Sagging or Running
This paint failure is easily identified as paint film with a droopy, dripping appearance.
o Application of a coat of paint was too heavy or overloaded.
o Paint was thinned too much at the time of application.
o The paint was applied in poor environmental conditions, such as when temperatures were too cool or when humidity was too high.
o The paint was applied to a high-gloss surface that was not first primed. This prevents the paint substrate from having the "tooth" necessary for the finish coat to adhere.
o Painted surface was not clean or properly prepared at the time of application.
Repair and Prevention
o If you catch the sagging while the paint is still wet, use a brush or roller to redistribute the excessive paint evenly.
o If the paint is dried, sand the uneven area and lightly reapply paint.
o If the paint was applied to a glossy surface, sand the glossy surface to dull it and create a "tooth" for the paint to adhere, or apply a primer and repaint.
o Paint using two light coats instead of one very heavy coat.
o Do not overload the paintbrush. Follow proper technique for use of a paintbrush.