What is a common cause of paint bubbles during application?

A common cause of paint bubbles during application is indeed applying paint over a dirty or moist surface. When the surface is not properly prepared, contaminants such as dirt, grease, or moisture can interfere with the adhesion of the paint. This leads to trapping air or moisture, which ultimately results in the formation of bubbles as the paint dries. Proper surface preparation is crucial for ensuring a smooth and even finish, and it involves cleaning and allowing surfaces to dry adequately before painting.

While the other factors can contribute to issues with paint application, they are not as directly linked to the formation of bubbles. For example, using too many paint layers can lead to sagging or uneven texture, but it does not necessarily cause bubbles in the same way that a dirty or moist surface does. Similarly, while low-quality paint may lead to adhesion issues or poor coverage, it is the surface conditions that are most critical in creating those bubbles. Weather conditions can also affect how paint dries, but again, the immediate cause of bubbles is more closely related to the surface's cleanliness and moisture content at the time of application.