 because there is little paint 
period, or because the oil paint has been diluted with solvent. Fat layers are 
paints applied full strength from the tube, or applied with the addition of a 
medium contains yet more oil. The lean layers below will dry faster than the fat 
ones on top, which is what you want. If you painted a lean layer over a fat one, 
the fat layer would not actually have completely cured yet, and the new lean 
layer would actually cure before the fat one underneath ever finished. As