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Question asked 2018-02-01 08:27:20 ...
Most recent comment 2018-02-06 10:36:50
At the moment I am testing Chroma Color from a Spanish factory called La Pajarita. It seems Artists like Dali have made use of their paint. I am trying to find out if it would be suitable for our Shop in School, of my Art Academy.
The one thing I am concerned about is that it is made with vinyl in stead of acrylic. I was under the impression that acrylics are superior to vinyls. As far as I know the plastcisers in acrylics are internal and often in pva's external, am I right?
According to them, however, when they were considering transition from vinyl to acrylic as a binder, their vinyl tested better then most of the acrylics from their competitors. And that is why they stayed with vinyl.
My knowledge is too limited, here. So I hope you people can help me out.
Answers and Comments
Here are my best guesses: According to their site, the manufacturer offers both craft-grade and fine art-grade paints, and lists the one you mention among the latter, so they are representing it for permanent art. There are PVA products including adhesives and sizings that meet this standard, so personally I don't see any reason to be particularly suspicious of their claim of durability. Any speculation on plasticizers would be a guess without information from the source, and they might be averse to sharing something they regard as a proprietary secret. It's possible another Moderator will know more about what plasticizers are currently used with vinyl-based emulsions/dispersions. (I think it's pretty unlikely that the formula has gone unchanged since it was used by Dalí.)
I fear there is just not enough information to go on. What type of testing did they do? Following what standards? Can they share the results in a quantified manner? All of those things would be important to give their statement about the vinyl paints as doing better some weight and backing. At the same time, i t is good to realize that vinyls encompass a very wide field of chemistries and polymers and making generalities just isn't valuable because it glosses over precisely those fine points that can make all the difference. Just to take one example of the problem with generalizations, prior to the 1960 most vinyls were plasticized externally - meaning a separate plasticizer was added to a single, or homopolymer, binder - and these generally had issues with the plasticizer being volatile , leaving the system over time, and becoming increasingly brittle as a result. Because of that, more modern formulations have generally gone to a copolymer system where the harder vinyl is joined with a softer resin (hence "co-polymer") to allow for a more stable and flexible system without the concern around plasticizers evaporating away. And of course there are many possible combinations of copolymers, complicating all of this further. But, and here is a good illustration of the danger in just these types of generalizations, a PhD thesis I link to below concluded that the homopolymer formulations in the paints they were studying appeared more stable than the copolymer ones. So.....what can I say....its complicated.
If interested in pursuing this further you might want to take a look at the following papers, PhD thesis, and book:
Modern Paints Uncovered
Unfortunately none of these will provide a definitive answer to your question. The book Modern Paints Uncovered is good to the extent that it covers several case studies involving artwork done with vinyl paints, and so gives some examples of the types of analysis and concerns conservators are involved in.
In the end, as in so much around art materials, it comes down to the trust in the company, the testing they have done, and how much they are willing to share. Also, keep in mind, the vast majority of research around the durability of vinyls has happened in the context of commercial housepaints, where the vulnerability of vinyls in exterior applications and UV exposure are well documented. Which is also why nearly every exterior housepaint you will find are formulated with 100% acrylic, while interior paints will use the less expensive vinyls. But these types of concerns might be moot for a work meant indoors.
As usual, your post is filled with dispassionate facts.
agree that there is just not enough info to draw any real conclusions about the
performance of these paints. PVA solutions are rather simple and the Tg is a
result of polymer chain length. Emulsions and dispersions of PVA can run the gamut
depending on a huge variety of factors and the influence of other ingredients.
Some PVAs may exhibit cold flow at room temp and others will not. As an
illustration, has anyone ever seen cold flow in dried white glue like Elmer’s
(a dispersion of PVA and many other proprietary ingredients)? I have not.
We do know that acrylic dispersion paints are often superior to
PVA dispersion paints but there is no way to say that a particular paint is
better or worse without far more info about ingredients and formulations.
It does seem fine to mix this paint with acrylic dispersion
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