What causes runs or sags in paint?

• A. Not applying enough paint
• B. Using wrong solvent
• C. Painting in cold temperature
• D. Applying too much paint too quickly

Answer: (D)

Runs or sags come from laying down a wet film that’s too thick or applying it too quickly for it to level and set before gravity pulls the excess downward. When a single pass or coat is too heavy, the solvent-rich layer stays soft longer, and the weight of the wet film causes it to flow downward, creating a sag or drip. The fix is to use thin, even coats and allow enough flash-off time between passes so the film can level out and dry properly. Not getting enough paint on, or changes in temperature or solvent can affect drying, but the direct cause of a sag is the excessive, rapid application of paint.