When does paint usually peel?

Paint typically peels when there is a lack of both a chemical bond and a mechanical bond with the substrate. A proper bond is crucial for the paint to adhere effectively to the surface it is applied to. The chemical bond refers to the interactions at the molecular level that allow the paint to adhere firmly, while the mechanical bond involves the surface texture providing grip for the paint. When either or both of these bonds are compromised, the paint does not adhere properly and can begin to separate from the substrate, leading to peeling.

In contrast, while exposure to sunlight can affect paint longevity and appearance, it is not a direct cause of peeling. Similarly, improper mixing of paint can affect consistency and coverage but is not a primary reason for peeling. Lastly, if paint dries too quickly, it might lead to issues such as cracking or uneven texture, but this is separate from the fundamental adhesion problems that lead to peeling.