Sunday, July 25, 2010

oil painting

Traditional artists' canvas is made from linen, but less expensive cotton fabric has gained popularity. The artist first prepares a wooden frame called a "stretcher" or "strainer". The difference between the first and second is that stretchers are slightly adjustable, while strainers are rigid and lack adjustable corner notches. The canvas is then pulled across the wooden frame and tacked or stapled tightly to the back edge. Then, the artist applies a "size" to isolate the canvas from the acidic qualities of the paint. Traditionally, the canvas was coated with a layer of animal glue (size), (modern painters will use rabbit skin glue) and primed with lead white paint, sometimes with added chalk. Panels were prepared with a gesso, a mixture of glue and chalk.
Modern acrylic "gesso" is made of titanium dioxide with an acrylic binder. It is frequently used on canvas, whereas real gesso is not suitable for that application. The artist might apply several layers of gesso, sanding each smooth after it has dried. Acrylic gesso is very difficult to sand. One manufacturer makes a sandable acrylic gesso, but it is intended for panels only, not canvas. It is possible to tone the gesso to a particular color, but most store-bought gesso is white. The gesso layer will tend to draw the oil paint into the porous surface, depending on the thickness of the gesso layer. Excessive or uneven gesso layers are sometimes visible in the surface of finished paintings as a change in the layer that's not from the paint.
Standard sizes for oil paintings were set in France in the 19th century. The standards were used by most artists, not only the French, as it was - and evidently still is - supported by the main suppliers of artist materials. The main separation from size 0 (toile de 0) to size 120 (toile de 120) is divided in separate runs for figures (figure), landscapes (paysage) and marines (marine) which more or less keep the diagonal. Thus a 0 figure corresponds in height with a paysage 1 and a marine 2 [5].
Although surfaces like linoleum, wooden panel, paper, slate, pressed wood, and cardboard have been used, the most popular surface since the 16th century has been canvas, although many artists used panel through the 17th century and beyond. Panel is more expensive, heavier, harder to transport, and prone to warp or split in poor conditions. For fine detail, however, the absolute solidity of a wooden panel gives an advantage.

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