very obscure question - but i'll try anyway

dorkkarl

in the mid 1800's, there was a specail mint process called "fire-gilt" processing which took normal bronze and made it appear to have a light-gold color. has anyone ever heard of this process, or know of any references to it? its an obscure topic, & i'd appreciate any information or research leads whatsoever.

thanks.

K S

kranky

For metallic objects, or objects that can stand high heat, the artisans of the Middle Ages used a method for gilding that is still one of the best methods for gilding that has ever been devised. It is described here for historical completeness ONLY. The method is very dangerous and should only be attempted by persons having access to a laboratory fume hood with a liquid nitrogen gas trap on the exhaust, and facilities for the safe disposal of hazardous wastes.

Mercury will combine with gold to form an amalgam. To gild a metal object, such as a bronze chalice, the medieval workman would clean its surface thoroughly and then rub mercury all over it. The workman would then lay leaves of gold all over the surface. The gold will alloy with the mercury, forming an amalgam layer on the surface. If the object is heated to a temperature near the boiling point of mercury, but below the melting point of gold or the base metal, the mercury will evaporate, leaving a fine, thin layer of gold. The process is called "fire gilding" and is still the gilding method giving the finest results.

The only problem is that mercury vapor is intensely poisonous, and can be ingested through the lungs, mouth, or even skin. Its effects are cumulative over life, and can never be reversed. Fire gilding is against federal law for commercial use in the United States, and is illegal for any use in most states.

[Copied from here]

dorkkarl

thank-ye, kranky! i will use that as a starting point for my research. for anyone wondering why i'm interested, i just bought (cherry-picked big-time) a rare federal mint medal that looks like an original strike, only it appears to be fire-gilt, instead of bronzed. an esoteric subject, but all the attrib'd ones i've run across were worth 100's of $, & just stole this from a pawn broker for 20 bucks!

K S