Charbonnel Burnishing Clays - Many traditional gilders will use burnishing clay also known as Bole as a base for gilding. The procedure is to mix one part clay to two parts of a warm rabbitskin glue size. This mixture is then applied to a super smooth surface. After the clay solution dries it is burnished and gilded. The color of the clay becomes visible through the fine leaves of gold. The black is shown here in the photo; the clay also comes in red (red earth) and yellow (yellow ochre).