“Greengrit” (10-20) Pool Filtration crushed glass is made of 100% crushed recycled glass that has been washed, disinfected, dried, screened, and bagged. The coarse, angular material is effective in trapping dirt and impurities in the filter, and offers greater filtration power than sand. Glass grains are less porous. The crushed glass does not saturate itself compared to sand (does not form a cake in the filter).