CSLB C-33 Painting & DecoratingSurface PreparationHard
A painting contractor is preparing to paint a newly installed fiberglass door. The door manufacturer recommends scuff sanding before priming. What is the primary purpose of this scuff sanding?
- ATo etch the surface for better chemical adhesion of the primer.
- BTo remove any mold release agents or surface contaminants.
- CTo create a mechanical profile (tooth) for the primer to adhere to.
- DTo create a smooth, glossy surface for superior paint flow.
Show answer & explanationAnswer & explanation
Correct answer: C. To create a mechanical profile (tooth) for the primer to adhere to.
Fiberglass surfaces are typically very smooth and often have a gel coat, which can be slick. Scuff sanding (light abrasion with fine-grit sandpaper) creates microscopic scratches or a 'tooth' that allows the primer to mechanically grip the surface, improving adhesion.
Why the other options are wrong
- A. Etching typically implies a chemical process; scuff sanding is a mechanical process.
- B. While cleaning removes mold release agents, scuff sanding's primary purpose is not contaminant removal but surface profiling.
- D. Sanding creates a dull, abraded surface, not a glossy one; a glossy surface would hinder adhesion.
Scuff Sanding Fiberglass
Lightly abrading a smooth fiberglass surface with fine-grit sandpaper to create a mechanical profile for improved primer and paint adhesion.
- Essential for smooth, non-porous surfaces.
- Creates 'tooth' for mechanical bonding.
- Prevents paint delamination.
Memory trick: Smooth fiberglass, scuff to stick.