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Origin and Potential Causes:
· Improper surface cleaning or preparation. Moisture left on primer- surfacer will pass through the wet topcoat to cause pin holing.
· Contamination of air lines. Moisture or oil in airlines will enter paint while being applied and cause pinholes when released during the drying stage.
· Wrong gun adjustment or technique. If application is too wet, or if the gun is held too close to the surface, pinholes will occur when the air or excessive solvent is released during dry.
· Wrong thinner or reducer. The use of a solvent that is too fast for shop temperature tends to make the refinisher spray too close to the surface in order to get adequate flow. When the solvent is too slow, it is trapped by subsequent topcoats.
· Improper drying. Fanning a newly applied finish can drive air into the surface or cause a skin to form, both of which result in pin holing when solvents retained in lower layers come to the surface.
· Insufficient sanding or filling of pores in fiberglass substrates.
· Insufficient mixing of polyesters. · Solvent popping that has not been sanded to smooth.
· Insufficient isolation of polyesters.
Prevention Techniques:
· Thoroughly clean all areas to be painted. Be sure surface is completely dry before applying undercoats or topcoats.
· Drain and clean air pressure regulator daily to remove trapped moisture and dirt. Air compressor tank should also be drained daily.
· Use proper gun adjustments, techniques, and air pressure.
· Select the thinner or reducer that is suitable for existing shop conditions. mix polyesters.
· Completely sand smooth solvent pop pores and other defects before refinishing.
Remedy :
After thorough drying of the affected area, sand completely smooth, reapply polyesters or undercoats as necessary and refinish.
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