Gilding in its traditional sense means covering a surface with sheets of Gold Leaf. Broadly one differentiates between oil and water gilding techniques. This was a craft and skill that had to be acquired through rigorous training. After three years of a guilder’s apprenticeship one could call oneself an apprentice and still many years away from being a master.
In about 1840 in Nuremberg Germany, in the midst of the Industrial Revolution, Henry Bessemer invented the mechanized process of manufacturing bronze powder.
After intense research, Bessemer began manufacturing and marketing “a gold paint” which he stated “would preserve the gold colour for as long as possible” at much cheaper prices.
This paved the way for the layman to produce look alike gilded surfaces in a fraction of time for a fraction of the price and was extensively used to fix the odd blemish on the golden picture frame.
However – not all that shines is gold.
This fact of life came to the fore a few years later.
Gold bronze paint is made up of tiny flakes of Brass, Zinc or Copper (depending what shade of gold is required) and was then mixed with a binder. The binding medium can be shellac and other natural resins, oil, cellulose-nitrate based lacquers, and other synthetic polymers based lacquers (polyurethane, acrylics,etc.).
However – Brass, Copper and Zinc are metals that tarnish easy.
An oxidization process aided by the sulfur content in the air darkens the color of the metal and after a few years what once looked like gold had turned into a greenish brownish mess.
Repair work executed with gold bronze paint is not of a durable nature and will cause more damage than cure.
The following pictures illustrate to what extend gold bronze paint can discolor over a period of time.