So, to varnish an acrylic painting with temporary varnish I would need a coat of something else first, so that later on I would be able to safely remove/clean the varnish. Which exact material is this coating/brand? Thank you.
Vielsa,

But what he does in the oiling out video is good practise. You can also use linseedoil for that. That gives a lovely satin shine, and doesn’t darken or yellow if you don’t use too much.

JP

Thanks Larry for your response. Regarding using dammar in artist mediums and varnishes, yes this could be problematic, especially as the medium is probably used partly because of its good glazing properties, meaning it will be in thin films directly below the varnish layer. Also, dammar is VERY brittle. For a single, thin coat of dammar varnish, this brittleness is not too bad, but something like alla prima painting with dammar in the medium is inherent vice.

For those painters who don’t mind getting a little into chemistry, there are some interesting small conservation articles on varnishes here at Conservation Online:

http://cool.conservation-us.org/waac/wn/wn17/wn17-1/wn17-107.html

These conservators make a big emphasis not just on natural vs. synthetic varnishes but also whether the varnish has a high or low molecular weight. Higher molecular weight varnishes are *usually* synthetic and have a lower refractive index, making them more matte. Varnishes like dammar have a low molecular index (and a higher refractive index > glossy). The problem is that high molecular weight varnishes can crosslink with paint films and can become increasingly insoluble. The worst of these are methacrylates (aka acrylic varnishes) which display reduced solubility after ten years. PVA, polyvinyl acetate, another matte varnish, does not appear to have this problem and may be a better synthetic alternative. Incidentally, PVA is often used for sizing paintings (a synthetic substitute to rabbit skin glue). Also, conservators note that high molecular weight varnishes are trickier (thicker and quicker to dry) to coat and tend to attract more dust, but that may be the price to pay if you want to avoid a glossy surface.

There is also discussion on UV filtering agents, especially a class of chemicals called Tinuvin. It seems that very small additions of these agents into the dissolved varnish can exponentially expand the life of the varnish, protecting the painting from fading, the varnish from yellowing and potentially from becoming more brittle (though, like all varnishes, it will do little to prevent oxidation). The exact form of tinuvin, percentage of tinuvin to varnish resin, type of varnish resin used and thickness of the varnish coat (by the nanometer) all have complex interactions, only improving the varnish when the formula is *just* right.

The more I read about synthetic varnishes the more I think they are likely superior to natural varnishes when done right. The problem is “right” could be a very specific chemical formulation and application method that requires significant research and testing. For someone who wants a low-tech varnish that is more forgiving, I still think dammar is a decent choice. As long as you wait a year and a apply a single coat with a big, soft brush while the painting is flat on the floor in a clean room you (or someone else whom you trust, should you no longer have possession of the painting) can’t really mess it up. Leave the synthetic varnishes to conservators and truly scientific painters (Old Master alchemy isn’t very helpful here).

I’m curious if anyone here is using Golden Paints varnishes or GAC Acrylic Specialty Polymers as a varnish. If I was to quit dammar for synthetics, I’d probably start my search there. I would also note that Golden’s website have very thorough technical notes on these products as well a section of research articles that have recently been focused on the issues of using acrylic chemicals (sizings, primers, varnishes) in conjunction with oils and traditional oil painting methods.

Thank you Brian Kelley for your informative and interesting comment. I find it curious that there seems to be such a difference in opinion by the many experts. I’ve often read where modern synthetic varnishes are supposed to be preferred as they are much easier to remove with little or no risk to the underlying painting – now I hear this may be all wrong! I have also read that dammar varnish could possibly bind with the glaze medium or medium with dammar in it and risk removing the paint layer along with the varnish when it’s removed. I am curious to read about good modern alternatives to the slick, salon-style varnishes. I should think the more matte varnishes which use wax might be a good way to go but I’d like to research even more. Here is a link to some general information about this symposium. When I get a chance I’ll look into seeing if I can get the complete text (a publication is available).

One issue that the conservators discuss is that not all varnishes stay soluble indefinitely, which is a problem because even the best varnished paintings will likely need a cleaning/revarnishing every 50-100 years. Many of the modern, petroleum-based varnishes seem to become difficult if not impossible to remove with solvents after several decades. Dammar varnish, interestingly, has a reputation of staying soluble to turpentine for centuries, which is a good thing as dammar yellows more easily than most modern varnishes. Quite a few Rembrandt paintings that had nearly been lost under dirty dammar varnish for centuries are now cleaned, revarnished and looking brand new.

Another issue was that it may actually be more critical for acrylic paintings to be varnished than oil paintings. The microscopic surface of acrylic films have similarities with that of a sponge, which makes it very easy for dirt and grime to attach. Oil films are much smoother as well as harder and more resistant to scratching than acrylic. Ironically, because acrylic is inherently more “modern,” it seems fewer acrylic painters varnish than oil painters.

Also, conservators really get anxious about cleaning the varnish off a painting that has passages of thin glazing on the final layer (it is possible to accidentally take the glaze off with the varnish). Alla prima painting (what I’ll call “juicy” painting without getting overly impasto) is much more durable under such cleanings.

I personally try to dammar varnish my paintings after a year (and label the backs of the painting with technical information). I use a lot of coldpress linseed in my paints and I have noticed that my paint films seem to dry much more matte (dark colors really lose their saturation and value) than when before I used coldpress linseed. I also “oil in” often, which can lead to weird splotchy surfaces if I don’t oil in the whole painting each session. A thin coat of dammar varnish has really helped fix these problems for me without creating the super-glossy surfaces everyone associates with salon paintings.

The absolute worst examples of varnish abuse I’ve ever seen are at the Boston Museum of Fine Arts. All their Impressionist and Post-Impressionist paintings are (a) stuck into ornate fake Rococo frames, (b) hung in strong artificial light and (c) absolutely slimy with varnish.

They gleam, they shimmer, they shine; they look nothing like how the artists intended them to look. The paintings look like reproductions of themselves. In the Van Goghs the varnish on his ridges of impasto make irritating little points of light that bounce back at you and distort your viewing.

All the Barbizon School paintings, the Corots and Millets, are not only varnished but they’re glazed as well. The MFA says this is all to do with curation and preservation, I say its vandalism. Memo to curators: did the artist stick this picture in an elaborate golden frame and put glass over it? Did the artist slather it with shiny varnish? If the answer is no, then it should not be done –ever – because you, museum person, don’t know what the artist intended better than the artist did.

Thanks Joan, Mamie, and Neil for your comments about my new Varnishing article. I learned a lot through the research so hopefully this will be helpful to someone else too. I wish I had the problem of either selling or showing my work so quickly that I never get the chance to varnish but if I did have that problem then I would either suggest to the buyer to return to me in 6 months for varnishing or apply some retouch varnish (which can be applied when the painting is dry to touch as I understand it) Oiling out from what I’ve heard isn’t a very good substitute for varnishing as it will be harder to clean the painting when the time comes years later. Also while it may make the painting look better initially, give a uniform sheen and the like – I don’t think it will offer much protection to the paint surface. One last reply to Joan – The Art of Impressionism book is currently at 164.94 for the lowest price as a used book on Amazon. I may get this for myself this Christmas.