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What is Leaf?

Leaf is a very thin sheet of metal, usually of gold or silver, that is approximately one to two hundred nanometers thick. How thick is a nanometer? One nanometer is equal to one billionth of a meter. To use another approach, approximately one thousand sheets of leaf equal the thickness of a regular piece of paper. Leaf is used to decorate a variety of substrates, including metal and wood. (The wood frames around paintings are often gilded with leaf.)

The first step is to carefully smooth the substrate either by polishing or by painting the surface with several priming layers. Then, to adhere the leaf, an adhesive (glue) is often applied or, in a variation of mercury gilding on copper-based metals, mercury is brushed on and the object is heated. Because leaf is so thin, it cannot be handled. Instead craftspeople use a soft brush, as pictured above, or sometimes merely their breath to move leaf into position. The final step is to burnish (polish) the leaf using special tools to make the surface highly reflective. The burnishing ends of these tools consist of hard, highly polished stones of agate or hematite.

Eighteenth-century leaf gilding workshop. Etching from the Encyclopédie edited by Denis Diderot
and Jean le Rond d’Alembert (Paris, 1763)

Joan of Arc, gilded bronze

If you look closely at art that has been covered with leaf you may see areas where the sheets of leaf overlap. The detail of the statue of Joan of Arc reproduced below shows how this overlapping looks after it has weathered. These sections, having a thicker layer of metal, are better able to survive abrasive wear. Conservators often look for overlapping when determining whether leaf was used to decorate a work of art.

Detail from Joan of Arc
 

Historical and Modern Use of Leaf

Leaf application is an ancient technique that dates back at least four millennia. Not requiring a great deal of specialized equipment, this decorative method is still used by craftspeople and artists today. In addition to gold and silver, leaf is available in several alloys, with brass (an alloy of copper and zinc) the most frequently employed as it is an economical imitation of gold.

 

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