QuikSand blocks you are talking about? That's what Woodworker's Supply sells. If that is what you are using, be sure to use respiratory protection as with any silica product...also with sanding wood...if you do a lot it will catch up with you one day. I had a person recommend mixing pumice with plaster of paris and letting it set up on a molding to get the correct profile for making a shaped sanding block. Never tried it myself but now you have me thinking about this, maybe I'll try it. Luck, Kizmet