John,
I have one cabinet with glass beads and another with aluminum oxide. In the glass bead unit I have used several different " grits" of beads.
Both cabinets work great on everything I have put in them...nasty rust to light. I wonder if it isn't the media, but the cabinet or air supply or gun.
I feel that sand is a "once through" media and isn't suitable for a blast cabinet, unless you are going to change it often. The coarse glass beads are quite aggressive and will take rust off most anything. If you aren't getting the results you expect, I would look at the system, not the media.
Stuart
