AS Mediums are number-coded to make it easy to follow the 'fat over lean' rule which, when applied, avoids wrinkling and cracking of the oil paint surface. To prevent this problem, use AS Artists' Oil Painting Medium No. 1 first and then AS Artists’ Oil Painting Medium No. 2 for subsequent layers. This will give an even tension throughout the painting. AS Painting Medium No. 3 is viscous and 'fatter' for those who like a heavier medium and should be used over the leaner mediums.
