The method for preparing a canvas varies from artist to artist. This is
primarily because there are several options to choose from in every
phase of preparation. Here, we outline the choices available so that
you can confidently begin to work in oil.
by Naomi Ekperigin
The method for preparing a canvas varies from artist to artist. This is primarily because there are several options to choose from in every phase of preparation. Here, we outline the choices available so that you can confidently begin to work in oil
|An example of unprimed cotton.
Photo courtesy Fredrix Artist Canvas.
|An example of unprimed linen.
Photo courtesy Fredrix Artist Canvas.
The most common support used by painters, canvas, does not refer to one particular material, but can be used to describe many kinds of closely woven fabric. The two most common canvases used as a support for oil painting are cotton and linen, with linen being the more expensive. When both are unprimed-that is, not coated with a material that prevents the paint from soaking through the surface and deteriorating the canvas-they can be easily distinguished. Both kinds of canvas can be purchased primed or unprimed; either way is acceptable. Both cotton and linen are a light tan color when they are unprimed. Primed canvas allows you to skip the process of mixing and applying the sizing and ground, which many beginning artists and hobbyists prefer. However, unprimed canvas is less expensive, and frequent painters find it beneficial to learn how to apply their own priming,
as it cuts costs and enables them to create a texture specific to their painting needs.
STRETCHING THE CANVAS
Before the canvas is primed, it must be stretched to fit the frame. Attempting to stretch it after it has been primed will result in cracking and flaking of the priming, which creates a rough surface on which to apply oil paint. Primer also makes the canvas rigid and it is unlikely to yield no matter how hard you tug at it. Stretching your own canvas can be difficult at first, but it is more cost-effective than purchasing pre-stretched canvases, which is a consideration for many artists. The following tools are required to stretch a canvas:
- Four stretcher bars (pieces of wood that make up the frame. These can be purchased at any art-supply or hardware store). The most common bars are tongue-and-groove with mitered corners and beveled sides.
- Staple gun and staples (or a hammer and carpet tacks, depending on preference). Coated or iodized metal staples made of copper or brass are best.
- Canvas pliers (to help you maintain a tight grip on the canvas as you attach it to the stretcher bars)
- Scissors, knife, or other sharp blade.
- Right angle (to ensure evenness)
First, join your stretcher bars at the corners, forming a rectangle. You may have to push them by hand to tighten them, or lightly tap them with a hammer (be careful not to dent the wood when you do this). Use the right angle to make sure that all corners are 90 degree angles. Once the stretchers are securely connected and straight, roll your canvas out on a clean surface. Place the frame on top, and use your scissors to cut the canvas to size, making sure to leave at least two to three inches of extra material on all sides so that you can staple the canvas to the frame.
SIZING, GROUND, and PRIMING
Now that the canvas is attached to the frame, it is ready for sizing and ground. These terms can be very confusing, as their meanings overlap and are sometimes used interchangeably. Sizing is applied first, and acts as a sealant and protection for the canvas. For oil painting, a weak solution of animal glue is applied to linen canvases to protect them from the acid in the paints, which can cause the canvas to deteriorate. Ground is applied on top of sizing, providing a uniform color, texture, and level of absorbency, in addition to acting as an additional layer of protection for the canvas. In the case of oil painting, the most common ground is gesso-- a combination of oil with an inert white pigment such as chalk, whiting, or plaster of Paris, and an aqueous binder such as casein or animal glue.
Gesso can be made and purchased in varying levels of consistency-from cream to a paste-depending on the desired texture and level of absorbency. It also comes in different colors, though white is the most common. Water-based gesso was created in the mid-1950s and it is primarily used for painting with acrylics. Making your own gesso requires heating animal glue, such as a calf or rabbitskin, and mixing it with white pigment. The glue must be heated until it is smooth, but not to the boiling point. Perfecting this method requires practice, and with the various types of prepared gesso available for purchase, beginning artists can avoid this step.
|Applying gesso in thin coats ensures an even painting surface.
Photo courtesy Utrecht Art Supplies.
Normally, gesso is applied in two or three thin coats, to create a smooth finish. If a rougher texture is preferred, only one coat may be necessary. “The amount of gesso applied determines the texture of your painting surface,” explains artist Joe Gyurcsak. “If a painter is going to be working in detail, a smoother surface may be better.”
After stirring your gesso, add a small amount of water (no more than 1 part water to 2 parts gesso) to thin it. It is tempting to mix a lot of water into the gesso to increase its quantity and save money, but doing so creates an unstable ground. “Overthinning is dangerous,” warns Gyurscak. “The polymer can only be broken down so much, and adding water compromises the integrity of the gesso film.” Gesso dries rapidly, so it must be quickly applied in smooth, even strokes in one direction. After the first coat, allow the gesso to dry (approximately one hour) and lightly brush with fine sandpaper to smooth. After smoothing, wipe the surface with a soft, dry cloth to remove dust and residue.You should also thoroughly rinse your brush between applications, because gesso cannot be removed once it dries. The next coat should be applied in even strokes in the opposite direction of the previous coat so that no brush marks are visible. Don't forget to coat the sides and corners of your canvas-many paintings have disintegrated along the edges due to lack of priming.
For more application tips, view Utrecht's canvas prep page.
Naomi Ekperigin is the editorial assistant for American Artist.