Gilder’s Clay Base—also known as bole—is a clay-like substance. It is applied to the prepared surface, which is usually Gesso. Gesso is a mixture of chalk and Rabbit Skin Glue. The gilder’s clay layer and the underlying layer of Gesso create a suitable layer that allows the polishing of gold leaf with the Agate Burnisher Stone. The gilder’s clay base can only be used on absorbing surfaces. Both Lefranc gilder’s clay base and Kolner Classic Poliment are already processed with water to a paste, but you need to add some Rabbit Skin Glue to them first. Nazionale Bole is ready to be used.