Gesso is an important art supply to get your canvas ready for painting. You can buy gesso readymade from any art supply shop. 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.