Priming a canvas is necessary before beginning the painting process.
Store-bought canvases are typically sold stretched, "sized" and primed and ready for an artist to use. Sizing is a thin substance that creates a separate membrane to keep oils in the paint from entering the canvas fibers; without sizing, the oils would cause rot. Priming creates the surface for the paint and can have different degrees of absorbency, which will affect applied paints' drying time and the overall appearance of the painting. Follow the steps outlined below if your store-bought canvas has not been sized and primed, or to add additional layers of priming for a smoother, more absorbent painting surface.
Instructions
Sizing
1. Combine 1 tbsp. of rabbit skin glue crystals with enough water to cover in a glass jar. Wait until the contents have doubled in volume, about 20 minutes.
2. Fill the jar three-quarters full with cold water and place on top of the jar lid in a saucepan containing warm water. Place the saucepan on stove or hot plate and let crystals dissolve over low, gentle heat for approximately 30 minutes.
3. Remove the jar and saucepan from the heat and allow the sizing to cool until it has the consistency of jelly. If the contents are too solid, reheat and add more water, then allow sizing to set again.
4. Return the jar of sizing to the saucepan filled with water and reheat until once again dissolved. Apply the sizing to the canvas using a bristle brush, working from the edge in one direction only. Cover the entire surface of the canvas uniformly, then allow it to dry flat for several hours.
5. Apply a second coat of sizing in the opposite direction to the first and allow the canvas to dry completely before proceeding.
Priming
6. Reheat the sizing in a water-filled saucepan over low-heat. Add gesso powder to the sizing and mix until the consistency is that of thick cream.
7. Apply the gesso primer to the canvas using your bristle brush. Cover the surface of the canvas entirely in a smooth, even layer of primer.
8. Lay canvas flat to dry. Apply additional coats of primer to the canvas depending on your desired smoothness and absorbency. The more coats applied, the more absorbent the surface will become.
9. Sand the surface of the dried canvas lightly with sandpaper to smooth out any bumps and brush strokes in the priming.
