Gilding#Fire-gilding

Fire gilding is an operation carried out since ancient times until the 19th century, the most important and therefore the oldest known metal plating technology. The first known mention is found in the Naturalis Historia ( Natural History ), by Pliny.

Many historic fire gilding, even from ancient times are still very well preserved. Accordingly, the gilding in a very durable plating represents the incomparable soft rich luster get gilt pieces only through the elaborate hand polishing with polishing stones, and microscopic roughness of the metal surface are smoothed out. Above all articles of silver, copper, brass and bronze were gilt over the centuries. One of the most famous German, formerly fire-gilded statues is the " Golden Rider " in Dresden, August represents the strong and was unveiled in 1736.

Processing

When gilding a gold amalgam is used.

Gold amalgam can be obtained in various ways. For example, molten Feingold are approximately six times the amount of mercury added. But it is also possible that gold in the form of gold dust, foil or gold leaf over a low heat or simply by trituration in an excess ( six to eight times the amount ) to solve mercury. The resulting amalgam is a dough-like consistency at room temperature and melts now well below the melting point of gold.

Now, the degreased to be gold-plated metal surface and " mixed up ", that is immersed in water quick. These are used to prepare a solution of mercury in nitric acid. On the prepared goods can now spread ( eg with a brass wire brush ), the amalgam.

The amalgamated object is smoked over a weakly glowing charcoal fire while you spread the amalgam and smoothes. Usually, a rabbit's foot ( the dried hind leg of a rabbit ) was used. During the heating the parts of the gold amalgam diffuse into the base metal, while the largest part of the mercury evaporated. The surface is then due to its roughness is not gold shiny, but dull yellow. With polishing stones ( agate or hematite) can smooth the surface and bring to a shine.

Due generated during the fire gilding toxic fumes it was largely replaced by the galvanic gilding since the second half of the 19th century. Today, there are again some small businesses, the restore using the latest environmental technology and compliance with strict requirements for museums, churches and more and more for the art and luxury market with gilding and precious pieces finished.