What is Gesso...?? Gesso is a white, plaster-based substance used to prepare or “prime” surfaces for painting. Benefits of Gesso - The purpose of gesso is to provide a smooth, primed surface for painting. This creates an ideal base for artists to work on, providing them with a smooth (or textured) surface that allows their brushstrokes and colors to stand out more clearly than they would on untreated canvas or wood and save on paints since you won’t need as many layers to cover the canvas surfac