recent comment 2019-06-24 08:40:03
Technical Art History Other Studio Tools and Tips Varnishes

​Hi All,

I use candle wax for make art and have been using resin as a sealant. However, it is super shiny and thick. Any suggestions on what I could use to prevent damage and something that is Uber heat heat resistant? Thanks so much and be well! 

Casein and casein/oil tempera techniques around 1900

Question asked 2019-06-23 06:28:50 ... Most recent comment 2019-06-23 23:01:14


I am currently examinating a wall painting form 1901, that was very probably painted using  casein as a binder. Apparently this medium became popular for the use to paint on the wall with artists who usually painted on canvas. Why did it become popular again and what does its popularity has to do with the industrial revolution? Are there manuals and recipes from arts schools from the end of the 19th century known, that are describing this technique for monumental wall painting in Europe and the US?

Thank you very much, your help is appreciated!

Cold Wax Medium

Question asked 2019-06-22 09:09:03 ... Most recent comment 2019-06-23 22:28:55

How long does it take for an application of cold wax medium atop a finished painting to fully cure, so that a second layer of medium can be appplied on top without affecting the first?  Or does the underlying medium stay indefinitely somewhat soluble when a new layer of medium (with some percentage of solvent in it's formulation) is added on top?  Are cold wax mediums that are soluble in mineral spirits (such as Renaissance wax) stronger than those soluble in OMS (Gamblin's cold wax medium); i.e. is the fact that whatever resin in the medium is soluble in a stronger solvent mean it contains a stronger resin?  Thanks, Koo Schadler

Percentage of resin in grinding medium

Question asked 2019-06-20 15:23:33 ... Most recent comment 2019-06-20 15:19:00
Drying Oils

​Dear Mitra,

Although I know that it can be confirmed or denied that the old masters used resins in their mediums I wish to use a bit in mine. 

Whats a healthy amount of Dammar Varnish to put into ones medium? 


Question asked 2019-06-17 12:26:52 ... Most recent comment 2019-06-18 18:19:41
Grounds / Priming Pigments

​The main ingredient in Chloreseptic (an oral analgesic) is phenol, which can act as a preservative or biocide, from what I understand.  I don't know what else the product contains. What do you think about using Chloreseptic in either pigment pastes or gesso to inhibit mold growth?


Koo Schadler

Are certian oils more fat than others ?

Question asked 2019-06-17 16:23:08 ... Most recent comment 2019-06-18 18:02:55
Drying Oils

​Dear Mitra,

It seems that everyone describes fat over lean as simply placing more oily layers over less oily layers.  But are certain oils in and of themselves more fatty than other ones if equal amounts are set out? For a example if I set out an equal amount of a polymerized linseed oil and refined linseed oil is one fattier than the other?  Since one was polymerized does this change its fat/lean state? 

Thank you,

Hector Hernandez

Dyed Canvas Question

Question asked 2019-06-18 14:21:00 ... Most recent comment 2019-06-18 17:20:07


I recently dyed canvas using acrylic paint. This is a process that I use fairly often. The canvas came out of the dye bath having a funny odor, I am wondering if you know of a solution to get rid of the smell, without messing up the canvas? Vinegar?

Making inkjest prints "archival quality"??

Question asked 2019-06-17 10:08:40 ... Most recent comment 2019-06-18 06:03:58
Art Conservation Topics Dyes Environment Ink Photo-Documentation / Digital Printing Pigments Varnishes

​I have studied the materials from Golden Paint regarding using thier MSA varnishes over inkjet prints for UV protection  and it appears that they provide significant protection against fading for dye and pigment based injet prints.

Can injet prints treated with these UV protective varnishes be sold as "archival quality prints"?  

Dammar resin in a painting medium

Question asked 2019-06-13 08:45:15 ... Most recent comment 2019-06-13 22:54:16
Paint Mediums

​ Hi! Is there a minimum amount of Dammar resin that can be safe as an ingredient in oil painting mediums?   It is well-known that large amounts are not acceptable. From my own experience I can say that nothing compares with mastic/dammar painting mediums when I produce/create the painting: blending, flowing, drying rate, tixothropy, etc... But in terms of conservation and durability the story is totally different.  For his recipe (the famous 1:1:5), Ralph Mayer calls for a 5-pound cut Dammar Varnish.  Do you think that 1 part Dammar Varnish in this recipe is excessive, moderate, acceptable? Can be reduce the amount of dammar varnish in this recipe to get an acceptable painting medium, in order to prevent yellowing, varnishing problems, cracking, etc...? Or the answer is simple: NEVER use! Thank you !

Clove Oil for slowing drying rate of oil paints

Question asked 2017-04-25 14:20:23 ... Most recent comment 2019-06-11 02:53:53
Paint Additives Oil Paint Paint Mediums Scientific Analysis Art Conservation Topics

I have a query regarding the section in the MITRA documentation on Solvents about Clove Oil for Oil painting:

"Essential Oil of Cloves or Clove Oil has been used as a preservative in emulsions and as an additive to mediums to substantially slow down their drying rate. There are far better preservatives available today. The use of clove oil as a drying retarder is greatly discouraged as its addition tends to substantially weaken the dried paint film.

Other Essential Oils and Extracts are also periodically used in art making. Oil of rosemary sometimes served as a substitute for clove oil and as a component in the creation of complex oil-hard resin mediums. Like clove oil, artists should forgo the use of these materials as their dangers far outweigh and perceived benefits."

I and many other painters I know use Clove Oil to extend the drying time and I have never read anything negative about using it before.

Please can you tell me what evidence led to the conclusion that clove oil weakened dried paint film.

What were the numbers for the control, clove and rosemary in the studies that were done?

Adhering fabric to plywood

Question asked 2019-06-06 09:57:17 ... Most recent comment 2019-06-06 14:39:31
Rigid Supports

​I've recently started adhering pre-primed canvas to cradled plywood rather than painting directly on the plywood. I seal the wood with shellac on all sides and then adhere the fabric with PVA glue. However, I have some leftover plywood panels from beforehand that I had prepared diffferently or started to use. All of the panels were sized with GAC100 and then either A) primed with oil primer but not used or B) primed with acrylci primer and then underpainted in oils. My question is whether in either of these cases it would be possible to glue fabric over the exiting structure.  I suspect the scenario A (the top layer is oil primer) would have enough tooth to provide emchancial adhesion but I'm less confident of the B scenario (the top layer is oil paint over gesso).  

Mixing Water Media

Question asked 2019-06-02 12:04:16 ... Most recent comment 2019-06-03 19:27:51
Acrylic Casein Egg Tempera Gouache Watercolor

To what degree can watercolor, gouache, casein, glue tempera, egg tempera and acrylic - all water media - be intermixed, or at least used to tint one another?

Koo Schadler

Acrylic, Oil painting Air Quality Comparisons

Question asked 2019-05-31 09:00:12 ... Most recent comment 2019-06-03 10:29:27
Oil Paint Studio Tools and Tips

​I wonder if there have been any studies comparing the air quality, when using acrylic paints versus oil paints without solvents. My oil painting class is treatened because of lack of ventilation.

Varnishing with a regalrez based varnish too soon.

Question asked 2019-05-19 21:24:29 ... Most recent comment 2019-05-31 18:12:24
Oil Paint Varnishes

​The general advice is to wait 6 - 12 months before varnishing an oil painting.
Specifically regarding regalrez based varnishes, Gamblin suggests that a painting can be varnished with Gamvar as soon as it is touch dry, which contradicts advice from George O'Hanlon and Virgil Elliot.

What I would like to know is, what are the consequences of varnishing too early with a regalrez based varnish?

Varnish suitable for both oil and acrylic

Question asked 2019-05-29 18:42:31 ... Most recent comment 2019-05-30 23:27:53
Acrylic Varnishes Oil Paint

​I often see artist wanting to leave raw canvas showing in their paiintings.
Recommendations for this are to use a GAC product from Golden, or a clear acrylic polymer as a barrier.

So if someone were to have a surface of both acrylic and oil, what varnish/s would you recommend that could be removed from both without damaging the paint?

George O'Hanlon recommended an isolating coat before the final varnish, but I imagine the isolating coat would eventually need to be removed as well at some point.

Ron Francis

Large amounts of oil for oil paints

Question asked 2019-05-28 02:23:33 ... Most recent comment 2019-05-29 11:15:19
Art Conservation Topics Drying Oils Oil Paint Paint Mediums Scientific Analysis Rigid Supports

Hello all,

I've done a couple of experimental paintings lately with a large amount of walnut oil added to tubed oil paints and mixed until the paint has the consistency of cream/thin yoghurt.

I have seen no wrinkling with the walnut oil (I expect there would be wrinkling with stand oil or plain linseed oil)

I am sure that the paint films will be less archival than using a minimum of oil, but if painted on a rigid (Dibond) surface would you expect that they would still last for decades, or fail within a few years?

One of the reasons I'm not sure is that I'm read that extenders and filler pigments like PW5 can make a paint film weaker, yet they are used a lot in student grade paints.


Polishing an egg tempera painting

Question asked 2019-05-08 17:19:48 ... Most recent comment 2019-05-24 23:03:02
Egg Tempera

Hello! and thank you for this wonderful forum!

Many ET painters find themselves painting smaller and smaller works but I am the opposite. My paintings tend to get larger and larger. I just completed an 8'x4' ET and it "only" took 2 years! Ordinarily I would polish my painting with a soft cloth: silk, flannel or T-shirt material has been recommended and I have not found much difference between them. Due to the large size, and some physical limitations, I am experimenting with power tools. I've tried a "polishing bonnet" attached to my corded electric drill but am interested in purchasing a dedicated buffer. A Dual Action Random Orbital Polisher  (DA) seems to be the safest option, in terms of not harming the surface,  but I don't want to invest in it unless I feel it will be more effective or safer than my drill buffer or hand polishing. The "bonnets" I am using now are what came with the conversion kit- one is lamb's wool and the other an unknown synthetic. If I get the DA there seem to be endless options in polishing pads. Of course they are meant for automotive polishing. I love traditional methods/ materials but am not one to scoff at high tech improvements. Perhaps the old saw about ET developing a gentle egg shell gloss will be proven a myth once more effective polishers are employed and a higher gloss will be achieved (not that I necessariy want that.) Obviously if I see any paint on my bonnet I'll know the machine is too aggressive or the paint surface inadequately polymerized. So far I have tried it on the edges of my monster ET panel and no paint has come up, nor have I achieved any more shine than with elbow grease. Hoping you might have some experience with this. Perhaps conservators use electric buffers with a variety of pads? If not my path would be clear: buy the DA and try different pads on castaway paintings or trial paintings and see what the effect is. Thanks much for your great work!

Lora Arbrador

CPVC in Tempera

Question asked 2019-05-14 10:42:38 ... Most recent comment 2019-05-22 08:49:15
Egg Tempera

My experience has been that a well-tempered egg tempera paint (good handling properties, consistent shine, etc.) has a CPVC of about equal parts yolk to pigment.  I've always puzzled at the greater variability, at times, of pigment to binder ratios in oil versus in tempera, which has much less variability in that regard - almost all colors temper well at equal parts yolk and pigment, with just a few minor variations (some lean, thirsty earth colors, like burnt umber and sienna, need a wee bit more yolk; fatter viridian needs a tiny bit less).  One would think that whatever variabilities in pigment to binder ratio exist in oil would transfer to tempera - but they seemingly don't. 

And while I've heard the terms "fat" and "lean" used to describe a pigment's need for more or less binder, what acutally determines if a color is fat or lean (and, back to my original question, why does that need seem to vary from one medium to another)?


Koo Schadler

Egg Tempera as Metalpoint Ground

Question asked 2019-05-14 10:10:46 ... Most recent comment 2019-05-20 10:55:33
Grounds / Priming Egg Tempera Drawing Materials

​Hello MITRA,

I've been playing with egg tempera as a ground for metalpoint.  If layered thinnly and allowed to cure egg tempera is, like casein, a good ground (due to its PVC); yet I rarely see tempera mentioned as a metalpoint ground.  Any thoughts?

Also, is egg tempera as vulnerble to hydrolysis as oil paints?  


Koo Schadler

oil painting in the aeroplane

Question asked 2019-05-15 14:04:02 ... Most recent comment 2019-05-17 10:47:12
Handling and Transportation

​Dear Mitra,

i was comissioned an oil painting that I will have to take with me from Europe to South America. This means at least two changes of airplane and a 13 hr long flight in between. The painting will be 90x100 cm. As it will be newly made and flexible when we fly, i assume there will be no problems with rolling it, as far as done correctly. I wonder if there is a save way of bringing a painting in an aeroplane, a way of packing it where it can be sent safely it with the checked baggage. Advice and tips will be much apreciated. 

Thank you!


Using a marble stone as a palette

Question asked 2019-05-11 21:28:28 ... Most recent comment 2019-05-13 10:47:19
Oil Paint

Before using a marble stone as a studio palette ( 16 x 22 inches), I wanted to check with you for any special preparatory treatments that may be required for the marble surface prior to oil painting.

I believe the marble top is older (resale store bargain purchase)  and possibly one made from a combination of marble powder and stones.

Your suggestions and ideas are always helpful.


WMO Oil paints and traditional oil paints

Question asked 2019-05-08 15:13:08 ... Most recent comment 2019-05-10 20:24:06
Oil Paint Solvents and Thinners

Hi all,

If I do a layer of a painting with WMO oil paints mixed with water as a solvent, and then I paint over the top with traditional oil paints (because of more pigment choices, etc..) will this cause an issue? Would the water remain trapped in the WMO paint layer, or will it evaporate through the traditional oil paint layer?

I have read that it takes a lot longer for all the water to actually evaporate out when using acrylics, so is the same the case for oil paints?

Are you aware of any issues with paintings done in a mix of WMO and normal oils in this manner?

Thank you,

Traditional drying oil - hard resin varnishes

Question asked 2019-05-05 15:19:41 ... Most recent comment 2019-05-09 19:13:48
Drying Oils Scientific Analysis Solvents and Thinners Varnishes Art Conservation Topics

Dear experts! I have several questions about traditional sandarac and copal drying oil-resin varnishes.

1. In various articles I encounter mentions of good preservation of such varnishes after hundreds of years, for example, in case of paintings by Carlo Crivelli or Orazio Gentileschi. Are those cases just coincidental exceptions or drying oil-hard resin varnishes age better than their cousins made with oil and colophony, larch balsam or mastic?

2. Is it absolutely necessary to heat sandarac or copal resins in oil to make a good varnish? Or maybe I could use an intermediate solvent to avoid extensive thermal treatment?

3. Could I use modern zirconium-calcium octoate drier additions instead of traditional lead linoleate? How much worse are such driers than lead-based ones in the long term?

4. How important is to use fresh Cypress or Juniper sap instead of dried and oxidised resin which is always sold in art supplies stores? In Da Vinci’s recipe use of fresh sap in spring is recommended.

5. Could I enhance ageing performance of such varnishes by adding Tinuvin 292 and 1130? Or maybe using other modern additives?

6. I’ve heard that new methods of old varnish removal gain popularity, such as laser ablation. Could I rely on such technologies for future conservation efforts of my paintings or I should care about varnish solubility and use Regalrez 1094 with Tinuvin 292 because they remain soluble despite their not so good appearance, scratch resistance and necessity to wait one year before varnishing?

Thank you.


Question asked 2019-05-07 12:28:08 ... Most recent comment 2019-05-09 12:38:12
Oil Paint


I'm having problems with underbound imprimatura since I upgraded to artist quality oils. I guess part of the "problem" is the higher pigmentation of my new oils. I can't seem to achieve a bound yet semi transparent layer of paint. I'm diluting burnt umber with mineral spirits. I've recently had the same problem with an opaque venetian red ground I layed out on another canvas. In that case I oiled out the entire canvas. I tried to do the same with the raw umber imprimatura, but in rubbing the oil I ended with a brown surface and my underlaying drawing completly lost.

Am I using to much solvent? How can I achieve a semi transparent imprimatura that is bound enough?

Thank you for your valuable advice!


Varnish or fixative for Prismacolor, and graphite

Question asked 2019-05-07 15:00:49 ... Most recent comment 2019-05-08 07:38:45
Pencil Varnishes Other Art Conservation Topics

I am doing large scale drawings/rubbings using prismacolor sticks in some and graphite in others. These are too large to frame -- some will never be covered (and will be rolled to ship and stored with glassine over top), others will be covered with a sheet of Plexi (offset from the surface)

I will break this into a two part question:

1) Prismacolor: I am concerned about lightfastness and wondered if there is a suitable spray or brushable varnish that can provide UV protection for the Prismacolor. I am only using the Level 1 and 2 lightfast colors. (If there is a better quality color pencil in stick form--please let me know. I have not been able to find much information)

2) Graphite: final fixative that will protect if the drawing is rolled or brushed against since there may not be any plexiglass?

Thanks very much.

rabbit skin glue

Question asked 2019-05-03 15:17:17 ... Most recent comment 2019-05-07 12:34:10
Animal Glue

​Hi, I just read somewhere that rabbit skin glue only smells when it has gone bad... Is this true? I had never heard it before, assumed the smell was normal. Now I worry that the glue I just sized some canvases with is bad.

Effects of ageing and conservation efforts on Renaissance egg tempera paintings

Question asked 2019-05-01 04:45:56 ... Most recent comment 2019-05-03 14:02:17
Art Conservation Topics Egg Tempera Scientific Analysis Oil Paint

Dear experts! I am an amateur painter interested in other’s works. When I look at portraits by Botticelli, I do not understand what do I see. My guess is that nowadays his paintings are very different from what was intended. So, I have several questions. For example, let’s consider his Portrait of a Young Man (Washington). 

1. What do I see at the edges of paint flakes divided by craquelure? I think that when the ground layer cracked, separate flakes slightly curved and their edges raised. Next, paint near edges of flakes was abraded during handling and cleaning of the painting, upper layers of paint were stripped. So at the edges near minuscule cracks I see lower paint layers. Is this correct?

2. How transitions between light and dark parts of the face were applied, particularly at the nose and cheek? I see darker spots of paint without clearly defined edges. They appear to be spatially oriented as if they are parts of longer brush strokes. What causes this interrupted appearance? Are they a result of paint abrasion? Or his panel was grounded with some texture and we see an effect similar to watercolour granulation on rough paper?

3. Opening the image in GIMP and using a CIELch colour picker reveals complex variations of hues, particularly at skin areas. How such variability was achieved? In my understanding of egg tempera technique, a painter mixes pigments in raw state, grinds them on a stone with binder and puts resulting paints in dishes. Without mixing on a palette since tempera dries fast. I have several guesses, but what is correct? Perhaps, many pigment mixtures were composed in raw state? Or he composed just a few pigment mixtures and applied them in several very thin layers of varying density? Or he used tempera grassa which dries slower and mixed it on a palette like oil paints? Or the painting was heavily overpainted during many conservation efforts and we see a result of using slightly different pigment mixtures by restorers? This is certainly the case near some major cracks and scratches, but to what extent other areas are overpainted? 

4. Is there a darker layer of paint under light areas of the skin? Or lighter parts were painted straight on a white ground with some sketch made with dark coloured lines? I guess I see darker underlayer in a lower left corner of his neck near the fur collar.

5. What happened with some hairs of the left eyebrow (model’s right eyebrow)? I see crisp lines of dark coloured paint but a couple of lines are very dim. Were they abraded? Or they are parts of preliminary drawing covered by subsequent paint layers?

6. The overall skin color is very yellow, about 1/3 more yellow than a real skin color of a Caucasian man could potentially be - I am judging by CIELab colour coordinates and limits given in an article by A. Chardon «Skin colour typology and suntanning pathways». I wonder is this a result of binder or varnish yellowing? Or an artistic choice to make it look more saturated?

7. The color of his fancy hat is puzzling. Too orange for an ordinary cinnabar. I guess its color is an effect of particle size - somewhere I’ve heard that very finely ground cinnabar turns almost to carrot-orange. Or is it a result of fine glaze applied atop of cinnabar? Or another pigment was used too, like realgar or orpiment? 

I would be grateful if you’ll share your opinions and point me towards research papers to read. Thank you.


Question asked 2019-04-26 20:41:17 ... Most recent comment 2019-05-02 10:21:09
Egg Tempera Health and Safety

Hello everyone. I have a question concerning  health issues as I am going to begin doing egg tempera.  Seeing that we handle pigments I think it is preferable to wear a protection mask so as not to breathe or inhale the toxicity of the pigment. Could you give me some advice on that I can anticipate? Thank you.

Minor warping of Baltic Birch plywood with traditional RSG gesso.

Question asked 2019-05-01 09:37:26 ... Most recent comment 2019-05-01 12:33:35
Animal Glue Egg Tempera Rigid Supports Grounds / Priming

Another panel question!

 I recently purchased a 5'x5' sheet of ¾" Baltic birch plywood and cut into 30"x30" pieces for use as panels.

For two of these pieces:

I applied a coat of RSG size, muslin adhered with RSG, and 8 layers of traditional gesso on BOTH SIDES of the panel. Save my application of cloth to both sides of the panel, my method generally followed instructions for gessoing detailed in Daniel V Thompson and Koo Schadler books. About 3 days of drying and the panels have warped a small amount in one direction. If I set a rigid rule from edge to edge of the panel, I can see about 1.5-2mm space between the center of the panel and the rule. Hanging the panel on the wall, the warp is barely noticeable, but I wonder, is this evidence of even greater instability of my panels in the near future? Or, if I'm willing to accept the current warp, could I paint them (with egg tempera), shellac the back, with any confidence?

I've had extremely bad luck workign on plywood and also custom made panels in terms of warping at the gesso stage at this scale of 30"+

Still learning a lot from this forum, thank you,


Adhering Paper to Aluminum Sheet

Question asked 2019-04-23 13:27:58 ... Most recent comment 2019-04-27 19:46:22
Rigid Supports

​I would like to adhere a 30 x 44" sheet of  paper to a 1/4" sheet of aluminum 31" x 45" so that I can achieve a 1/2" aluminum border around the paper that will have  a machine-routed, 'mirror-finished' polished edge, similar to a glass beveled edge. I was told by Talas Conservation Materials that Bevo 371 drymount film would be the best canidate for a hot press, given its low temperature adherance rating at 150 degrees farenheit, and therefore not warping the sheet metal in the heat press. I am not certain how to prepare the main body of aluminum underneath the paper ...questioning if the metal will oxidize the paper sometime down the road or if it will remain relatively stable in typical gallery/museum envirnoments? I have found nothing negative attibutable to oxidation of aluminum as a rigid mounting surface that might affect the paper. So I am actually seeking best advice on mounting the paper to raw aluminum sheet given the use of the Bevo 371 film by itself. The aluminum is typically what I would purchase from an industrial supplier of  1/4" sheet aluminum. Can you help?


Using only oil as medium

Question asked 2018-01-31 18:43:27 ... Most recent comment 2019-04-25 08:30:27
Oil Paint

Is the practice of using only oil - without any solvent - sound? Presuming I don't use an excessive amount of oil (meaning, one that would create a layer of its own, separate from the paint), would the produced paintings be technically sound, from a conservation standpoint?

Assuming that this is the case, is there any sound way to speed up the drying time without toxic chemicals (siccatives etc.)?

alkyd oil ground

Question asked 2019-04-23 04:32:22 ... Most recent comment 2019-04-24 17:05:26
Alkyd Animal Glue Flexible Supports Grounds / Priming Oil Paint

​Dear MITRA team,

I've read through a lot of the existing threads but I do still have some question on the sizing/priming of flexible supports. 

Regarding rabbit skin glue, I understand that most artists have decided against it's use by now. But I would still like to know if conservationists unanimously advice against the use of RSG on flexible supports (like they have done with, for instance, the use of Zinc Oxide) or if it is more a matter of preference and which risks one might be willing to take with the material. I'm also not so clear on how do disadvantages of using RSG compare those of using PVA glue or acrylic size. I do understand the problems with cracking, but I'm still interested in using RSG for stiffness. I have to say, another reasons for me considering it is somewhat romantic. I like the idea of using a material that has been used and regarded as the best option for centuries. I'm aware of the faultiness of this logic though. So, please help! 

My second question would be is it would be ok to use an alkyd based ground (I'm thinking titanium white, marble dust or similar, alkyd binder and maybe some oil) on top of the RSG or PVA, and under oil painting. I would do this mainly for time convenience (drying time). I wonder if succesive coats of oil would adhere well to the alkyd ground, that results quite glossy. 

Finally, I would like to know how many coats of glue and how many of ground you would recomend for best results on flexible support. 

Thank you so much for your great work! 


Tradition Gesso to Fiberglass

Question asked 2019-04-21 15:07:33 ... Most recent comment 2019-04-22 23:13:52
Animal Glue Rigid Supports Sizes and Adhesives Art Conservation Topics Egg Tempera

​One more panel and traditional gesso question:
I was recently given a sample of honeycomb aluminum faced with fiberglass. I applied 4 coats of traditional gesso and after a week of dry time did a cross-hatch adhesion test. The adhesion seemed good. Anyone have experience with these materials? I don't know how fiberglass registers wil best practices but it seems like a potential solution for egg tempera paintings at a larger scale. Thanks in advance! - eli

Adhering Muslin or Linen to ACM for use with Traditional Gesso and Egg Tempera

Question asked 2019-04-21 12:03:40 ... Most recent comment 2019-04-22 17:46:37
Animal Glue Acrylic Art Conservation Topics Egg Tempera Grounds / Priming Rigid Supports Sizes and Adhesives

I'm looking for more panel advice, in this case to adhere Muslin or Linen to Aluminum Coposite Material. In my case Honeycomb aluminum for use with traditional gesso and egg tempera. I've heard BEVA works well but I hope to use at a scale of 30"x30" to 50"x50" and I don't have a heat press. Any thoughts? Or PVA could work: I've used Gamblin PVA to size linen in the past but that seems too watery for adhereing cloth to the ACM. Is there a good PVA Gel or glue? Finally, I've used Acrylic gel medium to glue paper to wood panels, could Acrylic gel adhere cloth to ACM? Thank you! - Eli

A Composite Surface Made from Joined Pieces of Linen

Question asked 2019-04-19 16:42:13 ... Most recent comment 2019-04-21 00:47:28
Flexible Supports


I am researching ways to sew together individual pieces of linen (like a patchwork quilt) to be stretched over a rectangular stretcher. Eventually, I would like to do this at a very large scale, but for the moment I am just making studies. I am currently working with Claessens oil primed linen #13, which I have on hand. I wrote to Claessens to inquire about the weight of the thread they use in weaving this particular product, and they said it was nm 40. I have ordered a linen thread that is two-ply and advertised as 40 (though I wonder if there might be a difference because I am purchasing it in the US and we don't use metric?). My thinking is that matching the thread weight/strength as best I can will help keep the seams from slowly destroying the linen squares under tension over time. A friend suggested that using a sewing machine will help keep the seams even, and thus will spread the tension more evenly across the matrix than a hand-stitched textile surface would.  

I wonder if anyone on this forum has suggestions for me (aside from the obvious "don't do this," lol!) Do you think linen is a good choice? The person I corresponded with from Claessens suggested that a synthetic fiber might be best. Linen has historical resonance that I appreciate, and it is strong, but I'd be willing to work with polyester if that seems more adapted to my purpose. I work in oil paint and use a simple gamsol/linseed oil medium. Do you think the Claessens pre-primed oil primed linen is a reasonable choice here, or do any of you think I would be better off with a different sort of priming under my paint layer? (Ideally I would like to paint on it and then cut it up and sew it together, not sew it and prime the resulting matrix as one surface). It seemed to me that a commercially made product would be likely to be more consistent than something I primed myself. If there is anyone out there who knows about large-scale textile display (quilts and rugs and the like) are there technologies I should consider for supporting this textile painting-quilt hybrid from the back? Any references you could give me would be much appreciated! 

Thank you!

Krista Schoening


Using newsprint in mixed media work.

Question asked 2019-04-17 02:52:27 ... Most recent comment 2019-04-21 00:38:57

I make mixed media work with a lot of paper elements, mostly drawing papers which I paint watercolor. However, I also use newsprint which I glue onto areas of acrylic paint and rub some of it away, and then paint that in watercolor. It bothers me knowing that newsprint yellows over time, and although changes to my work and the watercolor paint I later paint this paper has not had any color shift, ​I would like to chose a better alternative. I need a paper that is thin, short fibered, that can absorbed water-based paint. Nothing caught my attention at the art supply store, except for layout bond.

Generally I seal these areas using a product called Polycrylic.

Using heat to remove dents in stretched canvases

Question asked 2019-04-19 18:28:43 ... Most recent comment 2019-04-19 19:38:09
Drying Oils Flexible Supports Oil Paint

​Regarding an oil painting on stretched canvas, I have heard a suggestion that one can use an iron on a low heat on the reverse side to flatten dents or folds.
Elsewhere, it was said that heat will damage oil paint.
I'm pretty sure that I have read that applying heat is an acceptible technique from a qualified source, but can't remember where.

Csn you please give you views on this.
(Assume that the paint layer is thin, flat and smooth.)

Canvas Stretching and Desirable Tension of Canvas

Question asked 2019-04-19 15:48:06 ... Most recent comment 2019-04-19 19:32:31
Oil Paint

How much tension should be placed on the canvas when stretched over wood bars and is it necessary to secure the stretcher bars together prior to stretching the canvas?


My reason for asking is prompted by my method of stretching the canvas. I use a Fredrix style 22 cotton canvas that is unprimed at 7 oz. and primed at 11.5 oz. , plus an additional four coats of quality Gesso is applied to the stretched canvas.

Tightness of the canvas allows for a "hollow" sound when thumbing the face side and there is some slight tension pull shown at most staples.

Will the canvas tension impact the oils after several years?

Is it advisable to secure the corners of the stretching bars or let the canvas maintain a good corner square? I have personally seen both methods used and am concerned if there is an advantage over one method.

Patrick McGuire

Regarding Best Ratio for using Zinc White/Titanium White Combination

Question asked 2019-04-16 15:06:51 ... Most recent comment 2019-04-19 15:48:58
Oil Paint

Several authors have recommended using a combination of Zinc White and Titanium White for use in landscape paintings especially for imagery of clouds; ratios of varying amounts including one part Titanium to 3 parts Zinc White. Book sources ranged from 1974 up to the present and written by established painters.

I have personally used one product that offers a premade mixture of the two whites. However, I would greatly like to learn of using various ratios of Zinc White combined with Titanium White to achieve sky and tinting effects in landscape paintings along with the potential risk of Zinc White having a possible long term change.

Your ideas and suggestions are appreciated.


Patrick McGuire

Tucson, AZ

Adhering Copper to Panel for Oil Paint

Question asked 2019-04-17 11:10:17 ... Most recent comment 2019-04-17 11:55:14
Grounds / Priming Sizes and Adhesives Rigid Supports Oil Paint

​I would like to adhere 3 ml - 5ml copper sheets to a panel surface to paint. What is the best practice for adhering copper this thick to panel? Is a different thickness recommended? Also, what is the best practice for preparing the copper to receive oil paint?  

Layering different water-based media

Question asked 2019-04-16 19:06:16 ... Most recent comment 2019-04-17 11:46:13
Acrylic Gouache Ink Watercolor

From a conservation point of view, would it be a problem to layer acrylics, gouache, watercolors, inks, etc. over each other? For example, would a layer sandwich of:

  1. Watercolor
  2. Acrylic
  3. Gouache
  4. Acrylic

(or some other combination) be a problem? I'd imagine that, once dry, the acrylic layers would keep everything below set.

ACM - RSG gesso - will it stick?

Question asked 2019-04-16 22:45:10 ... Most recent comment 2019-04-17 10:14:17
Animal Glue Egg Tempera Grounds / Priming Sizes and Adhesives Rigid Supports

Does traditional RSG gesso adhere well to anything besides wood? I'm struggling to find a good solution for egg tempera painting at somewhat larger than traditional scales, about 30" square. I've had very mixed results in terms of warping panels when applying traditional gesso to high grade plywood of various thicknesses (both cradled and not) at a scale of about 30" square. I adhere a layer of cotton muslin to the face of plywood panels, also with RSG, to avoid checking, and also gesso both sides of the panels. My new fantasy is that if there really are adhesion issues with RSG gesso to materials like aluminum, fiberglass, etc what if linen or other fabric was glued to one of these materials?  The fabric could enjoy an industrial bond or a BEVA bond to the ACM or whatever kind of stable support and then the traditional gesso could enjoy a bond to the openness of the fabric… thoughts? (I've found one fine art manufacturer who suggests the surface of their ACM panels will take hide glue just fine, even without the interlayer of fabric, but they don't sell panels at a scale large enough for my purposes.) Thank you for thinking about this with me!​

Sealing Wood Panels with Shellac for egg tempera painting (Will RSG adhere to shellac?)

Question asked 2019-03-15 13:06:25 ... Most recent comment 2019-04-17 02:58:48
Egg Tempera Rigid Supports Grounds / Priming

I have two questions regarding my particular case of preparing cradled plywood panels for egg tempera painting

1. Will traditional RSG and/or RSG gesso adhere to a panel that has been sprayed or brushed with Shellac?

2. Is it reasonable to seal a plywood panel with Shellac to keep moisture out and then use that panel with traditional RSG and/or gesso? From my research and experience it is common to simply size wooden panels with RSG first, and then continue to apply RSG gesso. However given the hygroscopic nature of both the wood and RSG, wouldn't sealing with Shellac first at least help reduce movement and other problems caused by moisture? The panel manufacturers I have been talking to in New York certainly encourage sealing panels with Shellac but the majority of their customers are working with acrylic and oils, not traditional gesso and egg tempera. What do you think?

Thank you, I love this forum btw!


Eli Bornowsky

Acrylic Isolation Coat

Question asked 2019-01-29 18:43:38 ... Most recent comment 2019-04-17 02:43:56

The only recommendation I have ever found for what to use as an isolation coat is a mixture of water and Golden soft gel gloss. Are there other products that make a good isolation coat, with or without mixing with water? I am interested in a brushed, not sprayed, application.

Flashe paint preservation in the jar

Question asked 2019-04-14 09:08:29 ... Most recent comment 2019-04-16 18:53:12

​I have many colors of Lefranc & Bourgeois Flashe vinyl paint, and am not using them quickly. I've noticed that they tend to harden in the jar, though I'm careful to keep the jar threads and lids clean and screwed on tight. I don't want to add water and potentially create mold, and am wondering if anyone knows a good vehicle to thin this paint and keep it usable longer.

Question regarding a Final Oiling Out and Temperature Effects on oil

Question asked 2019-04-16 11:07:04 ... Most recent comment 2019-04-16 14:23:04
Oil Paint

An observation was made on two types of finished oil paintings: stretched canvas and canvas panel on paper hardboard, that reveal some type of impact heat may have on the thin layer of walnut oil rubbed over the final painting before varnishing.

After the first week of drying time, a nice oily shine appeared on the canvas. At the end of the third week under much higher temperatures (85 to 100 degrees F ), the surface now showed a visible dry and flat appearance as if no walnut oil was applied.

Each painting used a quality canvas, received four (4) additional coats of gesso and quality oil paints were used.

Did heat change the appearance of the walnut oil and it remains on the surface, but not in a shinny wet appearance?

Did the heat evaporate the walnut oil product?

Did the higher temperatures allow for the oil to be absorbed into the painting, requiring additional coats of walnut oil prior to the application of varnish?

Your thought would be most appreciated!

Patrick McGuire

Tucson, AZ

Oil Paint over Acrylic Molding Paste

Question asked 2019-04-13 17:03:52 ... Most recent comment 2019-04-15 11:04:41
Oil Paint Paint Mediums


I want to start exploring impasto techniques and more sculptural techniques with oil paint, and I'm trying to learn the best ways to do that without my painting falling apart. I like to paint on wooden panels so I was wondering if I could use a product like Golden's molding paste to build up a texture, and then paint over it? What steps would I need to take to do this properly? My current plan would be to size the panel with GAC 100 x2 layers, then 2 layers of acrylic gesso, then the molding paste on top. Does the type of molding paste I choose matter?

I also bought an impasto medium from W&N to try out, but thick oil paint layers can take a while to dry which is why I wanted to explore other options. I don't want a case where my paint never dries properly.

Intermixing Acrylic Paint

Question asked 2019-04-12 15:27:11 ... Most recent comment 2019-04-13 07:22:00

​What are the risks of intermixing brands of acrylic paint; for example, a jar of Liquitex white tinted with a color from Golden or Dick Blick?


Koo Schadler

Dibond Vs Plywood panel

Question asked 2019-04-10 10:18:39 ... Most recent comment 2019-04-10 11:54:08
Acrylic Art Conservation Topics Rigid Supports


I usually paint small and use either dibond or plywood panels. I am about to start a larger piece (in acrylics): 60x100cm and I wonder which support should be better. Dibond is lighter but isn't it more fragile and ready to bend? Heavy outdoor plywood is obviously very heavy but looks stronger to me. What do you think? Thank you.

Best regards,

Thomas Ehretsmann (France)


Question asked 2019-04-08 15:36:08 ... Most recent comment 2019-04-08 18:24:48

​I am writing about imprimatura and have 2 questions.

Can an imprimatura tone a ground ANDan underdrawing or should it read ground OR underdrawing?

I know that an imprimatura can be a translucent glaze of paint, can it also be a colored size or colored varnish?

Gilding on Paper

Question asked 2019-04-03 15:16:04 ... Most recent comment 2019-04-04 12:54:12

​What is the best practice for gilding on paper? 

Waterbased varnish for oil

Question asked 2019-04-01 15:34:25 ... Most recent comment 2019-04-01 23:01:09
Acrylic Drying Oils Varnishes Oil Paint


I have recently come across a waterbased varnish (Acrylic resin 80%; stabilisers - according to the manufacturer's website) that is recommended as a product for varnishing oil or acrylic paintings. I have never seen a waterbased acrylic dispersion varnish recommended for use on oil paintings before.

I am curious as to your viewpoints on this. Specifically regarding adhesion and ease of removal.

Many thanks.

Spray applying Gamvar matte varnish

Question asked 2019-03-25 22:39:44 ... Most recent comment 2019-03-31 21:14:25
Varnishes Oil Paint

​Hello all,

I have been experimenting with Gamvar matte varnish to even out the alternatly dull and shiny areas in my oil paintings, which have large flields of flat color over a smooth surface. The brushstrokes from the varnish application are showing up when the varnish dries and it's distracting to the work. I understand that matte Gamvar is the trickiest to apply and am experimenting with different techniques. In the meantime, I asked a Gamlin product specialist on the phone about spray-applying the matte Gamvar, which they said required a proper respirator and ventilation, but is a common practice for conservators. Has anyone attempted this and can you offer tips before I give it a try? Would this require an air compressor, or can I use a Preval sprayer? Finally, is there a company or conservator anyone can reccomend in NYC that I might be able to hire to do this for me? I reached out to some prominent NYC art materials and finishing companies but so far am coming up dry. Thank you in advance!


Metalpoint Fixative

Question asked 2019-03-29 11:52:21 ... Most recent comment 2019-03-31 19:41:30
Drawing Materials Varnishes

I want to explore the idea of applying fixative or varnish to a metalpoint drawing.  My reasons are:

1.  I combine metalpoint with fairly developed egg tempera painting on panel (see attached as an example: metalpoint lettering & egg tempera rabbit on Golden black gesso); the work, to me, appears too "removed" from the viewer when framed under glass - so I'm looking for a way to frame without glass that will nevertheless give some protection to the surface; i.e. a light spray coating of B-72, followed by a wax medium.

2. In my metalpoint experiments (described in an earlier MITRA post) some metals and grounds, when exposed to a lot of sulfur, faded or completely vanished.  I understand the lesson: trying too rapidly to speed up tarnishing can be detrimental to a drawing. However, it also points to the potential vulnerability of metalpoint lines; the insecurity of their attachment to a support.  I realize there are many centuries-old metalpoint drawings in good shape, so I don't mean to say it's not a durable medium; only that it also has the potential to not hold up well. Additionally, I've heard two artists comment that drawings on "Plike" paper tend to "fade" or lose their metalmarks, but many metalpoint artists love working on Plike.  Would a fixative be a good idea for those people who opt for the convenience of a pre-made, less-than-ideal metalpoint paper?  

I understand that a fixative (depending on how sealing or heavily applied) may slow or completely stop the tarnishing effect, but what if an artist doesn't mind or actually wants to deter tarnishing?   Would a light coating of fixative still allow for tarnishing?  

In short, if fixatives are suitable for other forms of drawing, are they suitable for metalpoint as well?  

Tho' I'm interested in subjective preferences, I primarily want to hear the objective, technical pros and cons.



Exposed White or Clear Gesso

Question asked 2019-03-29 17:49:06 ... Most recent comment 2019-03-30 17:58:20
Varnishes Oil Paint Grounds / Priming

​​Is there any technical reason why it would NOT be a good idea to leave parts of a white acrylic dispersion (gesso) or clear matte acrylic dispersion (matte medium) ground exposed in the final painting, which would ultimately be varnished? This would be oil painting. I'm also wondering if a varnish, i.e. Galkyd, would look different over the oil paint areas vs the exposed gesso areas. Thank you for any thoughts.

Polyester Canvas

Question asked 2019-03-24 17:53:34 ... Most recent comment 2019-03-25 16:40:35
Flexible Supports Oil Paint Art Conservation Topics

​Apart from possible aesthetic considerations, a polyester canvas would seem a more ideal flexible support than linen or cotton, at least in longevity.  Less reactive to humidity, embrittlement and bacterial attack, it would appear almost perfect.  

Except, what about heat?  What damage would occur should some future person try to iron it down to another support?   Would the polyester reach a temperature likely to cause damage in a way that say, linen wouldn't be in a similar procedure?  When using a polyester canvas should we make sure that we find some form of pre heat shrunk material?  Is this even available, or is it something already standard in polyester artist canvases?

Checking wood

Question asked 2019-03-25 11:33:22 ... Most recent comment 2019-03-25 13:31:03

​Hello! I've an acryllic painting on a piece of  1 inch standard plywood (smooth on top) that is beginning to check. The wood was sanded, then a primer was put on top, and then the acryllic paint was applied. The painting was begun in December 2018. Is there a way to prevent or stop the checking with the painting already done?

Tacks or staples?

Question asked 2019-03-24 17:21:16 ... Most recent comment 2019-03-24 19:53:39
Flexible Supports

​Are either considered to be more ideal in stretching canvas?

I've used both and find the tacks to be a little more adjustable.  That is to say I can more easily remove and reposition them.  Though one wonders about the impact shock from hitting them in.  On the other hand the staples also seem to go in with quite a "bang".   Not much of a concern with a yet to be primed surface, but what about restretching old paintings?  Could old paint be loosened from the canvas?

Making paint "long"

Question asked 2019-03-24 14:35:27 ... Most recent comment 2019-03-24 19:07:43
Oil Paint Paint Making Mural Painting

​Hello Mitra,

I am going to make some large format paintings for certain commissions.  Since the paintings are extremely large i find tube paints inadequate because they are too "short".  Although i know tube paints are grounded to perfection they dont leave "long " and flowing brushstrokes that will allow me to work faster and in the style i want.  

Since these paintings are going to be alla prima, I want a fast flowing paint that its vehicle is adequate for what i want and also not going to self destruct because of poor formula for the vehicle.  

Is there a wax and linseed oil formula that can be recommeded?  I say wax because i heard that  wax would give me a "long" paint.  

If wax isnt adequated what does Mitra recommend? 

Thank you,



Question asked 2019-03-21 13:40:15 ... Most recent comment 2019-03-21 18:35:14

I am working on some definitions; the definiton I am working on right now is glair.

My first step is reference books and then I go to primary sources whenever possible. My resources, older reference books, state that glair is used for bookbinding, gilding, and painting watercolors on parchment. I talked with one bookbinder and he gave me his recipe for preparing glair and said it was used most for tooling and gilding simultaneously. He said that he used a “bone folder” (non-metal) for folding vinegar and skim milk into frothy egg whites that had set. However when I tried to verify with other book binders no one had heard of it. Is my first source reliable? Is the term bone folder in common use?

I also contacted artists working on parchment. Only one had heard of glair and she didn’t know if it was still in use. She later said that one of her colleagues uses glair with dry pigments when painting and gilding on parchment but she didn’t know if he made his own glair or bought the commercial variety. Does anyone know the pros and cons of handmade glair vs. commercial glair?

Thank you in advance for your help.


Vandlized Painting

Question asked 2019-03-20 15:19:08 ... Most recent comment 2019-03-20 17:25:32
Art Conservation Topics

​I have a painting when my apartment whas broken into they spray painted a Texas longhorn emblem on it, I believe the painting is acrylic can the spray paint be removed and not destory the painting?

Whiting for Gesso

Question asked 2019-03-19 15:28:02 ... Most recent comment 2019-03-20 12:09:16
Chalk Egg Tempera Grounds / Priming

Over the years ​I've tried various chalks (calcium carbonate) and gypsum (calcium sulphate) to make gesso. I've come to prefer a fine marble dust, for hard to define reasons: it's a bright white, has the right "feel" of hardness to me, and admittedly I probably like the idea of working with ground marble.

Within the two general categories of chalk and gypsum there are many different products available, differentiated by source, type of grinding, processing, natural coloration, etc.  Is it correct to say that these properties don't affect the quality of the gesso, rather they merely reflect individual artist preference (such as my own mentioned above)? Are these differences actually perceptible (aside from the obvious visual one of coloration)?  

Finally, is there any reason to make a egg tempera ground (final layer, not initial) using a medium or coarse grind chalk or gypsum, or would that increase porosity/absorbency too much?


Koo Schadler

Damir Pusic

Question asked 2019-03-18 10:00:33 ... Most recent comment 2019-03-19 09:21:21
Varnishes Studio Tools and Tips Health and Safety

​Hello MITRA,

How long it takes for turpentine to evaporate from a freshly applied layer of dammar varnish over an oil painting with dimensions 80X60 cm?

I plan to invest in local exhaust ventilation (LEV), so it would filtrate varnish vapor. In this process I would varnish painting inside a LEV hood. I don't konw how long to keep it inside.

Kind regards,

Damir P.

Cradling large, rigid, synthetic supports

Question asked 2019-03-12 15:01:32 ... Most recent comment 2019-03-15 15:43:16
Rigid Supports Oil Paint Industrial and Non-Traditional Products Alkyd

I'm considering using either PMMA or a composite panel for an oil painting (using alkyd medium). I expect the size to be around 100 by 70 cm, possibly a bit smaller. In order to keep the weight of the panels manageable, I don't plan on using PMMA thicker than 4 mm (the composite panel will be 3 mm). I understand that this should be cradled somehow on the back? Or would a solid frame with back supports suffice?

On that note, is there a general rule for how large a panel can be, given its thickness, before it needs some sort of cradling?

Oil paint becoming transparent over time.

Question asked 2019-03-14 00:55:45 ... Most recent comment 2019-03-15 01:24:15
Drying Oils Oil Paint Pigments Technical Art History

​I'm wondering if the mechanism for oil paint becoming more transparent over time is well understood?

More specifically, if I paint a layer of paint over another layer, will they both become more transparent at the same rate, or will the top layer become transparent more quickly?

I know some pigments will fade more quickly than others, but for simplicity, let's make the pigments in both layers identical.

Alizarin Orange lightfastness confusion

Question asked 2019-03-13 19:43:15 ... Most recent comment 2019-03-13 22:21:37
Pigments Oil Paint

​Hi! I love Williamsburg Oils’ color they call Alizarin Orange but I’m confused about why its lightfastness rating is Fair, when the pigments it consists of are rated as Excellent by Gottsegen. It consists of PR 177 Anthraquinone and PY 83 Diarylide Yellow HR-70. Bound in alkali refined linseed. Both PR 177 and PY 83 are rated as having “excellent” lightfastness in oil by Mark David Gottsegen in his book. Who is correct?

I typically use this color by itself in thin glazes but sometimes in tints with titanium white or mixed with other transparent warms like quinacridones.

Preserving kraft paper, construction paper, and other non-archival papers

Question asked 2019-03-10 10:16:02 ... Most recent comment 2019-03-10 21:18:12
Chalk Flexible Supports Pastel

I have tested some kraft paper (the brown one used for packing) and construction paper and concluded that the surface works really well for drawing, even better than some art papers. I tested them and it appears both have good pH, but I know that they will probably still deteriorate with time.

I read in the Flexible Supports advice that paper can be attached to a rigid support to preserve it for longer, and wanted to make sure  whether this applies to all papers, including ones not strictly intended for artist use?

My plan of securing them would be: attach the paper to an HDF or hardboard cut to a slightly bigger size using a heavy acrylic gel (or acrylic gel medium) spread on the board surface, remembering to press the paper so that there are no air bubbles/creases formed. I know that the paper will likely still discolor, but I don't mind that. Considering the durability of acrylic, I would expect the drawing to last indefinitely in the right conditions, since even though the paper would become brittle, the strength of the acrylic medium would hold it together. Can anyone knowledgeable about this subject comment? Should I be worried about pigment discoloration, if I plan to use lightfast pigments like charcoal, sanguine and white pastel?

archival adhesive wood and paper

Question asked 2019-03-08 12:53:00 ... Most recent comment 2019-03-08 14:46:10
Animal Glue Art Conservation Topics

I am looking for an archival glue for adhering wood to paper that dries fast. I am using small pieces of wood to make an armature for paper for a diorama. I had been using an archival hot glue but it seems too brittle and will not hold the individual pieces to the wooden box they are going in to.  

Safflower oil on rigid panels

Question asked 2019-03-05 19:00:19 ... Most recent comment 2019-03-06 15:54:53
Paint Additives

​ I'm trying to evaluate the degree of risk associated with inluding one frequently used colour bound in safflower oil (a white paint for example) in a palette where the rest of the colours are bound in linseed oil and the paintings are on rigid panels.  

Your document on mediums states that paints bound in safflower oil yield a "slightly weaker film" than those bound in linseed oil.   I can see how this would be an issue when painting on stretched fabric where the paint needs to withstand flexing but is this less of an issue when painting on a rigid surface?    

Secondly, colours are rarely used without being mixed with other colours. If only one of the paints on the palette contains safflower oil does that also reduce risk?  

Sealing Panel Edges

Question asked 2019-02-25 12:14:22 ... Most recent comment 2019-02-25 21:50:34
Rigid Supports

​My Mt. Athos friend has another question. 

The icon workshop seals all sides of their wood panels with Lascaux Varnish (which I believe is B-72); 3 layers on front, 2 on back and sides.  They do this as the last step.  Is there a preference as to when sides and back get sealed (i.e. when the panel is first made, or when the painting is finished)?  And does B-72 protect against  humidity as well as an oil based paint?  



oil based spray paint

Question asked 2019-02-22 13:02:50 ... Most recent comment 2019-02-22 17:38:38
Oil Paint

​Hi There, I'm a painter and am looking to incorporate spray paint into my paintings. I usually paint in acrylic first then oil and would like to be able to paint with an oil based spray paint in the upper layers of the canvas. Do you know what the longevity or archival nature of using a oil based spray paint or enamel might be? what changes or adhesion issues might i run into using a product like rustoleum? is it a big no-no? should I try using high quality oil paints via an airbrush instead? Thanks!

Seeking a way for painting to be fun again: ok to mix walnut alkyd with stand oil and OMS?

Question asked 2019-02-20 02:18:13 ... Most recent comment 2019-02-22 03:42:35
Oil Paint Paint Mediums Alkyd Drying Oils

Dear MITRA moderators,

Due to my painting style, I need a medium that will enable me to blend my initial wet-in-wet oil layers the next day. Like many, back in the day I used the old painting medium mix of 1/3 each dammar varnish, linseed or stand oil, and artist's rectified turpentine. Needless to say, once I learned of the longevity pitfalls with dammar varnish, it has been in my rear view mirror. I also switched from turps to odorless mineral spirits. I do miss the "buttery feel" of how the paint moved when I used the old 1/3's mix.

I started using walnut oil several years ago when I was told that it yellowed less than linseed products. When I learned that alkyd oil mediums are recommended for the greatest longevity, I tried one, but it dried way too fast for my technique, getting quite gummy both in the brush and on the panel before the end of my painting session. I then tried the walnut alkyd, which I greatly prefer over the other alkyd medium brand due to the slower drying time, but it also gets too gummy and isn't reliably blendable the next day. (I do mix a touch of OMS with the walnut alkyd, which works better than the straight product for me.)

Additionally, with both the walnut oil medium and the walnut alkyd medium, I find each layer to be a weak paint film when dry to the touch or even "bone dry". I have read similar comments about walnut oil's weak paint film on other MITRA posts, though the manufacturer has assured me that it will get stronger with age. However, my periodically slightly vigorous application or removal technique when painting indirectly with subsequent layers has meant that sometimes I inadvertently bite into the previous layer, so I'm also looking to strengthen my painting medium. 

Chemically, I know that walnut oil and stand oil should be compatible, but would it overly complicate the structure to put a few drops of stand oil in with my walnut alkyd medium – or at least the last couple of fatter paint layers? Are the benefits of alkyd oil painting mediums so great that it would outweigh any such complication, or would it be better to return to a slower-drying oil medium mixture – but without the dammar varnish? 

I want to make painting fun again like it used to be! For me, this means paint that flows and moves, doesn't dry too quickly, and makes a strong paint film so that I don't have to worry about removing the previous layer when cleaning up the edge of a newly applied stroke. It also means that I can rest easy knowing that I have done my best to create works with the greatest chance for longevity.

I appreciate any information or advice you can impart. Thanks very much!

Inner Glow panels

Question asked 2019-02-20 11:53:31 ... Most recent comment 2019-02-21 13:38:18
Rigid Supports

​Has anyone used Inner Glow panels?  Does the wood check or split or has it been properly seasoned?  thanks so much.

Mounting canvas and paper to wood panels

Question asked 2019-02-11 15:39:36 ... Most recent comment 2019-02-16 11:41:10
Sizes and Adhesives Grounds / Priming Rigid Supports Flexible Supports

​Hello dear people from MITRA.

I wanted to ask some questions regarding mounting on wood panels.

1. Do you think that 9mm birch plywood is ok to use as a base for mounting  canvases, papers?  If not, what kind of wood do you think is better to use as a base for mounting?  

2. Before mounting a canvas/paper to wood, do you think that wood should be sized with something? And if you do, with what kind of sizer? 

3.When mounting a linen canvas/paper what kind of glue should i use? I have heard people using Golden Soft Gel as a glue for mounting canvases/papers , or some kind of PVA glue...? 

4. Do you think that this practice of mounting canvas/paper on wood panel is archival? 

Thank you

Marko Karadjinovic

archival affixitive?

Question asked 2019-02-13 12:53:41 ... Most recent comment 2019-02-13 15:27:43

​If there an archival way to affix pastels?

titanium-lead white paint mix

Question asked 2019-01-30 12:33:30 ... Most recent comment 2019-02-11 15:25:44
Oil Paint Pigments

​As I reach the end of my titanium white supply, I am revisiting the decision to again mix a 50-50 lead-titanium white for painting.

Titanium white gives a greater opacity over time, but my understanding is that it creates a "softer" paint film.

Lead carbonate white has less opacity, but creates a stronger, harder paint film.

I mix them to hedge my bets with some of the good properties of both.

As I now paint almost exclusively on 10 mm, honey combed, aluminum panels, which will not bend , expand, or stretch like stretched linen, how important is it to have a "strong" paint film?

As I am now using a 25-75 walnut alkyd-OMS medium, is there enough strength and flexibility provided by the alkyd to eliminate the lead carbonate?

I tryi to keep things simple and the paintings "permanent" and when there is an opportunity to do so, I question my methods and materials.

Thanks for your help,


PS   Not sure that I can do anything more to provide permanence in my paintings.   Painting on panels is a biggie.

limestone and plant glue

Question asked 2019-02-10 05:29:14 ... Most recent comment 2019-02-10 15:12:52
Grounds / Priming

​I am looking into using a gesso consisting of French marble dust, limestone powder, titanium dioxide pigment and plant-based binders (Methyl Cellulose).  Or one with just the limestone and methyl cellulose. (I am unsure of the ratios because the powders come premixed)

I have a few questions:

Are there any conserns to consider about any of the ingredients, soaking up, cracking, archival etc.?

Does anyone have experience using a type of alternative gesso like these?

The gesso will be used as a ground and primer for streched linen canvases, applying 2-3 coasts. 

Reason for this type of ground: looking for a nontoxic enviro friendly option. An alternatve to acrylic, PVA or rabbit hide options.  

thank you in advance for your time

Another Mt. Athos Icon Question

Question asked 2019-02-06 17:36:32 ... Most recent comment 2019-02-10 11:14:43
Art Conservation Topics Egg Tempera

Hello Mitra,

Among the questions the Mt. Athos iconographer sent me, what follows is the most vexing.  It is also very complicated.  His email explanation was very long, so I have extracted the main points below.  

The Problem

The workshop has a large icon production, each monk using same materials and procedure.  About 3 years ago some icons appeared "faded" (not sure if icons are literally losing pigment particles or pigments losing their color).  See images, attached.  On left, icon in good shape; right, icon with diminished color.   He says they appear worse in person.

Mt. Athos Icons, 1.pngMt. Athos Icons, 2.pngMt. Athos Icons,3.png

- The color change takes place within 3-6 months after completion. 

- Does not occur on all icons

- Occurs on both unvarnished and varnished icons.   

- Occurs mostly on large icons.

Materials & Methods of Workshop

- Use Cedar Wood Panels

- Traditional Gesso with 100-300 bloom strength glue

- Use pigments that are, in his words, "dried out, old, cheap"

- Use premade (by the monks) mixes of 6 to 8 pigments for flesh and other areas

- 1 part egg to 1 part vinegar medium

- Hard, tap water to thin paint

- Would often thin tempered paint with water considerably

- Finished with Lauscaux Acrylic Varnish

- Very humid environment


In an effort to solve the problem, they made the following changes:

- Replaced all pigments with new colors from good companies

- Simplified premixes of color to just 2 pigments (i.e. flesh = Iron Oxide Yellow from Schminck, Eisen Oxide Orange from Kremer)

- No vinegar in medium

- Replaced tap with distilled water

- Not thinning tempered paint with water anymore

Once they made the above changes, the problem decreased 80% but is not entirely gone.  

My Comments

I have a few comments on their practices:

- Use a 450 bloom strength, 100% collagen glue in gesso.

- If working with pigment pastes, be attentive to the potential for mold (i.e. if pastes are partly drying out & sitting for a while)

- Pigment age isn't an issue (they don't become "old") unless they are (a) in a hydrated/semi-moist state (can cause mold), or (b) a fugitive color, which can be affected by UV light (work with ASTM Rated III colors).

- A "cheap" pigment isn't necessarily bad, many earth colors are very inexpensive.  However important to buy from a reputable supplier of artists pigments that can give specifics (origin, lightfast rating, toxicity, etc). 

- Complex premixes of color are fine.  However greater complexity  in a system = greater chance of problems, harder to diagnose source of problem.  Nonetheless, doesn't mean a complex system can't be successful. 

- Mineral pigments are most stable.  

- Vinegar can act as a preservative but it's acidity may affect some colors.  Better to nix vinegar and just start with fresh egg (as they are now doing).

- Once paints tempered properly (correct ratio of yolk to pigment) can thin tempered paint with more water to affect working properties.   In fact, would be unnecessarily very limiting to work only with paint of all the same density.  

However, if you significantly thin tempered paint with water, at some point the binder (egg yolk) is so dispersed, that it becomes necessary to add a drop or more yolk medium to paint. There isn't a precise formula for when more yolk is needed in very water-thinned paint, more of a feeling; i.e. when paint feels like watercolor instead of a bodied, egg-based paint, add bit more yolk to the paint. 

Explanation for Changed Colors

While I think the icon workshop could (or already has) improve some of their practices, none seem to explain the change in appearance of the icons.  I don't even understand what's happening to the color!  Given that some varnished icons faded as well, I don't think they could be literally losing pigment (as a varnish wouldn't permit that); it seems more likely pigments are losing color.

The two things that strike me as potentially problematic are (a) the high humidity in their region, and (b) the cedar panels.  I was struck by the response to an earlier question I posed which mentioned VOCs emitting from cedar can affect metallic colors - might the VOCs be turning some pigments transparent?  If so, why some icons but not all - different wood & atmospheric conditions? 

So I'm puzzled by his dilemma and welcome any ideas.  I also welcome response to my comments to the workshop to improve their practices.  


Koo Schadler

Cedar Wood

Question asked 2019-02-02 13:17:56 ... Most recent comment 2019-02-06 17:37:35
Rigid Supports

My Mt. Athos correspondent says the monks work on cedar panels. I suspect they work on cedar because the wood is insect and rot resistent, but are there consequences to the resins in such a wood?  Cedar takes staining very readily; does this mean it's especially porous and thus more vulnerable to absorbing RH?  Any more thoughts on the pros and cons of cedar as a painting support, specifically cedar coated with traditional gesso?


Koo Schadler


Question asked 2019-02-06 08:55:15 ... Most recent comment 2019-02-06 14:48:52
Paint Mediums Solvents and Thinners Oil Paint

​One of my colleagues used to use Laropal K80 for making his own painting medium. This product, however, is replaced by Laropal A81 for some time. But using this new A81, the ratio laropal/white spirit seems off, it turns into a tough sticky substance. Does anybody here, know what the ratio should be, or how to avoid the gunk?


Rabbit Skin Glue

Question asked 2019-02-02 12:27:08 ... Most recent comment 2019-02-03 07:57:52
Animal Glue Grounds / Priming


I recently received an email from a monk living on Mt. Athos; he works in the Iconograpy department.  He has many question, including trying to address a recurring problem with their icons.  I'm in the process of editing his query to a manageable size.  Here is the first of several questions from him that I'd like to pose to MITRA:

Is the most important thing in a gesso glue that it is genuine collagen and good quality, or that it has a high bloom strength?  We are currently using Lucas brand, bloom 100-110 and 180-200.  I understand that the recommendation for gesso is 450 bloom. So can RSG be good quality but also a lower bloom? 

Thanks for helping me to help the Mt. Athos monks.

Koo Schadler

Dipropylene glycol as an oil paint medium

Question asked 2019-01-30 22:50:10 ... Most recent comment 2019-01-30 23:22:22
Oil Paint

​Maimeri makes a product called Eco Oil Medium. Looking up the SDS, it is 100% Dipropylene glycol (DPG), readily available from hobby cosmetic suppliers. It seems to have a good safety profile.  It sounds like it would replace the use of a drying oil as a medium, with lower viscosity (described by one user as watery). I might find the Eco Medium preferable if it doesn't cause yellowing or longer drying times, as oil mediums can.  Is anything known about adding dipropylene glycol to oil paint?  Should it be considered experimental?

Alkyds and varnish

Question asked 2019-01-28 06:48:52 ... Most recent comment 2019-01-29 17:03:16

I read in another post that "Alkyds dry quick to the touch, compared to oils, because of the long polyester polymeric chain component to them." ... but   

"After this first drying step, they dry much like traditional oil paints, which is by auto-oxidation and cross-linking.  So, they dry to the touch faster, and can get ‘stiffer’ faster, compared to oil paints, because of the polymer component, but they eventually dry in a similar fashion to oil paints."

 The key advantage of alkyds then seems to be that they quickly provide a touch dry layer that can be painted over. However, am I correct in assuming that paintings done using alkyd paints and mediums still come under the recommneded 6 to 12 month drying time before varnsihing. 

Old acrylic painting on canvas

Question asked 2019-01-24 08:10:00 ... Most recent comment 2019-01-25 07:31:19
Grounds / Priming

​can I use oil primer over an old acrylic painting to then paint a new work in oils

How to frame a painting on panel without using screws?

Question asked 2018-11-07 14:46:31 ... Most recent comment 2019-01-25 00:30:05
Acrylic Rigid Supports Art Conservation Topics


I am working on a painting (acrylic) on heavy plywood (about 2cm thick). It is 48x48cm. I would like to frame it when it's finished. But I am worried about using screws. Is there a way to frame that painting without making holes in the back? Also, the whole picture should remain visible so I can't press its edges on the front against the frame... 

Thanks a lot for your help.

Best wishes.


Relative Humidity specifics

Question asked 2018-08-12 05:50:43 ... Most recent comment 2019-01-24 04:44:57
Environment Flexible Supports Storage Rigid Supports Oil Paint

​Dear MITRA moderators and community,

First of all, thank you so much for your time and expertise. I really appreciate this valuable resource that you are providing.

My question is about relative humidity, and its potential impact on artwork, particularly on oil paintings. I have read your very informative pdf about artwork storage and whatever else I could find here or elsewhere about the issue, but did not see specific information as to what specifically constitutes "wide swings" or fast changes in RH.  Would this be something really quite drastic, such as leaping from 35% to 85% in 30 minutes, or does the phrase refer to more numerically subtle conditions, such as 55% to 65% within 24 hours?

Since late May or early June, I've been experiencing humidity issues in my rented studio space that I definitely did not have last summer. I have a combined thermometer/hygrometer there as well as in my home studio. At the start of this, I was experiencing high humidity levels in the rented space of 70-75%, and even discovered some brown drips down one of my interior walls!  

My landlord has been very responsive, and after fixing an air duct leak that had caused the brown condensation drips, he purchased a small dehumidifier for me to use. I know to avoid "wide swings" or fast changes in humidity, so hopefully I stepped it down slowly enough at first. While I was initially pleased that the dehumidifier unit has manual settings and three fan speeds to facilitate a slow change, unfortunately it just can't maintain a steady humidity -- I am usually still getting 10 or more percentage point swing each day. The daily temperature has remainded constant -- 70-72F.

The supportive landlord is now making several changes and improvements to the property, including sealing my two exterior brick walls from the outside, as well as underneath my concrete floor from the basement, which will all hopefully contribute to a more managed interior climate.  In the meantime, is a daily swing of 10% considered a "wide, fast spread"?  My target is to get it down to 50% RH, but after a spike, I am setting it for 60 then 55 in an attempt to walk it slowly back down again.

I wonder if bringing the oil paintings back to my admittedly overcrowded home studio would be a better temporary storage solution until the landlord gets this under better control. I do have client and curator studio visits in the rental space, so moving the oils isn't the ideal solution for other reasons, but the longevity of my work is of greater importance to me. The paintings that are hung on the two exterior brick walls (unavoidable since it's not a cavernous space) have blueboard backings. The only deformations I have found are on some studies done on small, flat panels that have no cradling. (I have already spoken with the Ampersand representative on how to handle that issue.) I have both oils on stretched linen and oils on cradled Gessobord panel in the space, both finished and framed, as well as in progress. I also have works on paper (framed and unframed) and framed photography in the space.

I appreciate any further specifics you can provide on what exactly a "wide, fast" humidity spread would be in 70-72F, and whether it would be better to safely pack up the paintings and bring them home for now.

Thanks again!

Polyethylene foam as a frame-padding material for wood panels?

Question asked 2019-01-17 15:25:23 ... Most recent comment 2019-01-19 18:37:32
Matting, Framing, and Glazing Rigid Supports Oil Paint Art Conservation Topics

​I've been trying to come up with a better way to frame oil paintings on (solid, uncradled) wood panels. My current thought is: 

1. Construct the frame to allow for the appropriate amount of room for expansion within the rabbet. Fill the voids on the sides of the panel with a polyethylene foam (e.g. EthaFoam, Volara, Cellu-Cushion). 

2. Cut a large piece of polyethylene foam to fit behind the panel, filling the rabbet flush to the back of the frame.

3. Screw a piece of 1/8" plywood to the back of the frame to hold everything in place. 

Basically the panel would be surrounded, sides and back, with foam that would hold it firmly in place and keep it centered in the frame, while also not restraining the panel, so that it can move in response to changes in humidity. 

Is this a sound approach? Is a polyethylene foam material like EthaFoam a good material for this application? 



Water gilding over oil gilding

Question asked 2019-01-18 19:13:47 ... Most recent comment 2019-01-18 19:35:41

​I applied an oil gilding, which is now perfectly dry.

I've changed my mind, as I feel that some areas should be burnished to a high gloss. Can I apply red bole over this and water gold it on top of the matt gold of the oil gilding?

Thank you 

ABS PLASTIC-Acrylonitrile Butadiene Styrene as Painting Panel

Question asked 2019-01-10 14:14:15 ... Most recent comment 2019-01-17 14:02:10
Industrial and Non-Traditional Products

​After reviewing MITRA's rigid supports, I could not find any mention of ABS. A very accomplished and highly regarded oil painter (portraits/figurative) has recently begun using ABS for painting panels. The panel is lightly sanded and painted on directly with the oils. The painting surface is very smooth but has tooth after light sanding. How is ABS as a painting panel, if the thickness is similar to ACM thickness? Question- 1. ok to paint on directly with oils or casein or acrylic paint as one professional artist does? 2. ok if primer is used 1st? which primers? 3. ok to adhere canvas to? Here is a link that describes ABS very well. I had no idea that ABS is what Legos are made of!  "ABS is exceptionally resistant to chemical degradation, either by alkaline or acidic agents."

Golden Black Gesso and Egg Tempera

Question asked 2019-01-13 17:20:53 ... Most recent comment 2019-01-17 12:16:32
Grounds / Priming Egg Tempera

​I just completed a metalpoint drawing on Golden Black Gesso.  I applied egg tempera (fairly densely painted, in multiple layers) on a portion of the drawing.  It's been my experience that egg tempera behaves best and ahderes longest on grounds with a lot of porosity, so that mechancial adhesion can take place; and for this reason I don't generally work on synthetic polymer grounds unless they have a lot of added solids and extra absorbency.  The egg tempera behaved pretty well a top the black gesso (a bit more sensitive to lifting, but not too much), so I'm wondering about the composition of the ground. Is Golden's black gesso high in solids, and/or considered more absorbent than regular acrylic gesso?  Has Golden (or anyone else) done testing of egg tempera on black gesso, to see how well it adheres in the long term?


Koo Schadler 

Humidity in Studios in Apartments

Question asked 2019-01-11 07:48:39 ... Most recent comment 2019-01-13 20:17:27
Storage Environment Studio Tools and Tips Scientific Analysis


I have been thinking of asking this question for a long time, and have been reading about average and recommended humidity levels, but since my studio is in my apartment where i live, and we have radiators in every apartment in the building i find it very difficult to set humidity that is recommended...

During the spring, summer and even some parts of autumn the humidity is usualy about 40-55 % . I have read that these are actually solid, ok humidity levels.

But during the cold autumn days and during the whole winter, the city starts turning on the heating and the radiators begin working. 

Temperature is usually set in whole building, so in every apartment is pretty much the same temperature, around 25°C . 

Then the humidity levels drop  up to 12-22 % . 

I was really worried when i saw that the humidity drops up to 12%. 

I wanted to ask, do you think that low humidity like this represents a big danger to paintings( oil, acrylic, egg tempera) and watercolors, gouache paintings, also drawings....?  

If it does, how can i fix this problem..? 

Or are these strict rules meant for very old artworks that need extra museum care..? 

I try to do best for my artworks, and to take care of them as much as i can, but whenever i start worrying that much, i cant help but to think how many old artworks survived in old houses, old studios, in some military storages during wars, and back  in ancient times when i believe artists didn't knew much, or maybe anything about humidity levels...? 

Your answers are much appreciated!

Thank you!

Marko Karadjinovic

Stone or Mineral paper as painting surface

Question asked 2019-01-09 15:08:44 ... Most recent comment 2019-01-12 15:22:36
Industrial and Non-Traditional Products

​The papers in question are made of calcium carbonate with a binder that makes it into a beautiful vellum smooth absorbent surface. I have used this paper with casein paint and casein as underpainting with subsequent alkyd/oil paint layers. I first adhere the unprimed mineral paper to sanded ACM panel using acrylic gel medium or lineco. Since paper is just calcium carbonate with a binder, wonder about the longevity of this paper? papers by Mitz or Yasutomo companies. Acid free. Mineral paper also handles well for acryl gouache.

Fresco Colors

Question asked 2019-01-10 08:22:53 ... Most recent comment 2019-01-12 08:22:33
Pigments Mural Painting

​Does anyone know of a website or book that offers a complete list of pigments suitable for fresco?  The lists I find online are oriented towards historic fresco colors, or mention just a few modern colors.  I'm looking for a more comprehensive list.   


Koo Schadler

Any issues with using pure Lamp Black (PBk6) with oils?

Question asked 2019-01-10 16:20:52 ... Most recent comment 2019-01-11 04:25:07
Art Conservation Topics Oil Paint Pigments Scientific Analysis

​Hi all,

I was wondering if you had come across any issues with using Lamp Black (PBK6) in an allla-prima situation (no underpainting), when not mixed with other pigments or thinned with solvents? 

I paint on ACM panels over a toothy clear gesso (silicia) which is much less absorbant than white gessos. I don't use zinc in my paints or in a primer/gesso.

I use walnut oil to thin out my paint and I normally use Mars Black (PBk11) for my darkest blacks. I would like to try using Lamp Black instead as it should be a bit darker and have a longer drying time which I prefer.

However I have read that it doesn't form very strong paint films and I am concerned that it would form a weak paint film when used on its own and may lead to cracking in the future?

Has any studies found issues with Lamp Black in oil paintings when used in pure black areas?

Thank you,

Mixing Acrylic Mediums

Question asked 2019-01-07 08:10:21 ... Most recent comment 2019-01-10 19:16:59
Acrylic Paint Mediums Paint Additives

​Hello and happy new year to all!

I have question about Acrylic mediums.

I am painting with Liquitex Heavy Body and W&N Professional Acrylic colors. 

I did a painting using Liquitex Gloss Medium/Varnish (Which people from Liquitex told me that it is best to use it as a medium) . 

At the end, i wasnt happy with the results and i basically took other medium, LeFranc & Burgeois Acrylic Fluid Matte Medium (Since i liked the results more with it) and repainted the whole painting to something completely different.

In this process i wanted so badly to make something that i will be happy with, that i didn't pay attention to what was on my pallette. So i accindetally mixed small amounts of previus medium (Liquitex Gloss medium/varnish) that was in some of acrylics, with this LeFranc Fluid Matte Medium. 

I have heard that if i did something wrond it would be shown in few hours with acrylics? 

I think that this is the painting that i will be happy with, so before i continue, i wanted to ask what do you think? 

Did i make a big mistake in accidentally mixing small amounts of Liquitex Gloss Medium/Varnish with LeFranc Burgeois Fluid Matte Medium, because colors that were on pallette had small ammounts of both mediums in them...? 

And is it a bad practice to switch from one medium to another on a single acrylic painting...? 

Your answers would mean a lot!

Kind regards.

Marko Karadjinovic

Plywood support with traditional gesso

Question asked 2018-12-27 21:19:28 ... Most recent comment 2019-01-10 18:22:41
Rigid Supports Grounds / Priming

​I am currently working on birch plywood cradled panels that I have first sized on both sides with 2 coats of GAC 100, then applied thin layers of traditional glue gesso for painting in casein and oil. In a couple of the paintings I have seen a few areas of short parallel cracks coming through, and am considering adding a layer of thin fabric to the preparation process. Before I get in too deep with preparing a bunch of these panels, I'll appreciate some advice on 1.) the best material or materials to seal front and back of panel, and is the GAC 100 OK for this; 2.) best adhesive(s) for attaching fabric (I've used acrylic gloss medium for this in the past, but have had hide glue suggested to me as better).

OR -is there a way to avoid the fabric step altogether, and simply prepare the wood surface well enough to accept the gesso? It seems like I've read various opinions on this and am now pretty confused! Thank you for your help.

Regalrez 1094 varnsihes

Question asked 2019-01-09 11:54:24 ... Most recent comment 2019-01-09 16:43:11

​There seems to be a growing belief among painters and art teachers as to the 'miraculous' qualities of varnsihes based on Regalrez 1094. The most common belief seems to be that the full strength commercial varnsih can be safely applied when a painting is touch dry. Contrary to that, one vendror recommends the fingernail test which, in my testing takes anywhere from 2 to 4 minths to give the green light, depending on the number of layers of paint (overall thickness).  Another vendor recommends sticking to the tried and true 6 to 12 months.  To complicate this there is also some advice to thin a Regalrez varnsih with a solvent and use it as a retouch varnsih on touch dry paint.  Can you comment on this? Is a Regalrez varnsih differnt enough that the rues for varnsihing change? What are the risks of varnsihing too soon with a Regalrez varnsih?

Spots on Oil Painting

Question asked 2018-11-28 12:33:33 ... Most recent comment 2018-12-31 16:02:26
Oil Paint Solvents and Thinners

​Anyone know what these spots could be that are showing up on my oil painitng? I normally stain the canvas, but this time I opted to paint right on the white gesso. I did just clean my paint brushes, so worried maybe they werent all the way dry? I am using Geneva Oil paints and I used some Neo Megilp to cover the sky area. I can blend these out but then they show back up the next day. Any advice on how to remedy this is much appreciated! One picture is a close up of the problem area, the other is the whole painting, thought I find these mostly on the left side I have spoted a few in the lighter areas to the right. Screen Shot 2018-11-28 at 12.30.41 PM.png

Screen Shot 2018-11-28 at 12.30.56 PM.png

Canvas not adhering to panel

Question asked 2018-12-26 17:34:07 ... Most recent comment 2018-12-26 19:42:57
Oil Paint

​Attached are 2 photos. The first is my painting showing buckling. At first, it wasn't this bad. The canvas is Raphael zinc free on a professional art panel from NY Central art supply. The bucking started almost immediately after I finished the painting. The second is the product I used to fix the edges. Ultimately, it didn't work. The buckling has gotten worse even beyond the parts I fixed. Why could this have happened and how can I fix it so the integrity of the painting is restored? C9765112-BB82-43E4-BBF3-DEE492953D7F.jpeg B187BCB1-8686-4F96-BA7D-A0A049E40062.jpeg

Paper stuck to Acrylic Paint Film

Question asked 2018-12-25 16:26:08 ... Most recent comment 2018-12-25 18:31:20

​My cousin did a pair of acrylic paintings for my mother for Christmas, and wrapped the canvases with wrapping paper, with no intermediary layer (yeah, I know... yikes). Unsurprisingly, the paper stuck to the paint, particularly near the edges. I know acrylic films have a glass transition temperature that is pretty close to room temperature, and therefor there's always a chance that wrapping material will stick, even if the paint is well-cured. 

I've sent my cousin a link to where she can purchase glassine paper, but in the meantime, I'd like to take a shot at salvaging these paintings, if it's possible. This isn't the sort of thing that my mother or cousin would hire a professional to do--if they get ruined, then so be it. My cousin says she will repaint them, if necessary. 

So, conservators: if you were going to try to remove paper that is stuck to the surface of an (unvarnished, and also unsealed) acrylic painting, how would you go about doing it? Swab with some sort of solvent? Water? Something else?

Thanks! And Happy Holidays!  :)

Ralph Mayer's book...

Question asked 2016-11-07 22:12:01 ... Most recent comment 2018-12-21 21:51:34
Technical Art History Art Conservation Topics
I am wondering about the reliability of the information in Ralph Mayer's book the Painters Handbook? If not reliable and even if it is I would appreciate any and all recommendations.

Removing excess graphite with a kneadable eraser.

Question asked 2018-12-12 08:24:59 ... Most recent comment 2018-12-16 18:20:22
Drawing Materials Oil Paint Pencil

​I have seen people suggest using a kneadable eraser to lighten their drawings before painting over the top in oil paint, in a similar way to dusting off excess charcoal.
I would be concerned that the eraser could leave some residue.
Can I have your thoughts on this?

Ron Francis


Question asked 2018-12-16 08:21:42 ... Most recent comment 2018-12-16 12:55:46
Acrylic Alkyd Art Conservation Topics Handling and Transportation Paint Mediums Oil Paint Pigments Scientific Analysis Storage

​How important is a climate controlled vehicle for transporting oil and acrylic paintings? 

How can I Flatten out a wavy / buckled drawing paper?

Question asked 2018-12-15 16:34:01 ... Most recent comment 2018-12-15 20:28:42
Drawing Materials

​Hi all,

I have large 30 X 22 inch sheets of new Canford Cardstock 300 gsm acid + lignen free paper that has areas of waviness / buckling throughout the paper.  These papers are new and have no drawings on them.  I am looking for a solution to flatten the paper back out if this is possible?  There are no creases, just curvy waves.  Any help would be greatly appreciated.  


Metalpoint Experiments

Question asked 2018-11-01 12:15:10 ... Most recent comment 2018-12-11 15:18:44
Drawing Materials

Hello All

I'm doing some metalpoint experiments and would welcome ideas and feedback.  

Test Panel 1

To test the value of marks made by 6 different metals on 18 different grounds (2 of which are paper: Plike and TerraStone).  Metal hardness will vary (pewter, gold, silver, copper, brass, nickel). 

The goal is to see (a) which grounds produce the darkest marks, and (b) how the marks age (I've heard from various metalpoint artists that marks tarnish/age differently depending on ground).

Test Panel 2

Apply different metal points to a single ground to show variety of metal marks possible.   Metals to include: lead, lead-tin, pewter, zinc, pure silver, sterling silver, argentium silver, gold (22K, 18K, 14K), aluminum, copper, yellow brass, red brass, bronze, nickel, platinum, bismuth.  (I have all but zinc, bronze, bismuth - still working on those...).   For applicable metals I'll try both dead soft and half hard.

Any ideas for other metals to try?

Test Panel 3

Test methods to speed up tarnishing using liver of sulpher, onions/garlic.

Any other tarnishing tricks?

Test Panel 4

Add abrasive fillers to ground to see how fillers affect mark making. I'll use either generic house paint or student grade acrylic becasue I'm presuming I can add 10-20% fillers to them and they'll still bind well - yes?

Among the materials I'm considering are....

    Titanium white

    Zinc white 

    large micron size pigments (lapis, natural earths, etc..)

    marble dust



    ground glass

    bone ash


I realize some of theses substance (talc, gypsum) might be too soft  to affect marks, but I'd like to see.  Are there other wild and crazy substances I should try, just for the heck of it?  

All comments are welcome.  Thanks, 



Gouache and Watercolor on Drawing paper?

Question asked 2018-12-08 05:32:27 ... Most recent comment 2018-12-08 14:50:33
Flexible Supports Gouache Drawing Materials Pencil Watercolor


As well as a lot of artists know, there are those moments of inspiration when we grab something that we have and express what needs to be expressed, not really thinking about technique, compatibillity of materials and so on...

Basically we do what me must, and worry afterwords. :) 

One of those moments for me was recently, when i did graphite drawing on Fabriano Unica Paper (which is 250 gr paper made of 50 % cotton and ideal for printmaking, graphite,charcoal) and painted over that with Gouache. 

Is it a problem to use water media over graphite and on paper that is not best suited for it, but rather for dry techniques, but it is 250 gr paper and is Acid Free ofcourse? 

Thank you!

Marko Karadjinovic

Oil seepage to surface of white oil paint

Question asked 2018-11-19 19:27:52 ... Most recent comment 2018-12-08 13:39:54
Oil Paint Other

​I am finding that after a period of about 1 year or more, surfaces where I have applied very thick areas of white oil paint have brown oil spots, as if the oil in the paint is seeping to the top. This may be due to the low quality of paint I’m using: Winton - or perhaps the kind of white: Titanium. In these cases I have not mixed any mediums into the paint. What is the cause, and can it be repaired? Can I simply paint over the surface with a higher quality white, and will that last?

Framing fresh egg tempera paintings behind glass

Question asked 2018-12-03 16:43:49 ... Most recent comment 2018-12-03 16:30:00
Egg Tempera


Can you advise if I am able to frame egg tempera paintings done on gesso panels behind glass within 2-3 weeks of finishing?  Ideally, I would like the works to cure for a few months before framing but due to time constraints, I may have to frame earlier.  I have read the post on glazing ET works previously mentioned on this forum, so am aware of the need for separators etc - but wanted to check whether there would be any unacceptable issues with efflorescence/mould if framing is done this early - & whether the egg is particularly fragile at this stage.  Many thanks.  Zarina

Gilding Oil Paintings

Question asked 2018-12-01 15:09:46 ... Most recent comment 2018-12-01 21:24:38
Oil Paint Gilding


I want to try using gold/silver leaf with oil painting (the composite kind, not the real kind), and I was wondering how I should do it? I've used it with acrylic before and just gilded over top of the paint, but my understanding is that you shouldn't gild over oil paint because it takes an extremely long time to try. 

Would it be best to guild the panel first after priming, and then seal it (with what?) and then paint over it?

I was going to try this approach:

1. Size panel with GAC 100

2. Prime panel with acrylic gesso or oil ground and let dry for a few weeks if oil, for 1 week if acrylic

3. Draw out composition with watercolour pencil and then gild the panel where I want the gilding with Speedballs liquid size

4. Seal it with speedballs liquid sealer

5. Let dry for a day

6. Begin painting

Gouache techniques

Question asked 2018-11-23 13:28:45 ... Most recent comment 2018-11-26 16:12:11
Gouache Watercolor Ink Pencil Varnishes Matting, Framing, and Glazing


I would like to ask multiple questions, since it is about mixing gouache with other techniques.

1. Since many say that gouache is basically opaque watercolor (with more gum arabic binder?), is there any proper way to use it with watercolor? For example, is it ok to paint first layers with watercolor and then to finish the painting with gouache? When switching from watercolor to gouache on the same painting, is there any right way to do it, or i just simply paint with gouache over watercolor? 

And is it possible to switch process, to glaze with watercolor over opaque gouache? 

2. When doing underpainting with Ink, and then painting over that with gouache, which type of Ink is best suited for mixing ink wash technique with gouache technique? And how much can Ink be diluted with destiled water? 

examples of this technique:

3. When doing a drawing with black chalk or graphite, and then doing wash with brown or black ink, and then painting with gouache on top of that, is there a right procedure to do it, or i just simply switch from one technique to another as mentioned above?  And, what type of fixative is best suited for preserving a chalk or graphite drawing beneath ink, and gouache? 

examples of this techniqe:

4. When switching the process and doing watercolor underpainting, gouache painting, and then adding chalk, graphite in the final stage of painting, is there some sort of varnish or fixative that is best suited, so that graphite/chalk would not be smeared over the painting? 

example of this technique (Graphite (Chalk?) was used in shadows and lines, in the final stage of the painting )):

5. Can gouache be mixed with acrylic painting?

6. How should gouache, or mixed media (ink,gouache,graphite) be framed?   

Thank you in advance!

Kind regards.

Marko Karadjinovic

Sound and Toxin Free Oil Painting

Question asked 2018-11-25 09:24:23 ... Most recent comment 2018-11-26 12:39:49
Oil Paint Alkyd Grounds / Priming Health and Safety Rigid Supports Sizes and Adhesives Art Conservation Topics


I am re-reading my post of February 19, 2018,, and all the responses below it. As you know, I am hoping to work without toxins throughout my processes. I am seeking to know: can I create a stable painting without them? After laying out my specific questions for you to consider, I will describe my proposed modified approach, based on the answers you have given thus far.

Specific Questions:

Although lead white would add strength to the canvas, will the combination of my various processes create a more than adequate archival stability for my paintings over the centuries?


Can the rigid support (cradled panel) and the alkyd nature of my titanium white compensate for lead white usage in the ground and throughout my painting?

Can a traditional wet imprimatura compensate for the greater absorption of Golden Acrylic Gesso Ground? (I hope so - it seems to do a perfect job of it – performing for the artist during the process just as well as chalk gesso does – with perfect absorption level for the richer glaze layer and excellent surface flow for the subsequent lean paint).

Proposed Process:

  1.  Size a 16 oz. tightly woven raw canvas one side on the topside while fabric is flat on table. I prefer Gamblin PVA, for reasons already stated in a previous reply.  Snap the fabric when wet to work out any wrinkles. Let dry a day.
  2. Evenly stretch canvas over a birch cradled panel, with the weft direction being vertical for maximum long-term support. Use non-rusting strong thumbtacks for easy potential conservation adjustments if ever required.
  3. Rewet the stretched canvas after stretching with PVA if there are still any wrinkles to facilitate the pullout of the fabric. Let sit a day.
  4. Hand rub and sand five coats of Golden Acrylic Gesso Ground, slightly diluted for smooth application.
  5. Allow to cure over several days.
  6. With Gamblin Solvent Free Fluid, dilute Gamblin FastMatte Alkyd Safflower Oil Foundation paint (mostly Burnt Sienna) no more than 25%. Rub on a high paint spread imprimatura-priming glaze with a cloth.
  7. Into the wet glaze, drop an undiluted foundational layer (grisaille) using Gamblin FastMatte Titanium White and Burnt Sienna and Ultramarine Blue (mixed to the same colour as Burnt Umber). Let dry several days.
  8. With virtually undiluted Gamblin FastMatte paints, add another foundational layer (Velatura). Let dry several days.
  9. Add several layers, several days apart, each starting with a glaze or scumble of the same paints diluted with no more than 25% Gamblin Solvent Free Fluid, with high paint spread. Then modify the glaze with additions of slightly diluted paint, or in white areas, undiluted paint.      


Gamblin FastMatte Alkyd Safflower Oil Paints:

  • Titanium White
  • Burnt Sienna (in foundations)
  • Quinacridone Red
  • Hansa Yellow (in foundations)
  • Ultramarine Blue
  • Phthalo Blue
  • Red Transparent Earth (in glazing applications) 

Rembrandt Oil Paints

  • Transparent Yellow (in glazing applications)

I am looking forward to your answers. Thanks so much for all you do and for your clarifications here.

Kathy Marlene Bailey

how much of which varnish?

Question asked 2018-11-22 11:12:23 ... Most recent comment 2018-11-23 15:21:54

I have to varnish a big oil painting (200x370 cm), and I do not have a lot of experience with varnishing oilpaintings, to be honest. So I have some questions that I hope you guys can help me with.

-It will take quite some time to get the whole surface varnished, right? What varnish would give me enough time to work? (I'll ask two students to help me).
At the same time, the work is hanging in a canteen, so fumes should be not overwhelming for too long :-/.

-And how much varnish do I need for such a surface? The paint itself is rather smooth, but I doubt if 1 liter would be enough.

-And third, and last: we have to do this with the work standing, so not laying flat. How do I avoid dripping?

Thanks in advance,


What solvent removes old damar?

Question asked 2018-11-21 16:26:35 ... Most recent comment 2018-11-21 16:54:54

​New to Mitra.  So I am not sure how to use the search option.

How do I remove old damar varnish?  I tried using Turpentine, but it isn't removing the damar.  

sealing of charcoal on bristol

Question asked 2018-11-12 21:44:45 ... Most recent comment 2018-11-20 15:24:48
Drawing Materials

I would like to protect large charcoal drawings well enough to frame without glass (in a recessed frame). Not ideal, but the glass is an expensive and unwanted barrier. Perhaps Lascaux fix, multiple coats, then another acrylic sealer on top? Wax on top? Other artists must have solved this problem for large scale drawings?​ I have read everything under the category to date.

Difference between various odorless/low odor mineral spirits

Question asked 2018-11-14 09:05:36 ... Most recent comment 2018-11-14 08:31:00
Solvents and Thinners Oil Paint


I'd like to ask about possible differencies between various odorless/low odor solvents. I use Winsor&Newton Sansodor for cleaning brushes, sometimes to make mediums or dilute paint. I have some amount left but soon I will have to buy more. The price for 1 liter can in the shop from which I usually buy the stuff is cca. 32 Euro. That is not really cheap. Recently, I looked at Kremer pigmente and also asked them about their alternative and I was told, that it is Shellsol T. 1 l can is for 5,36 Euro. That is striking difference. So I've been wondering what is the difference between them - or between odorless solvents in general. I looked into MSDS sheets of four odorless solvents:

W&N Sansodor (

distillates (petroleum), hydrotreated light, CAS-No.: 64742-80-9, EC No.: 927-632-8

Schmincke Diluent N (

Substance 1: hydrocarbons, C4-, butadien-free: 50 - 100 %, CAS: 93685-81-5, REACH: 01-2119490725-xxx

Substance 2: hydrocarbons, C10-C12, isoalkanes, <2% aromatics: 10 - 25 %, CAS: 64741-65-7, REACH: 01-2119471991-xxxx

Gamblin Gamsol (

Naphtha (petroleum), hydrotreated heavy CAS: 64742-48-9

Kremer Shellsol T (

Hydrocarbons, C11-C12, Isoalkanes, < 2 %, 100 %, CAS-Nr not stated, EINECS-Nr: 918-167-1

If I consider just the term "odorless/low odor solvents", all these things should perform the same. But then I don't understand the difference in price. I guess, that various CAS numbers mean, that the composition is somewhat different in each case. Shellsol T is six times cheaper than Sansodor and Diluent N, but I suppose that doesn't mean that it is inferior product (and also I suppose Kremer wouldn't offer some sort of cheap "trash"). 

Can you explain meaning of those terms like hydrtretaed heavy, hydrotreated light, C11 (I saw msds of various solvents containing a range of these, like C11-C12, C9-C14, etc.)? How does it affect the nature and performance of solvent? Also, do you have any experience with Shellsol T in particular? What should I expect from it? If it performs that same as e.g. Sansodor there is no reason for me to go for Sansodor, which is six times more expensive.



Amber Varnish and Medium

Question asked 2018-11-11 16:22:57 ... Most recent comment 2018-11-11 16:20:00

​Wondering about the use of amber mediums and varnish in oil painting. Benefits, drawbacks? It is very expensive and Blockx is the only company that makes it at present.

Slippery nature of walnut oil

Question asked 2018-11-09 13:03:06 ... Most recent comment 2018-11-09 13:00:00
Drying Oils Paint Additives Scientific Analysis


Could someone tell me about why walnut oil has a slippery feel compared to other drying oils? Someone mentioned it's probably because of a higher glycerin content in walnut oil?

I have read someone else say that it's not recommended to all glycerin to oil paints though as it will interfere with the drying process?

Any thoughts on this?


Oil paint adhesion to acrylic primer

Question asked 2018-11-09 11:32:04 ... Most recent comment 2018-11-09 10:50:00
Grounds / Priming


  I'm trying to better understand my options for priming panels for oil painting and the pros and cons of each system. I was hoping someone could enlighten me with regards to acrylic primer. 

1. As I understand there are three mechanisms that enable adhesion of a new layer in a painting:   a) chemical bonding, b) absorption (wetting of the existing surface by the applied layer), and c) mechanical bonding (interlocking with rough/textured areas). Is this accurate?   

2. When applying the first layer of oil paint over an acrylic primer I assume that there will be no chemical bonding ? 

3. Acrylic grounds have calcium carbonate added to promote mechanical bonding. Is this intended to be the primary adhesion mechanism between the first layer of oil paint and the acrylic primer?

4. I've noticed that some brands of acrylic primer tend to be less absorbant than others - as evidenced by less sinking in of the first layer of piant. Also, "non-absorbant" acrylic primer has appeared on the market. It begs the question, what role does absorption play in the bonding of oil paint to acrylic primer?  Can too much absorption rob the oil paint of binder? Can too little absorption limit adhesion? 

Thanks in advance and I just want to say that this website and forum is a greatly appreciated resource! 

Bitumen/Asphaltum/Gilsonite Nbk6 pigment in oil paint

Question asked 2018-11-09 00:41:06 ... Most recent comment 2018-11-09 00:35:00
Oil Paint

​I asked about Bitumen/Asphaltum/Gilsonite at a painting techniques FB group. But, some warned that it is prone to cracking and fading in glazes. Although several manufacturers have paints named "asphaltum or bitumen" in their lineup ,they are NOT the traditional Nbk6 pigment but are various blends. One paint I bought was too reddish. The pigment alone is available from Natural Pigments and Kama pigments as gilsonite. The only oil paint I can find with solely Nbk6 bitumen is Maimeri Artisti. I would like to use this neutral transparent brown for glazing. But what about the fear of fading, cracking or some say darkening?

Magnesium Sterate

Question asked 2018-11-05 16:28:29 ... Most recent comment 2018-11-05 16:23:00
Paint Additives Oil Paint Scientific Analysis

​Hello all,

I was just reading an article from the UK art supplier (and manufacturer) about their own professional oil paint range:

In the article they show an example of the proportion or ingredients used and I was suprised to discover that instead of using Aluminium Sterate they use Magnesium Sterate. I have not heard of this before.. would I be correct in thinking it would work similarly to Aluminium Sterate but have a drying action?

I find their paints well pigmented, and good value for money, but too stiff and fast drying in some pigments for my personal tastes.

how to protect color of plants pressed on paper from UV ?

Question asked 2018-11-04 14:51:07 ... Most recent comment 2018-11-04 14:32:00
Art Conservation Topics Solvents and Thinners Pigments

I am currently working on a project in which I crush fruits and vegetables on Hahnemuhle cotton paper using a cylindrical engraving press. As the plants are emptied of 95% of their water in one pressure the color remains on the paper, it does not yellow for the moment, so I keep my print in the dark.

I would like to protect the color of crushed plants from sunlight, UV ... would you have an idea of ​​invisible lacquer, or colorless and matte varnish that I can pass on the plants without damaging or altering the paper?

I also thought of sticking a very fine paper, type rice paper 20 grams, on my print using rice glue or vegetable glue, to protect the plants (so they do not flake) and also protect them from light. When I do this the rice paper becomes almost invisible, I think that if on this paper I apply a layer of varnish to protect the colors from UV it would work, but what do you think?

I don't know what to use, do you have any idea ?

I have to find a solution to show the piece in February at an exhibition and I would like the colors of the fruits to be preserved  during the exhibition.

Thank you for your help

Robert Vickery

Question asked 2018-11-01 15:40:25 ... Most recent comment 2018-11-01 15:29:00
Varnishes Acrylic Art Conservation Topics

​I have a question about those paintings from artist Robert Vickery , that were done with acrylics. I have read that he used Liquitex colors, but what i am really interested is does anyone know with what type of varnish did he varnish those acrylic paintings, how those paintings look today? And are conservators able to remove this varnish and to clean the paintings without harming the acrylic beneath? 

Thank you!

Marko Karadjinovic

PW7 Zinc Sulphide

Question asked 2018-10-31 23:25:40 ... Most recent comment 2018-10-31 23:23:00
Oil Paint Pigments


Are there likely to be similar issues with PW7 in oil as there is with PW4?

Many thanks.

oil paint stick recipe

Question asked 2018-10-31 19:47:55 ... Most recent comment 2018-10-31 19:47:00


Affixed labels with fish glue

Question asked 2018-10-31 17:09:20 ... Most recent comment 2018-10-31 17:07:00
Sizes and Adhesives

​While getting ready for an upcoming show, I glued labels to the canvas backs of six of my works with fish glue. I like this glue because it is really tacky, dries fast and is reversible. To my utter horror I noticed that there is now a visible elevation the size of the label on the front of each picture. The paintings are oil on store prepped canvas. I did not add another layer of gesso before painting. Can I safely soak off the label on the back and perhaps dampen the unaffected area, or should I leave it alone and hope they don't get rejected. Any advise would be very much appreciated.

Final Varnish over Retouch Varnish?

Question asked 2018-10-29 12:12:45 ... Most recent comment 2018-10-29 11:59:00
Varnishes Oil Paint

Couple of years ago i have heard about this practice that is ok to put a coat of Retouch Varnish over a painting after a month/two months and then after a year-year and a half to put a final varnish on top of that.  

I heard that is especially ok to put retouch varnish  if the one needs to have a exhibtion, or has done commission and doesn't have year-two years time to let the painting dry.

Year ago i have contacted few companies and asked about this, and got the answer that is totally ok to put retouch varnish after a month/two months and after a year-year and a half to put final varnish on top of that, and that i don't have to remove the retouch varnish before applying the final one.

Also i have read that some conservators/restorators disagree, and that they think that the retouch varnish should be avoided, and that is best to put just a final varnish on a painting. If one needs to put a retouch varnish, then when he wants to put the final one should actually remove the retouch varnish before that??

What are your thoughts about this and what do you think is the best way to varnish a painting, and how to protect it if one doesn't have enough time to let it stay unvarnished for a year-two years?

Thank you in advance!

All the best!

Marko Karadjinovic  

Oil painting mediums

Question asked 2018-10-29 11:22:31 ... Most recent comment 2018-10-29 10:39:00
Paint Mediums Oil Paint Solvents and Thinners

​Hello! I have a few questions regarding oil mediums.

1. I have done some of my paintings with oil medium that has Venetian turpentine in it. The formulation of this medium is one part of stand oil, one part of Venetian turpentine (Schmincke Natural balsam/larch turpentine) and two parts of turpentine ( Lefranc & Bourgeois rectified turpentine) . I have read that Venetian Turp/Balsam is not that recommended, but at the time i didnt know, so i did some very important paintings with this medium. What are your thoughts about this medium? I was very carefull about layers ( fat over lean) Do you think that these paintings will be ok, even if i did them with this medium? 

2. I was also using Winsor and Newton Liquin Original medium.

What are your thoughts about this medium, do you think this is good archival medium to use?

And is it really true that you dont have to be that careful about "fat over lean" rule with W&N Liquin original? I always try to be careful about layers even with this medium. 

I wanted to ask is there some substance that can be added to Liquin as a thinner, some solvent, because i paint in several layers? Or i should just use less Liquin medium in first layer and then add medium as i build up the painting? 

Also i have combined two Liquin mediums on one painting. 

I used Liquin original for first layers and then used Liquin Fine Detail for finishing layer. I have contacted W&N about this and they have told me that is totally ok to combine those two mediums, i just have to keep in mind "fat over lean" rule when i am combining them? What are your thought about this? 

3. In museums there are some paintings that stood the test of time, and these artists did scumbling techniques, and glazes, and it really seems that they sometimes didnt care that much about "fat over lean" rule, and still it looks great. Do you think that we should maybe try to some extent to apply these rules, but not to be very precise and that concerned about it?  

4. And i wanted to ask what types of oil mediums were least changed through time, and prooved to conservators/restorators as most stable? 

I have heard that these were the ones which were more basic (stand oil + turpentine, or white spirit, or something like that). 

What are your  advices about medium choice and what is the best way to  paint in layers? 

Thank you for time and efforts!

All the best!

Marko Karadjinovic 

Gilding 19th century in Portugal

Question asked 2018-10-29 10:05:58 ... Most recent comment 2018-10-29 09:38:00

​I'm reading a 19th century Portuguese treatise on gilding. The master gilder that wrote it was called Francisco Liberato Telles de Castro da Silva. He was in charge of the restoration of the gilded woodcarvings of the church of Madredeus, in Lisbon.

He advocates a recipe for the red bole that puzzles me:

1kg Armenian red bole + between 120-150g of graphite powder + between 120-130g of sanguine hematite. This mix should be ground in pure water (and allowed to dry afterwards? The original text isn't clear on this), then mixed with a spoonful of olive oil and ground again. Just before use, this mix should be ground with a weak solution of rabbit skin glue and another spoonful of olive oil.

I have two questions:

If the original mix is allowed to dry before adding the olive oil (as the text strongly suggests) then a spoonful wouldn't be enough to wet the bole - so perhaps he didn't mean to fully dry but just to allow some of the water to evaporate, so the oil could be added to the thickened paste.

Could this very small amount of olive oil be there just as a plasticizer? Wouldn't the fact that olive oil is non-siccative create problems with the drying of the mordant and also with the burnishing? On the other hand, I know that the most beautiful burnishing is achieved when the bole is just before fully dry (a few hours after, not a few weeks after)... maybe the small amount of olive oil replaces that necessary small amount of humidity, allowing top level burnishing to be done after all the water in the bole evaporated?

Many thanks!


Acrylic Varnish info

Question asked 2018-10-24 09:18:36 ... Most recent comment 2018-10-24 11:18:36
Varnishes Acrylic

​Hello! I am new at the forum, i am very glad to be here. I am painting mostly with oils, egg tempera, but i also do paintings with acrylic.  I have a question about varnishing acrylic painting. Recently i bought Royal Talens Amsterdam Acrylic Satin Varnish and tested on one piece, and it looks really good. This is removable varnish, based on white spirit. I contacted Royal Talens also, and they told me that i dont need isolation coat because this is removable varnish based on white spirit, and it can be removed with the same solvent. My question is what do you think about these types of varnishes, and do you think it is a good practice to varnish acrylic paintings with them? The composition of this varnish is : Acrylic resin, white spirit, turpentine oil, matting agent (silica). Thank you

Varnishing the Edges

Question asked 2018-10-19 22:27:58 ... Most recent comment 2018-10-23 10:52:51
Varnishes Oil Paint


I was wondering if the edges of a painting should be varnished as well, or just the front of it? I paint the edges too so I figure I should varnish it but I wanted to seek professional opinions here. 

Adhesive properties of sun thickened oil

Question asked 2018-10-18 17:09:14 ... Most recent comment 2018-10-22 17:37:04
Oil Paint Paint Mediums Drying Oils

​Ralph Mayer speculates that, because sun thickened oil is partly oxidised, it's adhesive proberties may be compromised to some extent.
Do you know if this has been tested at all?

Egg Tempera Glazing Medium

Question asked 2018-10-14 09:15:37 ... Most recent comment 2018-10-19 14:55:07
Egg Tempera

I have a painter friend who wants to isolate every layer of tempera she applies because she vigorously works each new layer yet doesn't want to affect underlying ones.  She wants to work in a similar vein to the English painter Nina Murdoch, whose working method is described as egg tempera alternating with varnish layers.  My friend wrote Murdoch to ask what she uses as a varnish but did not get a reply. I've read catalogs that describe Murdoch's work -

One image shows a very high gloss, saturated surface – so I am puzzled what Murdoch could be using to achieve her working method and high gloss, but which keeps her work in the realm of "Egg Tempera".  (Of course I realize that artists' descriptions of their work, catalog captions, even museum labels are not always complete or completely accurate). 

The catalog also mentions Murdoch's favored glazing medium recently went out of production; coincidentally my friend noted Sennelier's egg tempera glazing medium has been discontinued – could that be Murdoch's secret formula?  We don't know. I couldn't find Sennelier's glazing medium ingredients but their binding medium is made from egg, oil and gum Arabic.  I would rather such a medium not be described as "Egg Tempera"; I think it would be more clarifying to call it Tempera Grassa or egg/oil emulsion - but I realize I have no say in the matter. :-)

I've wondered how the tubed egg temperas (which are in fact tempera grassas) by Zecchi, Sennelier, Rowney, etc are made - they can't use a yolk in its entirety as the paint would putrefy.  Do you know how they do it?

Back to Murdoch's work, and my friend who's trying to understand it; she also prefers the more saturated, rich look of varnished tempera.   I have told her that, while alternating multiple layers of ET and some sort of water insoluble isolator is potentially quite problematic, I believe there are reasonably durable ways to isolate a final tempera layer and then varnish it.   


Any thoughts on the above are welcome.

Koo Schadler 

prints and oils

Question asked 2018-10-18 08:46:32 ... Most recent comment 2018-10-18 14:34:44
Oil Paint


I got this question from a student of mine. He wants to paint with oils on top of a inkjet print. My concern is that those inks might bleed into the oilpaint. Does anyone have experience with this?

Alkyd and Glitter

Question asked 2018-10-09 00:44:21 ... Most recent comment 2018-10-18 11:08:46
Oil Paint Alkyd Industrial and Non-Traditional Products

​I want to try adding glitter to some paintings of mine, but I'm wondering how I can do it properly with oil paint?

I found that using Galkyd Lite by Gambin produces the least yellow tinted colour shift, and holds the glitter in perfectly so none flakes off. However I don't know if this could later be an issue due to either the alkyd yellowing (will it yellow?), or the fact that a layer of alkyd is sitting on top of a layer of oil paint. 

What issues could I face here, and are there any tests I could conduct to see if it will last? I plan to sell the work so I want it to be high quality. 

egon schiele

Question asked 2018-10-10 06:29:40 ... Most recent comment 2018-10-17 14:26:25
Animal Glue Art Conservation Topics Gouache Sizes and Adhesives Scientific Analysis Technical Art History Watercolor

​hi there, egon schiele used watercolour and gouache on different similie japanese papers / fake vellums & brown wrapping paper. did he size this wrapping paper to hold the paint or was the paper made in 1910 heavily sized to avoid seepage? either way is there a paper out there today that is similar to the paper he used? it is hard to find tinted papers for this medium. i have tried sizing my own papers with rabbit skin glue & gelatine, using coloured washses, kraft legion stonehenge paper and strathmore tan for mixed media (none have the same affect as schiele - his colours stand on the paper - not absorbent). apparently he use strathmore japan paper produced by mohawk fine papers. i have contacted both companies and both have directed me here. i have also contacted dr. jane kallir, the world's leading egon schiele scholar. i have also tried wetcanvas. does anyone know if his works have been under conservation. can anyone help? thanks

Saponified Wax?

Question asked 2018-09-27 15:20:04 ... Most recent comment 2018-10-17 13:47:58

I am working on reconstructing a Fayum mummy portrait, and a few sources I've read have mentioned methods that might have been used to make the wax easier to paint with. There's a small section in "Ancient Egyptian Materials and Technology" about "punic wax" that suggests beeswax was possibly saponified to make it water soluble. Do you know if that theory is plausible or have you tried painting with punic wax?

Priming Wood/Canvas Panels

Question asked 2018-10-16 12:41:07 ... Most recent comment 2018-10-16 19:59:38
Oil Paint Rigid Supports Flexible Supports Art Conservation Topics

​I was wondering if there's any benfit to using a layer of alkyd resin like Galkyd to help seal a painting? Will it help reduce moisture absorbtion? 

I would apply it as the last step before painting, so my process would be: size wood panel using gac 100 x2 layers, adhere fabric to the panel with beva film, size fabric using gac 100 x 2, gesso or oil ground layer x2, and then 1 layer Galkyd and Gamsol 1:1 ratio to cover that.  I would be coating the entire panel front and back, including edges. 

Is this overkill or is this a good way to do it? I just want to get a smooth and as warp resistant panel as possible. I'm using the cotton canvas overlay so that if the panel is ever damage the painting can be taken off, instead of having it painted right onto the wood.  

Isolating Egg Tempera

Question asked 2018-10-13 16:00:03 ... Most recent comment 2018-10-16 07:53:35
Egg Tempera

Several years ago, when testing isolators for egg tempera, someone (a materials expert) recommended Golden's GAC 500 and Acrylic Gel Medium as isolators.  Being water-based, I was skeptical they could be applied without disturbing a relatively new egg tempera painting, but in fact they went on fine and worked well.  I haven't used them since but suggest them to students as possible isolators (preferably with more testing). 

Recently another materials expert told me that using GAC 500 as an isolator could prove problematic as it would create a completely unbreathable layer that would stop the egg tempera from properly oxidizing/curing, and could cause potential bloom or mold problems.  Your thoughts?



Pastel substrate-Dibond, Alumalite

Question asked 2018-10-11 13:53:09 ... Most recent comment 2018-10-12 21:35:50
Rigid Supports

Good afternoon,

I am a pastel artist who is searching for a lightweight aluminum substrate to mount pastel paper that can be used in the studio or in the plein air environment. The papers that I am considering to bind to the substrate is Sennelier LaCarte (This surface is created with finely ground (pH neutral) natural cork applied to a 170 lb. (pH neutral) board similar to cardstock) as well as UART paper product (sandpaper material mounted on 4ply or 8ply Conservation Board).

There seems to be many aluminum products available yet looking at your document "Rigid Supports" I have a few questions regarding your selections. The doc states to use a product that has a plastic core yet most are available from 2-5 mm in thickness. A product by the trade name Alumalite has a fluted plastic core and available in 3/8" and 1/4" thickness. Since I paint out of doors the thicker gauge material seems optimal to avoid bending corners and edges of the surface in the outdoor environment. Is the fluted core acceptable? What is the minimum thickness appropriate to avoid warping? A local distributor stated that Dibond and Alumalite are pre-painted with a white aluminum finish yet your document states to avoid anything that does not have a polyester coil coating. The coating that you are referring to is it a high quality pre-painted finish onto the metal prior to fabrication-heat cured/cooled and rewound for shipment? If both substrates are acceptable do you recommend cleaning the panel with 99% isopropyl alcohol prior to applying an adhesive or what cleaning product is preferred? Also what adhesive(s) are considered appropriate to bond the aforementioned pastel surfaces to the aluminum substrate (BEVA 371 adhesive film/other)?

Thank you,


Tackifier / plasticiser for carnauba wax based encaustic medium

Question asked 2018-07-25 19:53:57 ... Most recent comment 2018-10-11 21:34:43
Paint Making Paint Mediums Encaustic

​I experimented with 100% carnauba wax and pigment on a hide glue gesso ground. As you probably know it was hard and glossy, but brittle, and it was easy to chip off. I am reluctant to add dammar because it may yellow. I considered Canada balsam, but after looking into it seemed that it might have the same problems as dammar. Could a hydrogenated rosin help, or microcrystalline wax? II found an article from the food industry that found polysorbate 60 was an effective plasticiser for carnauba, but I think that would make it susceptible to moisture. I  understand my responsibility to do my own tests, but any suggestions on what I might test? 

Lead Point

Question asked 2018-10-05 17:44:20 ... Most recent comment 2018-10-10 19:08:05
Drawing Materials Health and Safety

​I just received a lead point and lead-tin point from Zecchi's.  How readily is lead transfered to the skin via either the stylus itself or from marks made on paper (i.e. resting a hand on a drawing)?  Any  other lead point consdierations I should keep in mind?


Koo Schadler

Oil paint on Alumacomp surface

Question asked 2018-10-05 14:31:30 ... Most recent comment 2018-10-08 15:17:07
Oil Paint Art Conservation Topics

​Jerry's artarama makes an aluminum metal surface on which they claim you can paint directly onto. My question is can really I use oil paint directly on this surface (without any gesso) and will it last or will it chip off over time?

Collage Adhesive for Oil Painting

Question asked 2018-10-05 00:08:06 ... Most recent comment 2018-10-07 01:58:47

I have an Ampersand Gessobord which has an additional 2 coats of acrylic gesso and a thin layer of oil colour using Liquin. I would like to adhere a small oil painted sheet on Daler-Rowney Oil Painting. Is this possible? What should I use as an adhesive?​

Regalrez 1126 as a final varnish

Question asked 2018-10-05 08:52:09 ... Most recent comment 2018-10-05 21:20:18
Varnishes Oil Paint Art Conservation Topics

​Is there any particular reason why Regalrez 1094 is prefered as a varnish over Regalrez 1126? I gave up on using 1094 as a varnish a number of years back--I just don't like how it handles, or how it's really finnicky and tends to form an uneven sheen (and its high solubility means that you can't really apply multiple coats to even out the sheen), and I don't like how it tends to get tacky when you touch it, or when it gets too warm in my studio. Its glass transition temperature is so low that it can be above Tg at room temperature, on a warm day! That may not be a problem in the carefully-controlled climate of a museum, but for a painting that's going to be hanging in someone's house, and that may need to be shipped in the mail (how hot is it going to be in the back of that UPS truck?), it's a problem. 

So I went back to using dammar, because while its aging properties are inferior to those of Regalrez, it makes an aesthetically pleasing varnish that is easy to use with predictable results, and its Tg is high enough that it's not going to get tacky and turn into a dust magnet just because you don't have the AC turned on. 

But doing some reading on varnishes, apparently Regalrez 1126 is a possible alternative? It has a higher molecular weight and a higher glass transition temperature than Regalrez 109