Different types
of paint may be applied to a canvas.
For hundreds of years, artists have been using canvas as a painting surface. Raw canvas is stretched over stretcher bars, then the surface is primed. To prime a canvas, a thick, white acrylic paint (known as primer) is mixed with water and then painted on the canvas. This process actually helps tighten the canvas on the stretchers because the canvas shrinks as it dries. Different types of paint may be applied to your canvas, depending on your tastes and preferences.
Oil
Oil paint is a traditional medium still widely used today. Oil paints are made from pigments suspended in oil. It is well known that oil paint dries very slowly. However, it is less well known that oil paint does not actually dry at all. The process by which oil paint hardens into a state that we call "dry" is actually a chemical reaction. The oil oxidizes slowly and over a long period of time. This oxidization can cause raw canvas to degrade over time. This is why oil paint must be applied to primed canvas.
Acrylic
Acrylic paint is water-based. Acrylics can dry within minutes to form a permanent bond with the canvas. Unlike oil paint, acrylic paint is safe to apply to unprimed, raw canvas. In fact, acrylic paint can be applied to nearly any surface; it sticks to almost everything. However, most artists still used primed canvas for their acrylic paints because raw canvas is absorbent and will absorb expensive paints.
Tempera
Tempera paint is often used as a children's art and craft material, but tempera has a long tradition in art. Tempera paint was commonly used before the popularization of oil paint in the 14th century. Although tempera is not normally applied to canvas, it can be used on canvas, though it may crack or flake when dry. Traditionally, tempera paints are applied to stiff surfaces like wooden panels.
Mixed Media
"Mixed media" is a blanket term used to identify art that has been made with a variety of mediums or materials normally kept separate. Although acrylics and oil paints should not be mixed (they have significantly different drying speeds, which can cause cracking over time), materials such as fabric, paper and even metal can be used on canvas, in addition to acrylics or oils, to create a mixed-media piece.
