Updated: Jan 27
Gesso is the primer coat applied to surfaces (e.g., raw canvas, paper, board, wood) to prepare them for painting. Gesso gives tooth and absorbency. Acrylic gesso consists of water-soluble acrylic polymer emulsion, white pigment, and fillers (e.g. chalk or silica); it 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. Texture, fluidity, opacity, and coverage 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 it may impact the ageing process, in particular, oil penetration to the substrate, discolouration, lack of adhesion, and cracking.
Oil and alkyd-based gessoes are more appropriate grounds for oil paintings. Oil gesso is made from drying oil, white pigments, and fillers. Alkyd gesso substitutes the oil with alkyd resin. Oil and alkyd-based gessoes are not suitable for water-soluble media.
Universally prepared acrylic gesso is not sufficiently absorbent for watercolour and gouache. The lack of absorbency weakens adhesion and causes lifting when blending and layering. One solution is to apply high absorbency mediums over the gessoed canvas to create a porous and paper-like surface. Alternatively, there are specially formulated acrylic-based grounds for watercolour and gouache.