Material & Techniques

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.

Gouache paint consists of ground powdered pigments suspended in a water-soluble binder; it’s the opaque version of watercolour paint. Not unlike watercolours, gouache paint is a combination of pigment, gum arabic (binder), various plasticizers, and preservatives. The opacity in gouache is achieved by adding chalk or white pigment. Gouache has a very matte finish and the appearance of tempera. Water is used during application and when it evaporates, the binder fixes the pigments to any surface suitable for watercolours.

Gouache is re-wettable and reworkable like watercolours; however, it dries much faster than watercolours. The main difference between gouache and watercolours is a wet-to-dry colour shift. There is usually a slight change in hue between the wet and dry stages. This may pose a challenge when it comes to colour matching. Gouache has the characteristics of both acrylics and watercolours. Like acrylics, it has good coverage and like watercolour, it is reworkable and can be used to depict minute details. For those reasons, gouache is preferred by commercial artist and illustrators for creating posters, illustrations, and comics.

Acrylic gouache, which has all the qualities of traditional gouache, uses acrylic polymer emulsion as a binder. That means it is water-resistant once dry; there is no bleeding or lifting when rewetted or layered.

Acrylic mediums are added to acrylic paint to change its character or behaviour during the painting process.

A gloss medium is used to increase transparency, sheen, and luminosity while a matte medium is used to reduce sheen and make colours look flat. A glazing medium, which reduces opacity and increases transparency, is suitable for glazing and layering techniques. Gel mediums are used to increase body and make the paint retain brush strokes. Modelling paste works in the same way as gel mediums but is thicker and can be used to create a 3D finish.

Texture mediums change the surface appearance of paint by imitating ceramic stucco, sand, glass bead, and more. Airbrush mediums, apart from being used for airbrushing technique, can be a good painting tool to dilute paint to a fluid consistency or create watercolour-like washes.