What does "checking" refer to in paint finishes?

"Checking" in paint finishes refers specifically to a series of fine cracks that appear in the surface of the paint. This phenomenon typically occurs when the paint film becomes brittle due to age, environmental factors, or inadequate application techniques. These cracks can compromise both the appearance and protective qualities of the paint, allowing moisture to penetrate and potentially lead to further deterioration of the underlying substrate.

Understanding this term is vital for anyone involved in painting and refinishing, as checking is a sign of failure in the finish that might require repair or repainting to ensure a long-lasting and aesthetically pleasing result. In contrast, the other options describe different issues that can arise in paint finishes, such as thick layers leading to sagging, discoloration which may be caused by UV exposure or chemical reactions, and rough textures often linked to improper application or contamination.