Gesso is a type of primer or painting ground. The word 'gesso' is the Italian word for gypsum, a component of painting grounds on wood panels of medieval and Renaissance paintings. The primer is a base coat that creates the foundation for a painting. Formerly the word gesso defined grounds made with animal glue derived from parchment cuttings and gypsum or chalk. The contemporary use of the word 'gesso' refers to a primer or painting ground consisting of a white pigment, fillers, such as chalk, and a binder. Acrylic paint manufacturers promoted the use of the word gesso for their acrylic dispersion grounds. However, there is no gypsum in most acrylic grounds today, but manufacturers continue to use the term to designate their commercial acrylic primers. To distinguish traditional gesso made with animal glue and gypsum or chalk, we use the term 'glue ground' on this website. On this website, 'acrylic gesso' is called 'acrylic ground.'