Fire gilding

Fire Gilding

Fire gilding, also known as mercury gilding, is an ancient technique used to apply a thin layer of gold to the surface of an object. This process involves the application of an amalgam of gold and mercury to the object, followed by the application of heat to evaporate the mercury, leaving behind a layer of gold. This method was widely used until the 19th century, when its health hazards became more widely recognized.

History

Fire gilding has been used since antiquity, with evidence of its use dating back to the 4th century BCE. The technique was popular in Ancient Rome, where it was used to gild bronze statues and other decorative items. During the Middle Ages, fire gilding was employed extensively in the creation of religious artifacts and jewelry.

In the 18th and 19th centuries, fire gilding was commonly used in the production of Ormolu, a type of gilded bronze used in decorative arts. However, the process was eventually supplanted by electroplating due to the health risks associated with mercury exposure.

Process

The fire gilding process involves several steps:

1.Preparation of the Surface: The object to be gilded is cleaned and sometimes roughened to ensure good adhesion of the gold. 2.Application of the Amalgam: A paste-like amalgam of gold and mercury is applied to the surface of the object. This amalgam is typically prepared by mixing finely powdered gold with mercury. 3.Heating: The object is then heated, often in a furnace, to evaporate the mercury. This leaves behind a thin layer of gold bonded to the surface. 4.Burnishing: The gilded surface is polished to enhance its luster and smoothness.

Health Hazards

The primary health hazard associated with fire gilding is mercury exposure. Mercury is a toxic element that can cause serious health problems, including neurological damage. During the heating process, mercury vapors are released, posing a risk to those performing the gilding and to the environment.

Due to these risks, fire gilding has largely been abandoned in favor of safer techniques such as gold leaf application and electroplating.

Modern Use

While fire gilding is rarely used today due to its health risks, it is still employed in some traditional crafts and restoration projects. In these cases, strict safety measures are implemented to protect workers from mercury exposure.

Also see

• Gold leaf
• Electroplating
• Ormolu
• Mercury poisoning