Hello Mitra,
Among the questions the Mt. Athos iconographer sent me, what follows is the most vexing. It is also very complicated. His email explanation was very long, so I have extracted the main points below.
The Problem
The workshop has a large icon production, each monk using same materials and procedure. About 3 years ago some icons appeared "faded" (not sure if icons are literally losing pigment particles or pigments losing their color). See images, attached. On left, icon in good shape; right, icon with diminished color. He says they appear worse in person.
Mt. Athos Icons, 1.pngMt. Athos Icons, 2.pngMt. Athos Icons,3.png
- The color change takes place within 3-6 months after completion.
- Does not occur on all icons
- Occurs on both unvarnished and varnished icons.
- Occurs mostly on large icons.
Materials & Methods of Workshop
- Use Cedar Wood Panels
- Traditional Gesso with 100-300 bloom strength glue
- Use pigments that are, in his words, "dried out, old, cheap"
- Use premade (by the monks) mixes of 6 to 8 pigments for flesh and other areas
- 1 part egg to 1 part vinegar medium
- Hard, tap water to thin paint
- Would often thin tempered paint with water considerably
- Finished with Lauscaux Acrylic Varnish
- Very humid environment
Changes
In an effort to solve the problem, they made the following changes:
- Replaced all pigments with new colors from good companies
- Simplified premixes of color to just 2 pigments (i.e. flesh = Iron Oxide Yellow from Schminck, Eisen Oxide Orange from Kremer)
- No vinegar in medium
- Replaced tap with distilled water
- Not thinning tempered paint with water anymore
Once they made the above changes, the problem decreased 80% but is not entirely gone.
My Comments
I have a few comments on their practices:
- Use a 450 bloom strength, 100% collagen glue in gesso.
- If working with pigment pastes, be attentive to the potential for mold (i.e. if pastes are partly drying out & sitting for a while)
- Pigment age isn't an issue (they don't become "old") unless they are (a) in a hydrated/semi-moist state (can cause mold), or (b) a fugitive color, which can be affected by UV light (work with ASTM Rated III colors).
- A "cheap" pigment isn't necessarily bad, many earth colors are very inexpensive. However important to buy from a reputable supplier of artists pigments that can give specifics (origin, lightfast rating, toxicity, etc).
- Complex premixes of color are fine. However greater complexity in a system = greater chance of problems, harder to diagnose source of problem. Nonetheless, doesn't mean a complex system can't be successful.
- Mineral pigments are most stable.
- Vinegar can act as a preservative but it's acidity may affect some colors. Better to nix vinegar and just start with fresh egg (as they are now doing).
- Once paints tempered properly (correct ratio of yolk to pigment) can thin tempered paint with more water to affect working properties. In fact, would be unnecessarily very limiting to work only with paint of all the same density.
However, if you significantly thin tempered paint with water, at some point the binder (egg yolk) is so dispersed, that it becomes necessary to add a drop or more yolk medium to paint. There isn't a precise formula for when more yolk is needed in very water-thinned paint, more of a feeling; i.e. when paint feels like watercolor instead of a bodied, egg-based paint, add bit more yolk to the paint.
Explanation for Changed Colors
While I think the icon workshop could (or already has) improve some of their practices, none seem to explain the change in appearance of the icons. I don't even understand what's happening to the color! Given that some varnished icons faded as well, I don't think they could be literally losing pigment (as a varnish wouldn't permit that); it seems more likely pigments are losing color.
The two things that strike me as potentially problematic are (a) the high humidity in their region, and (b) the cedar panels. I was struck by the response to an earlier question I posed which mentioned VOCs emitting from cedar can affect metallic colors - might the VOCs be turning some pigments transparent? If so, why some icons but not all - different wood & atmospheric conditions?
So I'm puzzled by his dilemma and welcome any ideas. I also welcome response to my comments to the workshop to improve their practices.
Thanks,
Koo Schadler
