Term in painting for a support of wood, metal, or other rigid material, as distinct from canvas or other flexible material such as silk. Until the introduction of canvas in the 15th century, nearly all movable paintings in Europe were executed on wood, and it was probably not until the early 17th century that canvas overtook it in popularity. When the word ‘panel’ is used without qualification in describing paintings, it therefore almost invariably implies wood, but many other rigid materials have been used as supports. Painters who worked on a small scale often used copper panels (Elsheimer is a leading example), and in the colonial art of South America copper and tin and even lead and zinc were used. On a larger scale, slate has occasionally been used as a support, notably by Sebastiano del Piombo in several works and by Rubens for his altarpiece for S. Maria in Vallicella (the Chiesa Nuova) in Rome; the picture he originally painted, on canvas (Virgin and Child Adored by St Gregory and Other Saints, 1607, Mus. B.-A., Grenoble), was said to reflect the light unpleasantly and slate was used for the replacement to produce a more matt finish (1608, in situ). In a more experimental vein, Stubbs painted numerous pictures on earthenware panels, using enamel paints, hoping that works produced in this way would retain their freshness and resist cracking better than oil paintings. Technically his results were impressive, but the smooth, glossy finish was not to everyone's taste, and the process was too demanding and expensive to attract imitators. The choice of wood for panels rested mainly on local availability. In Italy, poplar was most commonly used, and oak was preferred in northern Europe. Many other types were used, however, including beech, cedar, chestnut, fir, larch, linden, mahogany, olive, and walnut. Today cedar, teak, and dark walnut are favourites, and modern painters have also used plywood, fibreboard, and other synthetic materials as supports.