Application Techniques and Coating Defect Prevention
Application Techniques and Coating Defect Prevention tests whether you can build the specified film without runs, texture, or trapped solvent. Most defects are caused by technique, film build, flash time, or contamination, not by a single bad product.
Core rules
- Follow the product's wet film build and coat count. Too heavy a coat causes runs, sags, solvent pop, and die-back.
- Allow the specified flash time between coats. Trapped solvent from too-fast recoating can pop or boil during bake.
- Use the correct gun distance and overlap. Dry spray comes from too much distance, too much air, or too fast a pass; orange peel from poor atomization, too little flow, or too fast a thinner.
- Keep the booth clean. Fish-eyes indicate silicone or oil contamination; do not add fish-eye remover as a substitute for cleaning.
- Control booth temperature and air movement. High heat or direct air can skin over the film and trap solvent.
- Sand defects only after the coating has cured enough; featheredge and recoat within the window.
Worked example
A clearcoat shows small pinholes after bake. The technician had applied three heavy coats with a five-minute flash at 90 F. The likely cause is solvent pop from trapped solvent and too-heavy film. Correction: strip or sand down, then apply thinner coats with the specified flash and bake schedule. Reason: the surface skinned before solvent escaped.
Traps
Adding reducer to fix orange peel without checking atomization, over-thinning, recoating outside the window, and sanding before cure. Also watch for contamination from rags or hands.