Facts
Oil Gilding
Breifly, after preparation (sanding, priming, base coats etc...) a slow or quick oil size is applied. Once the size is tacky the leaf is applied. Generally, cotton is used to burnish or shine the gold leaf. For gold leaf no protection coating is needed. For dutch (composition) gold a sealer is required so the dutch gold does not verdigris (oxidize).
Water Gilding
Water gilding is more complicated than oil gilding. After the surface is cleaned coats of gesso are applied to wood, stone, plaster etc... Once the gesso (base coat) is sanded, bole is applied. Bole is a mixture of clay and glue. After sanding the bole, water is applied to reactivate the glue. Next, the gold leaf is applied which sticks to the bole. Finally, burnish the leaf with a agate stone which shines the gold. Antiguing (patina) can then be applied over the gold leaf for period gilding.