Size a Canvas Painting
To size a canvas is to apply gesso or animal glue to an artist's canvas, thus protecting it from the natural acids in oil paints that would deteriorate the canvas over time. Many artists today refer to sizing as priming the canvas. Gesso is the most common modern primer, although animal glue is still used. Even canvases not used for oil paintings are primed. Gesso gives the canvas a smooth and uniform appearance. It tightens the canvas over the stretcher bars, making the canvas a more appropriate painting surface, and it prevents the canvas from absorbing too much of the expensive paints artists use.
Instructions
1. Lay down your tarps and place the unprimed canvas on top. This may be done on the floor or on a table, if the canvas is small enough.
2. In a bucket, mix 4 or 5 parts gesso with 1 part water. Use a paint mixer, a palette knife or a paintbrush to do the mixing. Clean the gesso off your tools immediately after you have finished using them.
3. Dip your paintbrush in the acrylic mixture and paint a single coat of gesso over the canvas.
4. Paint a second layer of gesso over the first layer. You may wish to give the gesso time to dry between layers, but gesso dries so quickly, it likely won't be necessary.
5. After the second layer of gesso has dried completely, sand it down with fine sand paper. This step is optional but will make your canvas a smooth painting surface.
