The polished surface is made smoother and lighter by chalking.
To lighten the surface, chalk powder (Calcium carbonate CaCO3 containing various salts of magnesium and calcium) was rubbed into the damp skin. This helped to make the surface stronger and whiter. In the case of careless processing, the chalk powder covered the surface unevenly and left a slightly linear texture on the surface.
An especially white and high-quality surface was achieved when a paste-like mixture of chalk, egg whites, flour and milk was used.