What is Cratering?
Painting over porous surfaces can often lead to a number of issues, one being cratering; which occurs when round, concave depressions form during the painting or drying stages. The type of paint used can also lead to increased cratering, also known as foaming. Paints such as lower quality, high gloss paint, or even using a half-empty tin of old paint with excessive rolling or brushing during application can be the cause of the problem.
Although all paints will lead to some form of cratering during application, this can be avoided to an extent by using semigloss paints with shorter rollers, and if cratering persists, sand down the problem area and repaint carefully and slowly to prevent further cratering. During the application and drying process is when most cratering occurs; so be careful to take the time to apply the proper semigloss paint slowly, ensuring that any craters that do form are smoothed out with short rollers.
Make sure that fresh paint is used and application of paint to porous surfaces is taken into consideration, by using rollers and an appropriate sealer or primer first, and then a semigloss paint afterwards.