A
wood stain consists of a colorant suspended or dissolved in an agent or
solvent. The suspension agent can be water, alcohol, petroleum distillate, or the actual finishing agent (
shellac,
lacquer,
varnish,
polyurethane, etc.). Colored or 'stained' finishes, like polyurethane, do not penetrate the pores of the wood to any significant degree and will disappear when the finish itself deteriorates or is removed intentionally.