The manufacture of true ormolu employs a process known as mercury gilding or fire gilding, in which a solution of nitrate of mercury is applied to a piece of copper, brass, or bronze, followed by the application of an amalgam of gold and mercury. The item was then exposed to extreme heat until the mercury burned off and the gold remained, adhered to the metal object. Most mercury gilders died by the age of 40 due to exposure to the harmful mercury fumes. This gilding technique is similar to that also used on silver, which produced silver-gilt objects known as vermeil.
"Hang him; a gilder that hath his brains perished with quicksilver is not more cold in the liver".—John Webster, The White Devil, 1612.
The principal use of ormolu was for the decorative mountings of furniture, clocks, lighting devices, and porcelain. The great French furniture designers and cabinetmakers, or ébénistes, of the 18th and 19th centuries made maximum use of the exquisite gilt-bronze mounts produced by fondeurs-ciseleurs, or "founders and finishers", such as the renowned Jacques Caffieri, whose finished gilt-bronze pieces were almost as fine as jeweler's work. Similarly fine results could be achieved for lighting devices, such as chandeliers and candelabra, as well as for the ornamental metal mounts applied to clock cases and even ceramic pieces. In the hands of the Parisian marchands-merciers, the precursors of decorators, ormolu or gilt-bronze sculptures could be used for bright, non-oxydizing fireplace accessories or for Rococo or Neoclassical mantel or wall-mounted clock cases (a specialty of Charles Cressent), complemented by rock-crystal drops on gilt-bronze chandeliers and wall-lights.
The bronze mounts were cast by the lost wax method, and then chiselled and chased to add detail. Rococo gilt-bronze tends to be finely cast, lightly chiselled, and part burnished. Neoclassical gilt-bronze is often entirely chiselled and chased with extraordinary skill and delicacy to create finely varied surfaces.
Chinese and European porcelains mounted in gilt-bronze were luxury wares that heightened the impact of often-costly and ornamental ceramic pieces sometimes used for display. Chinese ceramics with gilt-bronze mounts were produced under the guidance of the Parisian marchands-merciers, for only they had access to the ceramics (often purchased in the Netherlands) and the ability to overleap the guild restrictions. A few surviving pieces of 16th-century Chinese porcelains respectfully mounted in contemporary European silver-gilt, or vermeil, show where the foundations of the later fashion lay.
From the late 1760s, Matthew Boulton and James Watt of Birmingham produced English ormolu vases and perfume-burners in the latest Neoclassical style. Though the venture was never a financial success, it produced the finest English ormolu.