: Why is it that 120 grit sand paper takes off 10 times more gel coat
: than 150, 100, 80, and 60?

: Not saying this is scientific but I switched today and did more in
: an hour than several hours experimenting with others. The 120
: and a hook and loop soft pad about 3/4" thick is the bomb

Thank you, you have confirmed that I'm not crazy. I have found the same thing, and I believe that it may in part be due to the hardness of the abrasive material, and perhaps the number of grains per inch actually doing the removal. Sure with 80 grit you have bigger grit, but it also has less grit per inch. 120 has more grit per inch so it's going to have more "little scratchy things" doing the work. That would explain up to 120, but then 150 should be better, right? So that's why I say maybe the actual abrasive is part of the reason. The abrasive itself may be harder even though it's cut finer.

That's just theory, but I have thought about this myself. I spend all this time with 80 grit thinking I'm going to cut faster and I go to 120 and it plows through it. I'll say this- I have found the same situation with Japanese water stones. As soon as I get down to the 8000 grit it leaves a big black streak on the stone the first pass. It seems to cut much faster on the 8000 than on the coarser stones.

Anyone else? This is theory.