Answer
For drywall tape edges, use 150 or 180 on ridges, then 220 for final feathering.
Why it happens
Compound over tape needs feathering without cutting into the tape or paper.
Recommended grit
Use 150 or 180 for high ridges, then 220 for final feathering.
Wet or dry
Dry.
Success check
The tape edge is feathered and blends into the wall.
What to do
- Let joint compound dry fully.
- Level high ridges with 150 or 180.
- Feather edges with 220.
- Remove dust before primer.
Avoid: Do not sand through the tape surface.