Introducing HD24 Pre Grind by Surface Gel Tek. This product is used for etching off the initial layers of the top laitance. The product generates no silica dust or noise pollution, contains no VOCs, neutralizes with water and is flushable to sewers. Available in 1 and 5 gal. containers with 300-350 sq. ft. coverage per gallon on smooth surfaces, the HD 24 is 24% acid for heavy etching and cleaning.