Answer
For a bicycle frame, scuff old paint with 220 or 320, then refine with 400 or 600.
Why it happens
Old paint, bare metal, and primer areas need a clean scuffed surface before repainting.
Recommended grit
Use 220 or 320 for old paint scuffing, then 400 or 600 before primer or topcoat.
Wet or dry
Dry for shaping; wet for finer finishing stages.
Success check
The frame is clean, dull, and evenly prepared for coating.
What to do
- Clean the frame thoroughly.
- Scuff old paint with 220 or 320.
- Use 400 or 600 for finer paint prep.
- Remove all dust before primer or paint.
Avoid: Do not leave glossy old paint under new paint.