This basecoat can be used to prime any surface when applying metal leafing sheets. Traditionally, undercoating has been applied for both form and function. Because leafing requires a non-porous surface, undercoating’s often act as a sealant. It also provides an additional color enhancement or tint to the applied leaf.
Red Oxide was used as the traditional undercoating by master gilders because it brought out the brilliance of the gold leaf, and since leaf is thin, it was often burnished and sanded to let the undercoating show through. This technique is often referred to as Old World gilding.