paintings are those done on specially prepared wooden surfaces. Before the technique of oil painting was introduced by the Dutch masters of the 15th century, panel paintings was done using tempera, in which powdered colour was mixed with egg yolk. It was applied on a white ground, the colours being built up in layers, with tiny brushstrokes, the details often finished with gold leaf. With the invention of oil painting and its introduction to Italy and other countries of Europe, it became easier to create large works of art. In the 1st century a similar technique was employed in Egypt to paint funerary portraits. Many of these remain in excellent condition. Tempera panels were a common art form in the Byzantine world and are the preferred method for creating icons. Because the method was very meticulous, tempera paintings are often small, and were frequently grouped into a single unit with hinged sections, known as a diptych, triptych or polyptych, depending on its number of parts. Some large altarpiece paintings exist, particularly in Italy where, in the 13th century, Duccio di Buoninsegna, Cimabue and Giotto created the three magnificent Madonnas that now hang in the Uffizi Gallery, but were once housed in the churches of Florence. With the development of oil painting, oil on panel began to replace tempera as a favoured method of enhancing a church. The oil paint lent itself to a richer and deeper quality of colour than tempera, and permitted the painting of textures in ways that were highly realistic. Oil on canvas Oil paint comprises ground pigment mixed with linseed and perhaps other oils. It is a medium which takes a long time to dry, and lends itself to varied methods and styles of application. It can be used on a rigid wooden panel, but because it remains flexible, it can also be applied to a base of canvas made from densely woven linen flax, hence, the linseed oil and the canvas base are both products of the same plant which is harvested in Northern Europe. With canvas spread over a wooden frame as a base, paintings can be made very large and still light in weight, and relatively transportable though liable to damage. In the latter 15th century, oil paintings were generally done in a meticulous manner that simulated the smoothness and luminescent layering of tempera. In the 16th century the handling of the paint