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  • Concern re driers causing possible darkening in oil paints made with semi drying oils? ApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2017-08-21 04:03:00 ... Most recent comment 2017-09-05 10:16:48
    Oil Paint
    Question

    ​Dear MiTRA person

    I recently purchased some oil paints by a reputable German manufacturer who sadly is not explicit about the oils used as binder. They admit to using a combination of oils but the feeling on online forums is that there is probably a preponderance of safflower or perhaps even sunflower oil. I have some concerns about using them because inevitably they must have added some driers and I am given to understand that some metallic driers like manganese can cause darkening in the paint film over time.  As is noted here in the resources articles, most paint manufacturers do add driers to one degree or another but the devil is of course in the detail ie how much? I've emailed them to enquire as to whether they have done any testing or have any reassuring information on this front but the response was a bit confusing as they kept directing me to information regarding the lightfastness of these paints. (And by the way they use the Blue Wool scale to assess lightfastness which as far as I know is very outdated!). Do I need to be concerned regarding darkening when using paints of this type? 

Answers and Comments
  • EditDeleteModerator Answer

    Having very little information on which to base an answer, I would guess that a "combination" of oils means a more neutral-colored vehicle was selected for whites. If these are professional-grade, manufactured oil colors, I would assume driers are added in very precise, laboratory-tested proportions calculated by paint chemists. At least, that's my experience with paint manufacture. Exact formulas for oil paints are often held as proprietary secrets, though it strikes me as unusual not to disclose at least generally which oils make up the vehicle.

    Many manufacturers (Utrecht included) select oils other than linseed for pale colors and whites. The use of neutral-colored oils for whites is not experimental or exclusively modern- the practice dates back centuries in the Northern tradition and is mentioned in manuscripts including William Beurs' treatise. While arguably not the equal of linseed oil, safflower, poppy and walnut oil (all similar in ratio of linolenic to linoleic acids) are still considered proven paint vehicles suitable for permanent painting. Sunflower oil is available with different fatty acid ratios, so I wouldn't make any assumptions as to general suitability based on food-grade oils- if sunflower is being used, it may be a type that is better for painting than for eating.

    Matthew Kinsey, Utrecht Art Supplies
    2017-08-21 13:18:21
  • ApproveRejectUn-ApproveUser Comment

    ​Thanks Matthew   It's not just in the whites though; it's the entire paint line. Their description of the vehicle is as follows "Combinations of pure, high quality plant oils produce good adhesion, optimum absorption of the pigment and less tendency to yellow". I have a very sensitive nose and cannot smell linseed oil in these paints. They are virtually odourless--like other paints I have that are made with safflower oil. My guess would be safflower oil is the main vehicle but who knows? They are a professional paint line; in fact they use the word Professional in the paint name. By the way, what do you think of their use of the Blue Wool Scale? Can I trust the lightfastness ratings of these paints provided by the manufacturer? 

    2017-08-21 18:33:13
  • ApproveRejectUn-ApproveUser Comment

    ​​Presumably, you are talking about Schmincke Mussini. I've had some correspondence with them in the past; they don't disclose their recipes for specific colors, but across the range they do use linseed, safflower, sunflower, and poppy, with linseed being the primary oil that is present in some amount in most colors (with the exception of the whites). They almost certainly use driers; their titanium white dries in about four days in thin layers, and titanium bound in safflower or poppy oil simply does not dry that quickly without some help. 

    As Matthew says, driers added in precise amounts during paint manufacture generally aren't something to worry about (unless you want your paint to stay open longer). I've been using Mussini paint for about fifteen years, and have never encountered any issues with darkening. Their titanium white (which as I mentioned, almost certainly contains driers) is tied for first place as "brightest, least yellowing white" on my eight-year old white test sheet. (Blockx titanium white in poppy oil is the other one, but the Blockx white takes twice as long to dry in thin layers, and can remain wet for more than a month in impastos.)



    2017-08-22 16:36:25
  • ApproveRejectUn-ApproveUser Comment

    ​Thanks but no, actually, I'm not talking about Schmincke Mussini. As far as I know they (Schmincke) are fairly open about the vehicle used in that particular paint, which has been around for a very long time and gets excellent reviews on artists' forums. The paint I am in fact talking about was formulated more recently by Schmincke. It is called "Norma Professional". Norma Professional does not have a considerable degree of linseed oil. I suspect it contains no or very little linseed oil. I find it strange that they are open about the vehicle used in one paint and opaque about that used in the Norma range. 

    2017-08-22 17:43:16
  • EditDeleteModerator Answer

    The Blue Wool Standard lightfastness test is a good method for the artist to conduct in-studio testing of colors. It's not up to the ASTM D 4303 standards, which are more rigorous.

    Personally, I don't see any reason why a paint maker would not disclose what specific oils are used in a given color, barring some tiny amount of a proprietary ingredient. Nevertheless, where listing of the exact vehicle is concerned, as I understand it, under ASTM D 4302, where multiple oils, resins or gums are used in multiple colors across a paint line, it is permissible to include all possible on a given label (e.g. "Alkali Refined Linseed or Expeller Pressed Safflower Oil"). Compliance with ASTM D 4302 is voluntary, however. 

    It's important to note, BTW, that ASTM D 4302 actually prescribes the minimal use of driers for slow-drying colors that would not otherwise meet the standard for acceptable drying rate.


    Matthew Kinsey, Utrecht Art Supplies
    2017-08-22 17:47:15
  • ApproveRejectUn-ApproveUser Comment

    ​Further to my previous comment just posted (I see I can't edit) I jwanted to add that i am relieved to hear that, in general, I don't need to be overly concerned about the use of driers in oils made by reputable companies--so thanks for that. I do like the Schmincke Norma paint and their pigment choice is what I would hope for in a professional paint line but I am still puzzled as to why Schmincke would be using the blue wool scale for lightfastness and I'm wondering whether such ratings are sound? 

    2017-08-22 17:51:16
  • ApproveRejectUn-ApproveUser Comment

    ​I see we cross posted so please ignore my last query. 

    2017-08-22 17:52:08
  • EditDeleteModerator Answer

    I cannot speak to the exact oil mixtures in the Norma paints. I hope that in near future that we can have a technical contact at Schmenke to help answer questions like this.

    The paint industry does not, in general, give exact formulations, but a list of the major ingredients. This can include precise materials like (eg walnut oil) or less precise (eg mixtures of selected drying oils) while most will give the exact pigments included in their paint. They almost never give exact amounts of small additions of stabilizers, driers, etc. Modern fine art paint manufacturers likely add different amounts of driers to each pigment oil mixture (especially in their professional lines) to moderate and help to equal out the drying across the entire range, not just a single percentage for all paint.

    As far as drying oils, please refer to our section on this subject in our resources section. The only one that you mention that concerns me is sunflower oil. Yes, Sunflower oil is available with different fatty acid ratios. However, there have been some examples where professional oil paints were made with large amounts of sunflower oil and these have exhibited major long-term drying defects. Yes, these were probably made with an improper grade of sunflower oil but I can see no advantage in its use at all other than its extreme economy.

    Brian Baade
    2017-08-22 19:45:52
  • ApproveRejectUn-ApproveUser Comment

    Thanks Brian. This is very useful. I would never expect a manufacturer to give me exact ratios etc but I think identifying the oils used is only reasonable--as well as some assurance that some thought has been given to the possibility of driers (or oils themselves) causing potential long term problems-- and that steps have been taken to minimise these potential problems to a reasonable degree. Instead, what I got from the Schmincke technical expert I emailed was repetitive directions to read the product literature regarding lightfastness--talk about confusing the issue !  Perhaps there was a language problem. In regard to your last statement did you mean long term "drying" defects or "dry" defects ( in relation to safflower oil as a vehicle)?. 

    2017-08-22 22:36:51
  • EditDeleteModerator Answer

    Brian, according to my experience, you're correct- each color in an assortment is individually formulated, and siccatives are applied according to the characteristics of the pigments used.

    Matthew Kinsey, Utrecht Art Supplies
    2017-08-22 23:07:50
  • EditDeleteModerator Answer

    Sorry, I intended on wrting drying.

    The problematic paints were formulated with sunflower oil. You may want to write the manufacturer and ask about this.

    I am sure that some, or even a lot, of testing is performed before the products are brought to market.

    My opinion, however, is that even greater transparency about ingredients and materials would only make everything better and give those customers that care more info to guide their buying decisions. Additionally, it could help differentiate lower and higher quality of Artist's or Professional grade paints. The terms today appear to be rather nebulously used beyond pigment choice.

    Brian Baade
    2017-08-23 11:43:39
  • EditDeleteModerator Answer

    I agree, there's really no good reason to be vague about the general composition of an oil paint vehicle. If artists are curious enough about your products to ask for detailed information, it means they are very interested in using them. Having specialist craftsmen talking about your products is an advantage you can't buy or conjure up, and when it happens, it's a good idea to make yourself available! 

    Matthew Kinsey, Utrecht Art Supplies
    2017-08-23 17:33:28
  • ApproveRejectUn-ApproveUser Comment

    ​Thanks again, Matthew and Brian. I've emailed my Schmincke contact again requesting further information but I suspect I will once again be redirected to the company spiel on lightfastness. If so, I may ask a German friend to compose a further email, just in case the problem is one of interpretation due to language difficulties. 

    2017-08-23 18:41:29
  • ApproveRejectUn-ApproveUser Comment

    ​in case anyone is interested, I've received information as to the oils used in the Schmincke Norma Professional Oil paints. They are linseed, safflower and sunflower oils. I was told this by the tech person at Schmincke who I've been emailing. He informed me that the darker colours contain relatively more linseed oil and the lighter colours relatively less. Personally I can't smell a lot of linseed oil in my 2 darker colours--indanthrene blue and a dark alizarin substitute colour. He also assured me that if used thinly, in a classical painting style, there won't be any "drying defects" . Furthermore he insists that any potential darkening or other colour changes caused by any component of the paint would show up in their lightfastness tests, and so far none have. My new concern is efflorescence but I'll start another post for that. 

    2017-09-05 10:16:48
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