Checking and craking in coating paints

Checking is a model of breaks in the top layer of a coating. Cracking and flaking are higher stages of checking. Checking results when a coating begins to lose its elasticity, developing small narrow breaks due to expansion and contraction. These break is on the surface and do not penetrate to the substrate. They frequently follow the pattern of the grain. Further exposure will result in wider break or cracks in the coating that eventually reach the substrate. As time goes on, the coating begins to flake off.