Preparing your canvas for painting

A small section of artists paint in oil or acrylic on unprimed paper, canvas or wood but for the most part, artists prepare their surfaces for painting. If you don’t prepare canvasses:

• Acrylic paint: Canvas will be bumpy and can repel water causing paint to bead rather than flow.
• Oil paint: Canvas will be bumpy and can soak up oil and produce outlines around painted areas or leave paint crumbly.

Unprimed paper may absorb the oil or buckle from too much water and wood might absorb paint unevenly in the grain and swell due to absorbing water. Fortunately, there are surface treatments to ensure they’re easier to paint on and last longer for permanent paintings:

Size (sealant)

This sealant helps watercolour and acrylic paint sit atop the surface rather than the moisture being absorbed into the fibres where it will end up looking dull and washed out. Size also hardens the canvas so there isn’t as much give. Reducing the flexibility of the canvas means easier paint strokes and more finessed mark making. On wood, adding size events out absorption and prevents excessive moisture from entering.

Primer

A primer is an adhesive that adheres to a surface better than your paint would. Without a primer, it would flake off if rubbed or scratched and may peel after drying. Especially if in direct sunlight. Primers will increase the longevity of your finished product. Most off-the-shelf stretch canvases come with an all-purpose primer, which means they have an acrylic base so they can be painted with oil or acrylic paint. 

Gesso

Gesso is the traditional method and refers to the mixture of hot animal glue and gypsum (chalk), applied in many thin layers to wooden panels while warm. 

Genuine gesso is a hard, chalky surface often consisting of more than 15 thin layers, which is water sensitive and cracks when used on a flexible surface, so it should only be used on rigid substrates to avoid cracking. It is super absorbent. It’s worth noting that the term Gesso is often used for all types of primers and primers because it was the original. Because of this, most people differentiate the ‘warm glue’ type of gesso by calling it ‘true gesso’, ‘genuine gesso’ or ‘traditional gesso’.

Grounds

Choosing from soft to hard, smooth to textured, absorbent to non-absorbent, white or coloured, you can dictate the characteristics of your grounds as this is the surface that your paint will come into contact with. It’s what you paint onto. Many acrylic texture pastes such as fibre paste, modelling paste, or iron oxide can be used as a base for painting. The characteristics of your ground affect the way the paint handles, how easily it moves on the surface and how quickly it dries.