Modern gilding is applied to numerous and diverse surface and by various processes; those used in modern technology are described in gold plating. more traditional techniques still form an important part of framemaking and are sometimes still employed in general woodworking, cabinet-work, decorative painting and interior decoration, bookbinding, and ornamental leather work, adn in the decoration of
pottery, porcelain, and glass.
Mechanical gilding
Mechanical gilding includes all the operations in which gold leaf is prepared, and the processes to mechanically attach the gold onto surfaces. The tecnique include burnishing, water gilding and oil-gilding used by wood carver and gilders; and the gilding operations of the house decorator, sign painter, bookbinder, the paper stainer and several others.
Polished iron, steel and other metals are gilded mechanically by applying gold leaf to the metallic surface at a temperature just under red-hot, pressing the leaf on with a burnisher, the reheating when additional leaf may be laid on. The process is completed by cold burnishing.
"Overlaying" or folding or hammering on gold foil or gold leaf is the ismplests and most ancient method, and is mentioned in Homer's Odyssey, even in Old Testament.
The next advances involved two simples processes. The first involves gold leaf, which is gold that is hammered or cut into very thin sheets. Gold leaf is often thinner than standard paper today, and when held to the light is semi-transparent.
Gilding on canvas or on wood
If gilding on canvas or on wood, the surface was often first coated with
gesso. The "gesso" is a substance made of finely ground gypsum or chalk mixed with glue.
Once the coating of gesso had been applied, allowed to dry, and smoothed, it was re-wet with a sizing made of
rabbit-skin glue and water ("water gilding" whichc allows the surface to be subsequently burnished to a mirror-like finish) or boiled linseed oil mixed with lithearge ("oil gilding", which does not) and the gold leaf was layered on using a gilder's tip and left to dry before being burnished with a piece of
polished agate.
Those gilding on canvas and parchment also sometimes employed stiffy-beaten egg whites, gum, or
gilding bole as sizing, though egg whites and gum both become brittle over time, causing the gold leaf to crack and detach, and so honey was sometimes added to make them more flexible.
Using the gold as pigment
Other gilding processes involved using the gold as pigment in paint: the artist ground the gold into a fine powder and mixed if with a binder such a gum arabic. The resulting gold paint, called shell gold, was applied oin the same way as with any paint. Sometimes, after either gold-leafing or gold-painting, the artist would heat the pieces enough to melt the gold slightly, ensuring an even coat. These techniques remained the only alternatives for materials like wood, leather, the vellum pages or illuminated manuscripts, and gilt-edged stock.
