fire gilding

Mr. McLemore practiced the ancient method of fire gilding, in which mercury and gold are heated to an extreme temperature, causing the gold to transfer onto an object — in his case, mostly antique clocks.

Eric Thiriet, who specializes in finishing techniques, and Marc Voisot, a restorer who works with fire gilding, huddled head-to-head before a golden column and capital at the entrance to the exhibition, whispering in low conspiracy about its detail.

Fire gilding, specifically, is now rarely used except in museum-piece restorations.

In Gouthière’s workshop, gilt was applied with fire gilding, a process by which an amalgam of mercury and gold was gently baked onto an object in a low fire, the mercury evaporating and the gold remaining as a coating of gilt.

Electroplating — using an electric current to adhere the gold to the object — appeared in the 19th century, largely replacing fire gilding, whose mercury fumes are highly toxic.