Hi Chris;

What you say makes a lot of sense in that the skin that forms on the surface does keep the cure from progressing deeper at the same rate the top layer did. When I was spraying lacquer, I could swear the drying of the lacquer proceeded faster after I sanded it. As an aside, it took about a year for the lacquer on my 'Vette to thoroughly dry, and I had to sand and buff one last time to restore the surface flatness. The next four years saw no further changes, the sucker must have finally dried & cured!

Tonite I sand my 1st 2 coats, it has about 48 hours drying time. BTW, my reason for wet sanding with #320 was those curious lighter patches that appeared in the polyester resin when doing a dry #180 with the ROS. They disappeared after a finer wet sanding, but not without. That is primarily why I terminated the PR experiment - - Unsure as to what I was seeing.

Nice discussion, Spidey