Originally Posted by
RezDog
It looks like a good time to go up. I used to never drop below 400, because the low grit scratched go so deep. However in more recent restoration I have take a few very aggressively down with low grit, and I feel that those ones had less distortion. Also those black spots are oxidization also. If you can get enough elbow grease on them the do work out with WD-40 and steel wool, and then they leave little pits. It is so,times referred to as devils spit. Sometimes it runs crazy deep. There is no telling where it goes under the surface. Be sure to use a good backer on your sand paper and be mindful not to remove the line and definitions while sanding. The backer will reduce distortion, along with long strokes. I find a cork cut lengthwise as a backer helps me get that edge along the spine and blade intersection.