or moulu

Or moulu is French for 'ground gold' — or (gold) and moulu (ground, past participle of moudre). The technique is mercury gilding: gold is dissolved in mercury to form an amalgam, the amalgam is applied to a bronze object, and the piece is heated until the mercury vaporizes, leaving a thin gold layer bonded to the bronze. The gold surface is then burnished to a high shine. The French called the result bronze doré or or moulu. English borrowed it as ormolu.

The technique reached its peak in eighteenth-century France. Gilded bronze mounts — handles, escutcheons, clock cases, candelabra — were the signature decorative elements of French furniture from Louis XV through the Empire period. The greatest ormolu workers — Pierre Gouthière, Pierre-Philippe Thomire — were celebrities of the decorative arts. Gouthière's ormolu work for Marie Antoinette's rooms at Versailles is still considered the finest ever produced. The gold surface is so even, so brilliant, and so precise that the mounts look dipped in liquid gold.

Mercury gilding killed the workers. The vaporized mercury attacked the lungs and nervous system. French gilders in the eighteenth and nineteenth centuries had short life expectancies. The golden surfaces of Versailles carry an invisible human cost that the word ormolu does not contain. In 1830, France banned mercury gilding. Electrogilding, developed in the 1840s, replaced it — a safer process, but ormolu purists still consider the mercury method superior. The original method produces a thicker, more durable gold layer.

The word ormolu now refers broadly to any gold-finished bronze, regardless of the technique used. Antique dealers use it to mean genuine mercury-gilded bronze. Furniture catalogs use it to mean gold-painted zinc. The word has blurred, but the original objects have not — an eighteenth-century ormolu clock mount, properly maintained, will still shine after 250 years.