MATERIALS AND TECHNIQUE (Oil Painting)

Most artists today use commercial materials but some prefer to make their own paints in the traditional way. Oil paint consists of pigment ground in oil that dries on exposure to air. The pigments, or colored powders, must be lightproof, insoluble, and chemically inert. The oil is usually linseed but may be poppy or walnut. Sometimes varnish is added to the mixture, which is then ground. The stiff, creamy paste that results is packaged in flexible tubes. The painting surface consists of a support, either a wood or composition panel, or more frequently, linen, cotton, or jute canvas stretched on a frame or glued to a board. The support is covered with a ground, a thin coating of gesso or other gypsum and glue, or size. The ground makes the support less absorbant and provides an even painting surface that is neither too rough nor too smooth. The ground may be white but is often given a toning coat of gray, tan, or pink. Traditionally, oil painting proceeds in stages. First the design may be sketched on the ground in pencil, charcoal, or paint diluted with turpentine. Then broad areas of color are filled in with thin paint. They are successively refined and corrected in thicker paint to which oil and varnish are added. The paint is usually applied with brushes made from stiff hog bristle, although softer brushes of badger or sable hair may be used. Paint may also be applied with a flexible, wide-bladed painting or palette knife, or the fingers. The process may require only a few sessions or extend over months or even years. Once the painting has dried, at least a year after completion it is varnished to protect it from dirt and to enrich the color. Because all varnishes eventually darken, the varnish used should be removable and eventually replaced.