Panel, in art, refers to any rigid surface that can be used to paint on it. The surface can be wood, stone, copper, or any other surface on which we can apply paint. Wooden panels were common in the early ages. These paintings date back to the 11th century and are seen in American, European, and Russian museums. Panel paintings were commonly used in altarpieces. Panels were used as a surface for painting until the canvas became popular in the 16th century.  Artists had to do prepare the wooden surface to use it as a panel. First the wood was seasoned, then sanded and planed, after which a layer of ‘size’ and multiple layers of gesso was applied to harden the surface. On this rigid surface the artists first creates an outline using charcoal and then applies paint.