Small bubbles in the top paint film, some burst.
Common Cause
It is often seen that more or less moisture goes into the paint film, even in the best refinishing job. When moisture brings enough pressure to paint film, it will lessen adhesion between coats or adhesion of the whole coating to the substrate. Then small bubbles come out. It is often happens in hot, rainy or humid days. (1) Main reason: improper preparation and cleaning of surface. Surface not completely dry after sanding or cleaning with water. Use petrol instead of recommended degreaser to degrease, its content of water soluble or foreign matters remain on the surface.
No enough time for complete evaporation for solvent due to insufficient flash-off between coats or excessive coating thickness of primer.
Use too fast evaporating thinner or high viscosity paints.
Bad quality thinner will make the primer not dry properly. After topcoating, solvent remained in the undercoats evaporates by heat and cause poping.
Insufficient flash-off time before force dry, sudden heating-up, too fast exterior drying.
Too high temperature for drying.
Too high air pressure of spray gun or dry spray method for applying primer.
Repair
Sand and refinish.
Comments