What is the chemical resistance of wood?

How do you prepare a wood panel for oil painting? I build my painting surfaces instead of using canvas because I like the resistance that wood gives as a surface. Sometimes I gesso them and other times I seal them with a wood sealer.

• Answer:

  Either gesso or sealer are good options. Basically, it's necessary to prime the wood before painting on it to prevent the oils from the paint from soaking into the wood and rotting or warping it, or leaving the paint dry and cracking on the surface. Painting on unprimed canvas can result in similar problems. Personally, I prefer a primed gesso surface to paint on, sometimes pre-tinted with a pigment or even textured with sand or ground pumice.