A smoothly troweled concrete Slab needs to be roughed up by either Acid Washing or shot blasting. Acid washing (or etching) involves mopping a dilute solution of muriatic acid over the floor, then rinsing thoroughly. Because the procedure is fairly simple, it’s popular with many contractors. But most coatings specialists advise that abrasion with a shot blaster prepares a slab more thoroughly than acid washing.