Canvas

Canvas is an extremely durable plain-woven fabric used for making sails, tents, marquees, backpacks, shelters, as a support for oil painting and for other items for which sturdiness is required, as well as in such fashion objects as handbags, electronic device cases, and shoes.

In the United States, canvas is classified in two ways: by weight (ounces per square yard) and by a graded number system.

Its use in Saint George and the Dragon by Paolo Uccello in about 1470,[4] and Sandro Botticelli's Birth of Venus in the 1480s was still unusual for the period.

[5] Another common category of paintings on lighter cloth such as linen was in distemper or glue, often used for banners to be carried in procession.

This is a less durable medium, and surviving examples such as Dirk Bouts' Entombment, in distemper on linen (1450s, National Gallery) are rare, and often rather faded in appearance.

Various alternative and more flexible canvas primers are commercially available, the most popular being a synthetic latex paint composed of titanium dioxide and calcium carbonate, bound with a thermo-plastic emulsion.

Many artists have painted onto unprimed canvas, such as Jackson Pollock,[6] Kenneth Noland, Francis Bacon, Helen Frankenthaler, Dan Christensen, Larry Zox, Ronnie Landfield, Color Field painters, Lyrical Abstractionists and others.

Linen is composed of higher quality material, and remains popular with many professional artists, especially those who work with oil paint.

One of the most outstanding differences between modern painting techniques and those of the Flemish and Dutch Masters is in the preparation of the canvas.

This required a painstaking, months-long process of layering the raw canvas with (usually) lead-white paint, then polishing the surface, and then repeating.

The canvas was applied to the wooden surface of the pavise, covered with multiple layers of gesso and often richly painted in tempera technique.

Stapled canvases stay stretched tighter over a longer period of time, but are more difficult to re-stretch when the need arises.

[15] There is an inherent anisotropy to the elastic modulus measured in the weft and warp direction as evidenced in the strain vs. load behavior of the canvas.

[15] Though, tensile testing provides an explicit measure of material strength, conservators are unable to tare a piece of painting to create the samples (required length of 250 mm), therefore the traditional methods of assessing mechanical properties have been visual cues and pH values.

[16] Art conservators have recently adopted a new method called zero-span strength analysis, nanoindentation, and numerical modelling to quantitatively evaluate the mechanical properties of painting canvases.

[16] Another method for assessing canvas quality is nanoindentation utilizing a millimeter-sized cantilever with a microsphere at its end and measuring local viscoelastic properties.

Lastly, conservators are using finite element modeling (FEM) and extended-FEM (XFEM) on canvases undergoing desiccation (removal of moisture) to visualize the global and local stresses.