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  • Another Mt. Athos Icon QuestionApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2019-02-06 17:36:32 ... Most recent comment 2019-02-10 11:14:43
    Art Conservation Topics Egg Tempera
    Question

    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

Answers and Comments
  • ApproveRejectUn-ApproveUser Comment

    ​Fr. Ermaios clarified for me that the panels are in fact made from cedar backs (for a traditional natural wood look) faced with plywood (for stability).  I don't know if they cover the plywood with cloth before gessoing and painting; regardless, VOCs from the cedar seemingly can be ruled out.

    Instead, I have been pondering what might be the consequences of high humidity alongside the ocean?  Especially if environmental heat and humidity are on the rise? Salt water conducts, causes reactions, speeds up corrosion....Are there certain pigments (mineral, earth based) that might corrode or become transparent if exposed to high levels of salty humidity?  

    2019-02-08 08:33:51
  • EditDeleteModerator Answer

    ​Koo, these artists are clearly veyr lucky to have you as a consultant/advisor. You have basically covered all of the possible issues that may be the root of the problem when it comes to these slight color changes. Are these photos color corrected? That is a variable that can also through another monkey wrench into the discussion. Honestly, unless we could get some conservators out there to examine the paintings in person and then conduct a preventive survey of the humidity/temperature conditions some of their questions may remain unaswerable for the time being....that being said University of Delaware has a handful of students that would jump at the chance!

    Kristin deGhetaldi
    2019-02-08 23:41:05
  • ApproveRejectUn-ApproveUser Comment

    ​Hi Kristin,

    The photos haven't been retouched (in fact, the monk says the color change between the two icons is more dramatic in person than in photos).  I like diving into these painting puzzles, as they help me understand egg tempera better; and if circumstances and monastic rules permited I'd jump at the chance to go to Mt. Athos too!  Thanks for checking in on the mystery of the disappearing icon colors.  Koo

    2019-02-09 15:34:13
  • EditDeleteModerator Answer

    Koo

    I really have no answer to this delema. Earth colors would not chemically react in this manner. Perhaps there is some change in surface topography that appears as a change in color but this could only be checked in person. Otherwise, I am stumped.

    Brian Baade
    2019-02-10 10:46:11
  • EditDeleteModerator Answer

    ​One possible test that would interest me is the following: if they brushed a little water on a tiny area, do the colors get resaturated? Obviously it would be temporary but it would give a quick read of whether the colors could be revived. We have seen similar "fading" on exterior murals that was reversed with a varnish. The 'fading' in those cases were either a form of efflorescence or chalking, causing an overall dusty pale appearance, which the varnish would undo by being able to encapsulate the solids on the surface. Why it would happen with some of these icons but not others, I don't know, but certainly calcium carbonate has been tied to efflorescence and maybe there is some mechanism at work that is causing that to be driven to the surface. One aspect that might point to something like this - rather than color fading - is that the lightening of the colors seems both even and allover, which speaks to a general surface phenomena and not a pigment specific issue.

    Anyway, perhaps a stretch but something to perhaps try as a way to get more information given the difficulty of diagnosing this from a distance.

    Sarah Sands, Senior Technical Specialist, Golden Artist Colors
    2019-02-10 11:14:43
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