Answer
Go back to 220 or 240 first, then use 320 after the deeper lines are gone.
Why it happens
The jump from 180 to 320 can be too large when the 180-grit scratches are still deep.
Recommended grit
Use 220 or 240 before returning to 320.
Wet or dry
Dry for normal prep work.
Success check
No visible 180-grit lines remain before the 320-grit step.
What to do
- Return to 220 or 240 grit.
- Use light, even pressure.
- Clean the dust before switching grits.
- Use 320 only after the deeper lines are gone.
Avoid: Do not press harder with 320 grit to force removal.