In order to protect this important and essential art material, as well as your finished paintings, read on. Canvas is a very strong material. Usually made of all cotton, cotton and linen, or linen, it can be woven in any texture from smooth to nubby. Newer synthetic fibers have been introduced as well, and these add strength of a different sort to the basic natural fiber content.
Synthetic fibers resist rot and decay far more readily than natural cotton or linen.
Artists who have developed their own formula for underpainting ground or who do not want the surface sealed use the unprimed surface. Many acrylic painters love the near watercolor effects of using unprimed canvas. Both primed and unprimed canvas should be stored away from strong direct light or exposure to moisture. Light will destroy canvas just as it does any form of fabric. Primed is slightly less susceptible to light damage, but UV contact should be limited whenever possible, whether primed or unprimed.