Pool Plaster Hand Disc is the best method for removing stains on pool plaster requires getting in the pool. Not a bad option when it is hot! You will need our pool plaster hand pad. The Most Common Cause of Pool Staining is metal corrosive materials. Unlike other sanding blocks, our diamonds are bonded with NON-CORROSIVE material. Its foam block fits your hand perfectly allowing you to apply pressure as needed. Every plaster swimming pool should have one. It also helps to have a mask to make it easier to see. Pool plaster hand disc stain removal block removes all small topical plaster stains. The product can be used above or below the waterline. Last 3 times longer than Pool Stone with no residuals remaining in the pool. Medium Grit.