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?
Koo
My experience is that isolating the very porous, high PVC surface of egg tempera greatly facilitates the application of oil, oil glazes and varnishes. I understand it is a complicated topic in that isolators bind with the underlying tempera layers and are not readily (if at all) removable. However without an isolator, oil glazes sink in (sometimes terribly so) and can be very slow to dry; and/or varnishes sink in, bind with the tempera and become virtually unremovable.
In other words, I have yet to find a way around the challenges posed by layering additional materials on top of absorbent, porous egg tempera – except, of course, not to add anything on top. But that either defeats an artist’s intent and/or leaves a tempera painting more vulnerable (because it is unvarnished).
All this came up because I’m conversing with a painter from England and – well, it’s a complicated topic, so I think I’ll create a separate post for it and keep this post focused on the issue of isolators.
Koo
Hi Brian,
I’m surprised to hear that glair (water-based) was used over oil, a curiosity how they got it to behave and adhere. Thanks for the book reference, I hope to read it at some point (although at $345 it is currently relegated to my wish list).
In “A Conversation on Painting Techniques, Alfio del Serra, The Burlington Magazine” the author mentions that, over time, egg white becomes very grey. I’ve also read it can become cloudy, brittle, difficult to remove. Is all that accurate? Would you say that, although glair was used in the past as an isolator, at this point, given other options (like B72) it’s not a good choice?
Thanks as always for your insights – I’m very appreciative that MITRA exists and of the work that goes into it.
Koo
I do not share those concerns. However, I do wonder about the function and need for the isolation layer. Is this to facilitate later oil or glaze applications?
I believe that I covered these topics (to the degree that I am able) in your other thread. As you would expect, I offered no magical panacea. As I suggested there, I would prefer a solvent born isolating layer over an aqueous or dispersion layer for exactly the reasons you suggest.
On the other hand, we do know that glair (egg white varnish) was used over egg tempera and later oil paintings from the middle ages on. (see The Conservation of Easel Paintings ed. By Stoner and Rushfield)
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