page_title: Canvas
section_title: As a compound agent
hierarchical_section_title: Canvas / As a compound agent
caption_attribution_description: Post Offices in or around London Ontario
context_page_description: Canvas is an extremely durable plain-woven fabric used for making sails, tents, marquees, backpacks, shelters, and other items for which sturdiness is required, as well as in such fashion objects as handbags, electronic device cases, and shoes. It is also popularly used by artists as a painting surface, typically stretched across a wooden frame.
  Modern canvas is usually made of cotton or linen, along with polyvinyl chloride, although historically it was made from hemp. It differs from other heavy cotton fabrics, such as denim, in being plain weave rather than twill weave. Canvas comes in two basic types: plain and duck. The threads in duck canvas are more tightly woven. The term duck comes from the Dutch word for cloth, doek. In the United States, canvas is classified in two ways: by weight and by a graded number system. The numbers run in reverse of the weight so a number 10 canvas is lighter than number 4. Canvas has become the most common support medium for oil painting, replacing wooden panels. It was used from the 14th century in Italy, but only rarely. One of the earliest surviving oils on canvas is a French Madonna with angels from around 1410 in the Gemäldegalerie, Berlin.
context_section_description: From the 13th century onward, canvas was used as a covering layer on Pavise shields. The canvas was applied to the wooden surface of the Pavise, covered with multiple layers of gesso and often richly painted in tempera technique. Finally, the surface was sealed with a transparent varnish. While the gessoed canvas was a perfect painting surface, the primary purpose of the canvas application may have been the strengthening of the wooden shield corpus in a manner similar to modern glass-reinforced plastic.
caption: Canada Post canvas bags
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