Fritz-Pak 98421 10 oz Plaster Supreme Pool Plaster Admixture. Plaster Supreme is a white, dry powdered admixture packaged in a patented, ready-to-use, water soluble bag. It is intended for use in pool plasters, to create a smooth, easily-spread plaster that reduces water loss and subsequent cracking. Plaster Supreme is a chemically active agent that improves the water retention of cement-based plasters, grouts and mortars. In pool plaster, this reduces water loss from evaporation, thus eliminating the need for constant re-wetting in warm conditions. It also reduces water loss to the concrete shell. This allows for better cement hydration and a more even finish. Plaster Supreme also contains pumping additives that make the plaster more workable and easier to trowel. Unlike clay-based additives, Plaster Supreme will not leave residues that can promote discoloration or increased plaster cracking.