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Question asked 2016-11-03 11:02:36 ...
Most recent comment 2016-11-03 13:03:00
Dyes
Gilding
Varnishes
In some Russian icons of the 18-19 cc, there was a method of "gilding" without gold leaf. Metal leaf (often silver leaf) was used, but then coated with a yellow-tinted varnish. It didn't look like gold but had its own distinct charm and softness.
Recently, I tried to replicate this technique by using aluminum leaf; however, I cannot find a suitable colorant for the varnish. Kremer Pigments suggested something (organic pigments) but these turned out to be not soluble in a solvent-based varnish. Even though the pigments were transparent, the varnish turned cloudy, just like you'd add a mineral pigment such as yellow ocher into any liquid.
Is there a type of dye that one can be completely dissolved in mineral spirits (i.e., solvent-based polyurethane varnish)?
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Moderator Answer
(Baade, Brian)
It was very common in the 19th century (actually this was done for centuries) to tone silver or tin leaf to resemble gold. 19th-century recipes often call for the application of a colored resin solution (lemon shellac, etc) as a surface coating to both seal in the leaf from oxidation and to impart the gold-like color. The alcohol soluble yellow resin gamboge could be added to contribute a very brilliant yellow tone. The problem with these methods are that the colorants are quite fugitive to light.
Choosing lightfast pigments like yellow ocher makes good sense from a preservation standpoint. The problem is at most pigments (as opposed to dyes and soluble resins) create a far more turbid solution and coating than varnishes tinted with dyes. Pigments are colored particles that are insoluble in their binder while dyes and colored resins are colored materials that dissolve in their binder or solvent. It is still possible to use pigments in this capacity but one should choose those that are the most transparent and very finely ground.
If you are hoping for a completely transparent effect that actually mimics gold leaf, I think that you would want to find a dye that is both relatively lightfast and is soluble/compatible in the varnish system that you intend to use (i.e. alcohols or hydrocarbon like mineral spirits).
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