A traditional painting is constructed, in order from bottom to top, of the support, size, ground, paint, and coating. Because all of these layers can affect the appearance of the painting, paintings require special care to keep them looking their best for the longest time possible. Wooden panels are one of the earliest and most common rigid supports for paintings. A variety of trees have been used, mainly dependent upon availability. Other rigid painting supports such as laminated panels and metal have also been used.
Supports made of textiles are, compared to wood, flexible and lightweight.
The fabric is usually linen or cotton. Traditionally, fabric supports are stretched over stretchers and attached at the edges with tacks or staples. Size Untreated supports, flexible and rigid, are usually too absorbent to permit the uniform application of paint. Therefore, intermediate layers, called size and a ground, are first applied. Size is a thin solution, often a dilute glue, that is brushed directly onto the support.