Q: How do you use gold leaf? What is the difference between gold leaf and composition leaf? Are there any metallic paints that closely simulate the look of leaf?
A: Real gold leaf is actually high-carat gold, at least 22K, which is (still) beaten by hand into extremely thin sheets. The process involves interleaving the gold between sheets of parchment and beating this “book” with mallets. The resulting sheets are so thin that you can actually see through it if you hold it up to strong light. The fragility of these sheets makes handling it somewhat difficult. This may be less of a problem if you are attempting to gild relatively flat surfaces; in which case you can use “patent” gold, which is the same material lightly attached to a backing sheet of paper so that it may be transferred more easily. The loose-leaf gold must be used for more complex surfaces.
In either case, the surface is carefully prepared—which is a whole subject in itself: there are several different approaches, including one which involves applying layers of clay and burnishing it to achieve a polished effect in the gold. Every nuance of the surface is emphasized by the application of gold leaf, as well as every tiny imperfection.
A “size”—a varnish or glue—is applied as a very thin layer, preferably by spraying, and allowed to dry until tacky. If this is for an exterior application, an oil-based size is used over a water-resistant substrate. The loose gold leaf is picked up using a “gilder’s tip” which resembles a wide soft paintbrush. The tip is brushed on one’s hair to pick up a trace of oil, which allows the tip to adhere to the gold enough to pick it up, but still release it when the gold hits its target. The leaf is pushed into place with another soft brush, which is used to smooth out the sheet and remove any flakes of gold that did not adhere to the surface. This is where the extreme fragility of the material is an advantage; a precise configuration of size can be laid down with the confidence that it will be covered exactly to its edge and no further, since the gold will cleanly tear away from the areas that are not adhered.
The brilliance of real gold leaf cannot be matched by any paint, and as the gold does not tarnish this effect will last a long time. It is a physically delicate finish, however, due to the thinness of the gold itself, and will wear away from high spots if a gilded object is handled extensively or subjected to other friction. The gold should be used as a final layer—any clear coating will dull the finish considerably, making the result more resemble gold paint.
Composition leaf is made from various metals, and different colors are available: from copper, silver, and aluminum to various bronzes. The sheets are not as thin as real gold leaf, and are consequently much easier to handle. It is also cheaper, and comes in larger sizes; but it does not brush away from unsized areas as cleanly as real gold, nor does it have as brilliant an effect, even initially. It is, however, superior to any metallic paint in this respect, because it covers a surface with a continuous layer of metal, where a paint must rely on the collective effect of a series of particles. Unlike the real gold leaf, it will tarnish more or less rapidly, especially if used outdoors. If this is a concern, the color of the material may be preserved with a clear coating, with some sacrifice in brilliance. It is much easier to cut into shapes than real gold leaf, and is certainly a place to start, should one wish to experiment with this type of material.
by Andrew Werby