Well, for sure, those are coarse grit sanding marks. Being able to see is crucial to making sure you get all the scratches out from the grit before stepping up to the next grit. This means good glasses, and good light. I don't really like most LED lights because they are too white, and prefer the natural light spectrums, which are generally the florescent bulbs. I never blow off my bowls as I sand. Main reason is that it puts much more dust into the air in the shop, and to me that is a huge problem. I do wipe between each grit, and wipe by hand. In the coarser grits, you still can't see much, but in the finer grits, for me, it pushes the dust into the cracks and high lights them. If I start with 80 grit, the next grit is 100, then 120, then 150, then 180, 220, 320, and 400. The 80 grit scratches are some times more difficult to remove than tool marks, and stepping up from 80 to 120 takes about the same amount of time as 80, 100, then 120. I try to get contrasting scratch patterns. Not sure if you used the inertial sander for those scratches or not. My scratch patterns are more circular with the angle drills. With my angle drills, I use one edge of the pad for one grit, and the other edge for the next one, so I get 2 different scratch patterns. Slow speed makes for more efficient cutting. If you are going too fast, then the abrasives don't get a chance to dig in and cut, where with slower speeds, you get better traction. Maybe as high as 500 rpm for hand sanding, and as slow as my lathe will go for power sanding. Drill speed is never more than half the trigger pull. As some one on another forum said, "Never take a finished piece from the shop into the house on a sunny day. Sunlight causes scratches." I did make an articulated arm for when I sand, and that is a video I have up. This essentially holds my arm as I sand so there is no weight to support. Main thing this does, other than prevent fatigue, is to let me spin the bowl by hand. Huge advantage is making sure you get every thing sanded out before stepping up to the next grit. I spend more time with the first grit or two than I do with the rest of the finer grits. Once you get to 220 or so, you are doing more of a polishing out the scratches than you are sanding out the scratches... If that makes any sense. I did make a sanding hood, and have one up about sanding in general.
robo hippy