Gesso

From the Italian for gypsum or plaster. This is used in the making of grounds for painting. The traditional gesso is made from a combination of hide glue and whiting, sometimes with pigment added. It makes a smooth, hard non-yellowing surface that is very absorbent. This ground is only for rigid supports because it is brittle. There are other gesso grounds made of half chalk and half oil. These can be used on flexible surfaces. The most common use of the term "gesso" today, is in the acrylic gessoes. They are not as absorbent as the traditional ones, but are very strong and flexible. They can be used on any clean surface. They come ready made in various sized containers.