With new drywall, can I just wait until the third coat to sand any pock marks/fish eyes that may appear? Should I do it after the second coat instead since I am switching to a final coat? (Won't they just fill with succeeding coats?)
Also, is there a bonding purpose to sanding in between coats? I'm unclear whether it is necessary in general to sand after every coat. I'm using a 20k lumen light but its 5000k daylight and it misses things a good old fashioned halogen yellow doesn't.
Best Answer
The purpose of sanding (or scraping) between coats is to knock off the high points. NOT bonding.
Mud (compound) fills the low points, but it shrinks, requiring multiple coats.
The goal is to have something close to a flat surface, which you get most easily by removing the high points and filling the low points.
If you don't remove the high points, you end up filling a larger area with more mud since the knife rides on the high points. More mud shrinks more, so there's more remaining low spot to fill with the next coat. If you knock off the high points, you are just filling the low points, and the amount you add each coat is less, so it shrinks less.