Apply gesso primer to unprimed canvases, panels, and boards to create a more absorbent surface and better adhesion for oil and acrylic paint. Gesso also adds tooth or texture to canvas. Originally made for oil painting, gesso paint is typically made of paint pigment, chalk, and binder — traditionally animal glue binder.
Today, gesso is often made of an acrylic polymer medium as its binder rather than animal glue. Acrylic binder provides a more flexible surface and creates a painting that is easier to maintain. Acrylic gesso also includes a pigment — usually Titanium White. Primer and gesso can be tinted with paint.
Gesso isn’t needed for primed canvas, which is already coated with gesso.
Acrylic gesso is primarily intended for acrylics, oils, and alkyds. There are acrylic-based watercolor grounds and other absorbent grounds that provide the ideal surface for watercolor and ink. Pastel grounds are specially designed to provide the right tooth and texture for pastel artwork. Encaustic should not be applied on acrylic gesso except for specially formulated encaustic gesso. Acrylic gesso is not considered absorbent enough for egg tempera.