Answer
For bamboo before oil, sand dry with 180 then 220. Use 320 only lightly.
Why it happens
Bamboo is dense and can burnish if sanded too fine before oil, while coarse scratches can show.
Recommended grit
Use 180, then 220 before oiling. Use 320 only for a very light final touch.
Wet or dry
Dry.
Success check
The bamboo feels smooth and accepts oil evenly.
What to do
- Clean the bamboo surface.
- Sand with 180 grit.
- Refine with 220 grit.
- Remove dust before applying oil.
Avoid: Do not over-polish bamboo before oil.