Canvas prints Canada can tell you more on this.
Canvas is normally stretched throughout a wood frame called a stretcher and might be coated with gesso prior to it is to be utilized; this is to prevent oil paint from entering into direct contact with the canvas fibres, which will eventually cause the canvas to decay. A traditional and versatile chalk gesso is made up of lead carbonate and linseed oil, applied over a bunny skin glue ground; a variation using titanium white pigment and calcium carbonate is rather fragile and vulnerable to breaking. As lead-based paint is dangerous, care needs to be taken in using it. Different option and more versatile canvas guides are commercially readily available, the most popular being a synthetic latex paint made up of titanium dioxide and calcium carbonate, bound with a thermo-plastic emulsion. Numerous artists have painted onto unprimed canvas, such as Jackson Pollock,  Kenneth Noland, Francis Bacon, Helen Frankenthaler, Dan Christensen, Larry Zox, Ronnie Landfield, Color Field painters, Lyrical Abstractionists and others.
Early canvas was made of linen, a durable brownish fabric of considerable strength. Linen is particularly ideal for the use of oil paint. In the early 20th century, cotton canvas, frequently described as “cotton duck,” entered usage. Linen is made up of greater quality material, and remains popular with many expert artists, especially those who deal with oil paint. Cotton duck, which extends more totally and has an even, mechanical weave, offers a more economical alternative. The arrival of acrylic paint has actually significantly increased the popularity and use of cotton duck canvas. Linen and cotton stem from two totally different plants, the flax plant and the cotton plant, respectively.
Gessoed canvases on stretchers are likewise available. They are offered in a range of weights: light-weight is about 4 oz (110 g) or 5 oz (140 g); medium-weight is about 7 oz (200 g) or 8 oz (230 g); heavy-weight is about 10 oz (280 g) or 12 oz (340 g). They are prepared with 2 or 3 coats of gesso and are ready for use straight away. Artists preferring higher control of their painting surface area might add a coat or more of their chosen gesso. Expert artists who want to work on canvas may prepare their own canvas in the conventional manner.
Among the most impressive differences between modern-day painting methods and those of the Flemish and Dutch Masters is in the preparation of the canvas. “Modern” strategies take advantage of both the canvas texture along with those of the paint itself. Renaissance masters took extreme measures to ensure that none of the texture of the canvas came through. This needed a painstaking, months-long process of layering the raw canvas with (typically) lead-white paint, then polishing the surface, and then duplicating.  The end product had little resemblance to fabric, but rather had a glossy, enamel-like surface.