Sagging is a downward "drooping" movement of the paint film that occurs immediately after application, resulting in an uneven coating.
What Causes It?
Sagging is caused by a number of conditions:
- Applying a heavy coat of paint.
- Applying paint in excessively humid or cool conditions.
- Applying paint that is over-thinned.
- Applying paint by airless spraying with the gun held too close to the substrate that is being painted.
How to Solve It
If paint is still wet, immediately brush out or reroll it to redistribute the excess evenly.
If the paint has dried, sand and reapply a new coat of top-quality paint. Do not thin the paint, and avoid applying paint in cool or humid conditions. Sand any glossy surfaces before application.
Paint should be applied at its recommended spread rate to avoid "heaping on" the paint.
Two coats of paint at the recommended spread rate are better than one heavy coat, which can also lead to sagging. Consider removing doors to paint them horizontally.
Note: Images provided by The Rohm & Hass Paint Quality Institute.