Fat-Over-Lean is a technique used in oil painting to ensure that the painting does not crack and maintains a strong film strength. Fat paint contains a higher ratio of oil to pigment (or other additives like chalk). Lean paint is applied in lower layers of the painting, and fatter paint is applied on top of it. Fatter paint tends to dry slower than lean paint, and is usually more flexible. Cracking or crazing can occur when the top layers of paint dry quicker then lower layers. This causes top layer to shrink, while the lower layer doesn’t.
