Ormolu

Ormolu – (from French ‘or moulu’, meaning ground or pounded gold) is an 18th-century English term for applying finely ground, high-carat gold in a mercury amalgam to a bronze object.The mercury is burnt off in a kiln and the gold-coloured veneer left behind is known as ‘gilt bronze’.

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 mercury is then burnt off through exposure to extreme heat, leaving the gold adhered to the metal object.

No true ormolu was produced in France after around 1830 because legislation outlawed the use of mercury which is a toxic metal. Therefore, other techniques had to be used instead but nothing surpasses the original mercury-firing ormolu method for richness of colour and durability.

The most common modern technique for producing the effect is electroplating. Silver-gilt (vermeil) is produced in the same way using similar techniques