The Technique of gilt bronze in the 18th and 19th century

First and foremost there is a model, usually a drawing.
A sculptor makes a
clay or wood model.
The piece is then given to the "fondeur ciseleur" (chaser) who melts then chisels.
The most delicate parts are
directly assigned to the "ciseleur doreur" (carver -gilder).
These two communities,
"fondeur ciseleur" and "ciseleur doreur", frequently argued about their respective rights, some "fondeur ciseleur" sometimes taking care of the gilding.

Louis XVI arbitrated by bringing them together under the banner of a single corporation.
It is then the phase of the gilding itself.

There are two operating modes: ormolu and gold leaf.

1) The
ormolu : gold lime reduced or "ground" on a grinding stone is amalgamated with mercury or quicksilver.
This mixture heated in the crucible is applied to the bronze with a brush.
The bronze is then deposited on a grid and the evaporation of mercury allows the attachment of gold to the bronze.
These mercury vapors are very toxic.
Then come hammering, burnishing and setting color of gold, operations which give all its nuances to the gilding.
The transitions between matte and shiny parts are merged seamlessly.

2) The gilding with gold leaf: If the gold leaf does not contain mercury, this metal should be applied on the piece to brown, and the risks were identical.
Indeed, gold is attached to the bronze on evaporation of mercury.
One or two very thin gold leaf placed on a pad were applied by brush on the blue piece in the fire.
The finish was the same as for gilding with gold ground.

Another technique was that of bronze varnish or "set the color of gold." Novices falsely call these pieces "gilded bronze".
They were taken just after the cast (the "réparure"), then were immersed in the etching (the acid).
They finished by covering with a protective varnish.

The nineteenth century saw the emergence of the gilding by electrolysis, invented in 1827. Its advantage was the absence of toxic vapors for artisans.