MITRA Forum Question Details

​Hi - 

Jumping in a touch late but wanted to offer our own thoughts on the issue. We think you will find many statements about commercial products vague and generalized, in large part, because it is such a vast area and with such a wide range of quality, that making hard and fast statements would be unfair and largely gloss over the differences you can find. So in most cases it is best to deal with the issues on a case by case basis. So, for example, we are just now getting a series of really good conservation studies looking at the deterioration​​​ and problems of paintings done in the 50s through 70s, when use of many commercial coatings were common, and as you read through these you come away with a very strong sense of caution. The painters then, like many today, reached for commercial products to save money and for convenience, but now many of those works are in horrible conditions as a result. And that 50-60 year time lag for many of these things to show up fe​els about right - it takes time for embrittlement​, for example, to develop and cause issues.​ A great case in point are many paintings by Richard Diebenkorn, which you can read about here:

Ann Alba's A Question of Technique: Condition Issues Associated with Layering Structure in Richard Diebenkorn’s Ocean Park Series​  (starts on page 88)

AIC’s 40th Annual Meeting – Paintings Session, May 9, “Relating Artist Technique and Materials to Condition in Richard Diebenkorn’s ‘Ocean Park’ Series”  by Ana Alba

One of the things that is interesting is that the most problematic paintings all come from a middle period when Diebenkorn had turned from using artists' acrylic gesso to using various commercial materials as alternative primings, and that when he returned to acrylic gesso the cracking that is seen also subsided. 

And here is another example from the literature worth looking at:

Problems associated with the use of gloss house-hold paints by 20th century artists​'

​​The point in all this is that these cautionary tales, such as they are, are definitely abundant but are unfortunately scattered throughout the conservation literature in singular papers and studies on specific treatments or paintings. So sometimes not easy to point to. But for those of us following the literature over these many years, enough has come out for those vague general warnings to feel informed and meaningful and not given simply to scare or force you into expensive but unneeded materials.
Speaking generally, we can share some things that might help. Acrylic resins are a HUGE category and at this date we have examined and tested well north of a 1000 binders, and the fast majority of those have failed in testing to be suitable, we feel, for durable works of art. At the same time, most of what we are testing are the same resins industry draws from but their selection criteria are very different and their testing regimes as well. So, for example, in house paint a relatively hard resin is often desirable because that means it will resist dirt and grime, although of course at a cost of flexibility - but then, walls are so rarely rolled up! They might also choose a resin that chalks for an exterior application as then the coatings have a form of self-cleaning mechanism. And we have sent a lot of very cheap preprimed canvasses and canvas boards through artificial UV aging and have been shocked at how yellow they often come out. So that is another factor that often a house paint will not need to factor in.

That said, we also know that there are times when commercial paints need to be used - for example, many murals are simply not economically able to be done using artists paints. In those cases we will often work with the artist to try an recommend least-harm strategies - such as adding in artist quality acrylic mediums into the paints to increase flexibility. But these are always done with the knowledge that they are compromises at best and not equivalent in quality.

I leave you with the sobering thought that many acrylic gessoes are  themselves of poor quality and we would strongly encourage anyone to stick with the better brands. Or as I like to counsel - work with brands that have a reputation at stake, who would be fearful of ever being associated with failures in the materials they make.

I hope some of the above is helpful. there is more I can share but let me do that in a different post and get this up for now.

Best regards,

Sarah Sands
Senior Technical Specialist
Golden Artist Colors​

Let me continue from my previous answer and try to address the issue about testing.

One thing to look at is simply adhesion of whatever paint you plan to apply on top. You mention working in oils, so the following link will not be as relevant, but we have actually had an ongoing issue of artists seeing adhesion failures on top of inexpensive preprimed supports, to the point that we wrote an article on the topic and shared some very simple testing protocols artists could use to see if their canvas might pose an issue (essentially just putting a drop of water on the surface and observing the contact angle):​

Pre-primed Canvas Adhesion Testing Procedures​​

Clearly the failures speak to some form of contamination or incompatible material, and while we have not tested oils for the same issues, I would be concerned about using any canvas that could not pass this test as it sends up a red flag.

It appears that you know about the crosshatch adhesion test, but if not you can find that covered in the following piece under Adhesion testing:

Testing for Your Application​

We would recommend testing a few colors of different types, and to test after they are thoroughly dry and can pass the thumbnail test.

You should definitely test for oil strikethrough. A couple of ways to do this. One, which is quite a hard test, is to apply three drops of linseed oil to the canvas and let it sit. It should not form an oil spot on the opposite side and, equally important, should not dry to a hard bead sitting purely on top. It should slightly soak in - showing good wetting out and mechanical adhesion - but not so much as to be drawn through to the other side. Alternively, apply a generous layer of a slow drying oil paint to see if the oil penetrates through.

Another test is a simple fold test for flexibility, where you should be able to fold a sample of the primed canvas completely back onto itself 10 times without showing any signs of cracking.

Moving on from there, test for yellowing. this is a little harder for you then us, as we have accelerated UV exposure equipment, but you can certainly try to at least tape up a sample (while keeping another in dark storage) to a south facing window and check after 3 and 6 months, then again after say 1 and 2 years. It should remain white.

You can test the pH of the surface with a simple pH test pen​ (Google it) and you should get a neutral or alkaline reading. 

Test under a UV black light for fluorescing - it should definitely NOT fluoresce, and any glow would indicate optical brighteners, which degrade.

Other types of tests would require a dedicated oven to expose sample to 140F for extended periods, which can give you a read on accelerated aging of the binder, and is something we do. Also if tehre are plasticizers in the coating - as many inexpensive vinyl ones will have - those will tend to evaporate away with heat and so embrittlement can often be seen with prolonged heat exposure.

There are other tests but let me stop there. As you can see there are a lot of aspects to look at, and some would be impractical for you to really test -  such as flexibility at different temperatures and humidity levels.

Finally, let me leave you with one story about someone who used a very high quality commercial paint for many years as a ground for their paintings without having any problems. All of a sudden, however, our High Flow paints were beading up and would not adhere. They called us to see if we could figure things out. We went so far as to purchase the primer to try and reproduce the issue - and sure enough, we could. Looking into it, what we discovered was that the paint was now 'new and improved' and touting cutting edge stain resistance and easy wiping off of grime and dirt. All sounds great in a housepaint! However, to achieve this they were adding things into the paint to make it very hydrophobic once dry, thus the reason our paints would not adhere. Its a great case where even a high quality commercial product often is aiming for different properties and qualities then you need or want in an artists' material.

So, we now its a pain and not the cheapest solution, but we would actually counsel you to do whatever you can to afford and use the best quality artist grounds as you can as really the entire life of the painting is riding on it. Literally.

Sarah Sands

Senior Technical Specialist
​Golden Artist​ Colors

Great to get your response and glad you had a chance to read the articles. As to your sense of my wording being 'curious', let me share a few thoughts that may help explain my perspective. One thing to realize is that the first link goes to a presentation from 2010 that looked specifically at 4 paintings done within a very tight timeframe when his approach to canvas preparation was changing and it is true that you get a bit of overlap and combination of approaches. But the middle period I was thinking of came from the much longer stretch of time covered in the second article, which is mostly a summation of a paper Ana presented at the 2012 AIC Conference. That was a presentation I happened to be at and remember the impression it made on me, but unfortunately there is no complete, publicly available copy of that paper I can link to. That said, let me quote from the summary:

"He painted consistently on unsized cotton duck but his choice of preparatory materials fluctuated over time. Between 1968 and 1973 he used white acrylic gesso and toned it with diluted acrylic.  In some cases he added alkyd.  From 1973 to 1978 he transitioned from white to clear preparatory layers, presumably in order to maintain the raw canvas color and achieve transparencies in his paint layers.  Scientific analysis suggested the clear material was synthetic and consistent with Rhoplex AC-33. This was more or less confirmed by photographic evidence of showing large jugs labeled as Rhoplex located in the artist’s studio.  By 1979 Diebenkorn had returned to using acrylic gesso almost exclusively.​"​

There is also this Abstract from the Preprints for that year’s AIC Conference as well: http://www.conservation-us.org/docs/default-source/periodicals/psg-postprints-2012-vol25.pdf  (page 29)

"The analytical work revealed changes in the artist’s materials during the time span of the series. For example, analysis of paintings from 1974 to1979 suggests that Diebenkorn started incorporating clear synthetic preparatory layers in addition to pigmented gessos. This clear layer was confirmed to be Rhoplex AC-33, which was readily available during the time in which the paintings were executed. Cross- sectional and microscopic examination of the paintings also indicated that Diebenkorn prepared a few of his own grounds by mixing clear acrylics with white pigments. Furthermore, by 1979 through the end of the series, analysis suggests that he favored pigmented commercial acrylic gessos almost exclusively. 

Condition issues in this series were also documented, and a database was created to chronologically track material changes in the paintings and visible areas of instability. Correlations between his choice of painting materials and the general condition of the paintings were noted. In general, paintings that contain layers of brittle alkyd and oil paints over clear synthetic preparatory layers exhibit more severe cracking than those that do not exhibit this layering structure. This observation is illustrated in the database. Pre-1974 paintings tend to be in better condition than some of the mid-series paintings, where unconventional layering structure is observed. Also, when the artist started using commercial pigmented acrylic grounds around 1979, the number of paintings affected by surface cracks diminishes. Painted areas that consist of multiple layers also generally fare worse than areas without heavy layering and reworking."

So there really was a period when acrylic gesso was essentially phased out and Rhoplex AC-33 took over as the primary sizing material, and that overall the works from this middle period are the ones in much worse shape.​​ Some of the confusion about my wording might be caused by the fact that the works in the 2010 study are from a tight cross section of time during that latter transitional period (1977-79)​ where he is moving from the use of Rhoplex back to just acrylic gesso. So it would not be surprising, I think, to find acrylic gesso being applied directly on top of the Rhoplex in Ocean Park 111 (1978), while the two paintings mentioned as being in good shape (115 & 125 from 1979-80) were commercially primed with acrylic gesso alone and had no Rhoplex at all. 

Anyway, I ultimately agree with your point, in terms of the main culprit, namely the thick layer of AC-33 with its softness and mobility combined with the brittleness of the commercial alkyds. And really my overarching point is simply that commercial products can bring with them unintended  issues, and that Diebenkorn's use not only of the unadulterated industrial resin AC-33, but also of alkyd housepaints, led to real problems that he clearly did not anticipate.

I agree that by painting on rigid supports folding and flexibility testing is likely not needed - although even wood supports do expand and contract. And yes, aim for commercial materials of the highest quality if you decide to go there, with price often being a good guide, although keep in mind the story I related in the second post where an artist was using one of the absolute best quality housepaints as a ground, but some of that percieved 'higher quality' for the company and their regular customer was the touted stain and dirt resistance, which led to the adhesion problems. Just realize that commercial paint companies are aiming for a different market with different expectations of service life and longevity, and that even a basic acrylic paint is a balancing act of some 15 ingredients and chemicals that can all cause their own issues. 

One last thought - if going commercial for a primer, have you thought about Zinsser's B-I-N, a pigmented white shellac? I ask not because I think it escapes all the issues and problems, but it has the distinct advantage of being a much more simple and basic paint with fewer moving parts and unknowns.​

Sands, Sarah​