Acid Stain is a coloring process involving a chemical reaction on a cementitious material. A solution made with water, acid and inorganic salts reacts with minerals already present in the concrete, and the result of this reaction is color. It works very well on new or old concrete, and we've seen impressive results over decorative polymer overlays as well as self-leveling products. Acid Stain is a very durable product if properly protected with sealer or wax, and it can be applied to both interiors and exteriors. Acid Stain gives concrete a mottled, variegated, marble like look. It creates beautiful colors on concrete, mostly earth tone browns, reddish browns and greens.