The blast media I use is pure glass beads, and has no salt. I add a tablespoon of salt for flavor to a 1 cup plastic/1/2 cup bead mixture. I also add 1/2 teaspoon of heat stabilizer, and 1 teaspoon of softener.
http://www.ebay.com/itm/8-LBS-Glass-Bead-Medium-Grit-MIL-SPEC-8-70-100-grit-Sand-Blasting-Abrasive-/111672165459?hash=item1a002e0453:g:VocAAOxydgZTKU6c