Gold leaf is an ultra-thin layer of pure gold used by crafters to create a gilded appearance on projects such as picture frames, sculptures and book bindings. The application of gold leaf through a process known as water gilding can be very labor-intensive and challenging for beginners. Gold leaf is extremely fragile by nature, and will adhere to almost any moistened surface. Professional gilders suggest it could take months of practice to become proficient at handling gold leaf.

Since pure gold is an element, not a compound or alloy, it can be compressed to nearly the atomic level without destroying its structure. This means gold could literally be pounded in a layer so thin sunlight could pass through it. This property of gold is essential to the creation of gold leaf. During ancient times, craftsmen would create gold leaf by placing a quantity of gold between two leather straps and pounding it by hand for weeks or months until the gold became exceptionally thin. The gold leaf could then be applied to paintings, sculptures and other religious or royal artifacts.

The modern method of creating gold leaf involves the use of metal rollers capable of compressing gold to a thickness of only 1/250,000th of an inch. The finished gold leaf can be cut into small sheets and sandwiched between layers of glassine paper, one of the few substances to which gold leaf will not adhere. Gold leaf is often sold in craft stores as one large sheet or in layers separated by glassine paper. Those who work with gold leaf may also invest in a special fan brush or comb used to transfer the gold leaf from the paper to the project.

When working with gold leaf, it is important to remain exceptionally patient and to have the proper tools and materials at hand. Preparing a project for water gilding often involves building up the surface by applying several layers of gesso, a material used by artists to create texture on canvas. After building up the surface with gesso, another material called a bole is applied to the object to be gilded. This bole is a mixture of clay and water, which provides an adhesive layer for the gold leaf. Because water must be on the surface of the bole precisely when the gold leaf is applied, the gilder must work quickly and deliberately.

Gold leaf can be cut into smaller pieces with a special knife, but it does tear very easily. An entire sheet of gold leaf can be applied through a delicate process involving a gold leaf comb and a substance like petroleum jelly. The gilder places a very small layer of petroleum jelly; on the back of one hand, and uses the other hand to sweep the gold leaf comb lightly through it. The comb or fan brush is then carefully placed over the gold leaf itself, with the petroleum jelly; providing just enough adhesion to lift it from the glassine paper. The gold leaf is then transferred to the moistened surface of the project and allowed to adhere.

Any excess gold leaf can be brushed off with a very soft brush and saved for future use. The applied gold leaf is often burnished with a special stone attached to a brush handle. The bole itself may also be tinted to provide a contrasting or complementary undertone to the gold leaf. A layer of red or yellow might enhance the shimmer of the gold leaf, while a black layer might give the burnished piece an antique or distressed appearance.

Because working with actual gold leaf can be an expensive and labor intensive process, many crafters now use gold paint to duplicate the gilding process. By using a flat black undercoat and judicious burnishing, a skilled crafter can create a very convincing gilded effect without using real gold leaf.