What is Gold Leaf Made Of?
The composition of gold leaf varies depending on the type. Real gold leaf is crafted from genuine gold, and can be mixed with small amounts of silver and copper to achieve different shades and karat values. It is valued for its longevity and resistance to tarnishing. Imitation gold leaf, however, is made from a combination of metal alloys like brass, copper, or zinc. These materials mimic the appearance of real gold but are more susceptible to tarnishing and require additional protective coatings to maintain their look over time.
How is Gold Leaf Made?
Gold leaf is made through a meticulous process called goldbeating. It starts with melting and casting gold into a bar or strip, which is then rolled into a thin ribbon. This ribbon is cut into smaller squares that are placed between layers of special paper and hammered until they reach the desired thinness. Finally, the thin sheets are cut to size and packaged for use in various decorative applications.
The process for making imitation gold leaf differs primarily in the materials used. Instead of gold, metal alloys such as brass, copper, or zinc are melted and cast into sheets. These sheets undergo a similar rolling and beating process but often require additional coatings to protect against tarnishing and to maintain their appearance over time.
What to Consider When Choosing Real Gold Leaf
There are two main factors to consider when choosing a gold leaf: its content/value and weight. Additionally, you should also consider the choice of adhesive size.
Gold Content
Gold content expresses the purity of the leaf and ranges from 6 karat to 24 karat, which is 100% gold. The degree to which the gold is mixed with silver or bronze will determine the karat value: silver will give a cooler tone and bronze a warmer tone. Gold content should be chosen in light of the project to be done, specifically whether the project is indoor or outdoor. All exterior projects should be gilded with gold leaf no less than 23.75 kt. Because gold is the noblest of metals, it is resistant to corrosion—the purer it is, the stronger it will resist rain, snow, sleet, and wind. Gold leaf of such value will maintain its integrity for 30+ years.
Interior projects, since they are not subject to climate changes, can be gilded with gold leaf of less than 23 kt. Typically, interior gilding of architectural features is 22 karat gold. The 21-22 karat range is good for interiors and has been used for centuries because it is extremely durable. The gold leaf used for interiors, if alloyed with other metals, can actually make it more durable to withstand general wear and tear and cleaning.
Weight
Gold leaf is weighed in grams per 1,000 leaves. The heavier the gold leaf, the more resistant it is to the climate and environmental issues. For this reason, a substantially heavy leaf is required for all exterior gilding projects—domes, statues, weathervanes, ornament. Typically, 18-23 grams per 1,000 leaves is recommended for exterior projects. As a studio, we will only use 21 or 23 grams. Interior gilding projects, however, are considerably less vulnerable to climate and environmental issues and are therefore better suited to use a lighter leaf.
Adhesive Size
An important note when it comes to gilding and the adhesive size you use.
For architectural oil gilding, the choice of adhesive size is crucial. Long size, or slow drying size, should be used for exterior applications due to its elasticity, as the extended drying time accommodates the expansion and contraction caused by changes in the climate condition. This flexibility ensures both the gold leaf and adhesive size are able to expand and contract with weather changes, maintaining the integrity of the gilding. In contrast, quick size, or short drying size, when used for exterior gilding, can result in a more brittle and less durable finish, potentially leading to a significant loss of gold leaf integrity after just one season, compared to over 30 years with the correct adhesive size.
