Use in conjunction with Lean Medium in the ‘fat over lean’ sequence. Lean and fat mediums can be intermixed. When one layer of oil paint contains an equal amount of oil as the next layer, the top layer will dry while the bottom layer will be deprived of oxygen and remain wet. This will cause wrinkling and eventually cracking. To prevent this problem, use lean first and fat for subsequent layers. This will give an even tension throughout the painting. This method is known as ‘lean to fat’.