Gesso is the primer coat applied to surfaces (e.g., raw canvas, paper, board, wood) and prepare them to receive and hold paint. Traditional gesso, which is used in oil painting, is made of white pigment, gypsum, and adhesive. Acrylic gesso is made of water-soluble acrylic polymer emulsion, white pigment, and fillers (e.g. chalk or silica). Gessoes give tooth and absorbency to the surface to ensure proper adhesion and reduce the risks of cracking, flaking, or peeling. The gesso dries to create a flexible, durable, and adhesive ground that is suitable for most water-soluble media.
Acrylic gesso comes in white, clear, carbon black, and a variety of colours. The texture, fluidity, opacity, and coverage of acrylic gesso in the market may vary according to grades and brands. If applied correctly, acrylic gesso is an acceptable ground for oil paint; however, there are ongoing discussions (due to lack of data) on how the use of acrylic gesso with oil paints may impact the ageing process. Acrylic polymer emulsion has been used in the manufacture of artist materials only since the 1950s; therefore, there is insufficient data to determine, in particular, the following concerns: oil penetration to the substrate, discolouration, lack of adhesion, and cracking.
Acrylic gesso is intended to be used with acrylic paints, casein, and egg tempera; it's not suitable for watercolours or gouache; it does not have sufficient absorbency for adhesion and will cause lifting when blending and layering. There are specially formulated acrylic-based grounds for watercolour and gouache.