Gesso is a pretty simple material—it was originally made from a mixture of chalk or plaster and glue. In fact, the word "gesso" stems from the Italian word meaning "chalk."
Gesso is used in painting as a preparation for any number of substrates such as wood panels, canvas and sculpture as a base for paint and other materials that are applied over it. The colour of gesso is usually white or off-white.
Gesso is very similar to white acrylic paint, only thinner. It dries hard, making the surface more stiff. Gesso prepares (or "primes") the surface for painting, making the surface slightly textured and ready to accept acrylic paint. Without gesso, the paint would soak into the weave of the canvas.
What is Gesso: Everything You Need to Know About How to ... - Art is Fun
Traditional gesso, or genuine gesso, is a mixture of hot animal glue (usually rabbit skin glue) and gypsum applied to a stiff surface in several layers while it’s still warm.
What Is Gesso? Why It’s A Must For Every Artist - Art Ignition
This guide covers gesso basics: types, application techniques with brushes, recommended coats for acrylic and oil paintings, drying times, canvas priming importance, and tips for reusing canvases effectively.
Gesso, fluid white coating, composed of plaster of paris, chalk, gypsum, or other whiting mixed with glue, applied to smooth surfaces such as wood panels, plaster, stone, or canvas to provide the ground for tempera and oil painting or for gilding and painting carved furniture and picture frames.
Gesso is a white, plaster-based substance used to prepare or “prime” surfaces for painting. The purpose of modern gesso is the same as traditional gesso: to provide a smooth, primed surface for painting.