Canvas can either be stretched onto wooden stretcher bars or paneled on a flat board, but most artists use the former for their art. Canvas itself is a thick woven cloth made out of cotton, hemp or flax. It is a breathable fabric, which is important when applying paint. However, paint should never touch the bare canvas -- it can deteriorate the fabric over time -- which is why the canvas needs to be primed prior to painting. You can use most paint, either water or oil-based, on a canvas, but certain paints are more commonly used for canvas because of their durability, textures and makeup.
If you are buying a pre-stretched canvas or canvas board, it is most likely already primed, which will be labeled on the package. However, in the cases in which you are using an unprimed canvas, it must be primed in order to paint on the canvas. Gesso is the most common type of primer. It is generally a white paint mixed with a binder that seals the canvas, though it also comes in black, gray and other primary colors. Gesso will make the canvas a bit stiffer and smoother. Liquid gesso is applied with a paintbrush, lightly over the entire surface and sides. Spray gesso is sprayed on the entirety of the canvas. Follow the directions on the container and let the canvas dry for the appropriate amount of time before touching or painting.
Tempera paint, also known as finger paint, is most often used by children for finger-painting or other arts and crafts. It is used by children because it is non-toxic, inexpensive, dries quickly and easy to clean. It is water-based, usually made with pigments and egg yolks or another natural binding agent. The colors are bright and the texture is smooth. Tempera paint can be used on canvas, but if it is too thick, it could potentially crack and peel over time. It is not recommended for serious artists, but for beginners or children.
Acrylic paint is made with pigments mixed with an acrylic polymer emulsion. These paints are water-based, fast-drying and come in a range of quality. Finer acrylic paints are smoother and brighter in color. Acrylic paint is commonly used and recommended for canvas art. It can be easily layered, mixed, thinned with water and texturized. Even though acrylic paints are water-based, they are permanent when dry. The downside of this paint is that if it dries on the paintbrush, it is very difficult to remove. Temperature is another factor that can make working with acrylics difficult, because acrylics can crack in low temperatures. Not only is this paint recommended for beginners, but many revered artists use acrylic paint as well.
Oil paint is made by adding pigments to drying oil, such as linseed. The oil in the paint dries very slowly, and it can take years for the painting to dry completely. Being oil-based, it can be toxic if inhaled or swallowed. The colors are vibrant and the texture is smooth and blend-able. Oil paint is thick on its own and is ideal for applying texture and layers on a painting. You can thin it with turpentine or mineral spirits, though the odor is harsh. Oil paint is long-lasting, but can be expensive. This type of paint is recommended for canvas and is often used by professional painters and artists.