Surface Preparation of Canvas
Canvas is available in two forms, gessoed or pre-sized and ungessoed. Pre-sized, usually with gesso (acrylic medium combined with white pigment – very opaque, flexible and non-yellowing) and coated with a layer of white acrylic paint. The second is unsized, or ungessoed, canvas ready for surface preparation. Either you choose is available in many widths and textures. Many artists buy the sized and coated canvas (pre-stretched or by the roll), but then put on additional layers to further seal the fabric weave. Unsized canvas should be primed in all painting applications except acrylic staining, in which the canvas is purposefully left open and absorbent.
There are several techniques for surface preparation when dealing with canvas. If the canvas is already pre-primed with gesso and/or acrylic pigment, additional layers of gesso might be added to create a smoother and more even base upon which to paint. If you prefer an extra smooth finish, apply gesso over the pre-stretched canvas surface, making strokes in one direction. Allow it to dry thoroughly, and then apply a second coat in the opposing direction. If you use a soft brush, smoothing out obvious brush strokes as you apply the gesso, your finished product will be fairly smooth. But, if extra smoothness is desired, sand the surface lightly with light-grit sandpaper to remove any irregularities in the surface; then clean away dust with a soft cloth. If further smoothing is necessary, sand with sandpaper that is even finer.
Extra smooth finishes can be obtained by repeating the steps above. After the third or forth coat, begin to use finer and finer sandpaper, along with water, to polish the surface to a near glass-like finish. It can take up to eight coatings and sandings to achieve the extra-smooth finish loved by many fine detail artists who consider the effort well worth their time.
Raw canvas intended for use with oils should be sized with at least four coats of gesso. For use with acrylics in all techniques but staining, sizing (gesso, etc.) is also necessary. Application of the first layer could be done with a wide putty knife. The blade will smooth the gesso over the surface and work it into the weave of the fabric. Attempt to apply the gesso smoothly with the blade, avoiding ridges and oozes. After this coat dries, sand it lightly with medium sandpaper and clean with a cloth to remove the dust. Repeat the application/sanding process for two additional layers. Clean any dust from the surface and it is ready.
Although there is added effort involved in the preparation of unsized canvas, it is available in weights heavier than pre-stretched/sized canvas. This is especially helpful when the works are large. Thicker canvas stretches tighter for a smoother, more professional presentation and will not relax over time.
A further advantage to sizing your own raw canvas or resurfacing a pre-sized canvas is that you can augment the texture on the surface. If you want to create an impasto look, you can apply gesso thickly and build a surface. With thick, visible texture, less paint yields a richly applied painterly surface. You can also press textures into a thick, wet layer of gesso for unique textures. Some tools that are used for this method of surface preparation include crushed kraft paper to yield a broken, uneven, crackle-type surface; knife blades to create ridges and lines; and sponges to create a uniform but not smooth surface. Adding material such as sand, small stones or gravel, grasses, small twigs and the like to a layer of gesso can create some wildly textured surfaces that are unique.
Consider how fortunate we are to be able to pop into any art supply center and purchase acrylic gesso. The old masters were forced to create their own canvas preparation material. The ordeal began by melting animal hide glue (an organic product that turns rancid easily) and then combining it with powdered white pigment. This concoction was cooked in a double boiler until melted and well blended and then applied to the surface while still hot. It could only be used on wood or other rigid backings, as any flexible surface like canvas would allow the brittle surface to crack or break and fall away.
Hide glue surfaces cannot endure any blows or hard treatment and must be handled carefully. Despite all of these challenges, modern painters have begun a renaissance of this surface treatment method. Technique purists and oil painters that are trying to reproduce the look of old works are especially fond of the surface–purists because it hearkens back to the period of the masters and historical painters because of the “easy to age” surface. Today, paintings can be created that have the look of centuries-old pieces.
So if you paint on canvas (or canvas boards or Masonite), there is a surfacing method that could add new dimension to your work. Perhaps you are ready to add thick textures in the surface preparation. Perhaps you want to paint on an extra smooth, slick surface where every brush mark can be blended to perfection. Or maybe you want to begin to work on a new grand scale and want to know how to surface your own canvas. With today’s materials, there is a preparation method exactly suited to your needs that makes it easier and faster than ever.