Acid staining is accomplished by applying a chemically reactive, acid-based solution to cured concrete. The translucent, mottled, and variegated coloring effects achieved with acid stain are unique to each individual surface. This is because unlike paint or acrylic stain, acid stain is not a coating and contains no pigment. A chemical reaction occurs between the compounds in the stain solution and the minerals present in hardened concrete. This reaction actually turns the concrete a different color. Diverse concrete mixes and finishing techniques ensure that each concrete surface will take the stain differently. Therefore, color charts can give only a general indication of the stain’s final color and appearance.
Commercially blended acid stains come in about 10 colors, primarily earth tones. A single color can be used, or for more striking effects scoring and multiple colors may be applied.
If acid stain cannot be readily absorbed into a concrete surface, it cannot react with the minerals therein. For this reason, anything that impedes liquid absorption must be removed from the concrete. This includes concrete sealer, carpet or tile glue, pvc glue, wax, acrylic floor finish, paint, varnish, etc. Only after such substances are completely removed may staining proceed.
When the concrete is thoroughly clean, the acid stain solution can be applied. This is commonly done with an all plastic, pump-up garden sprayer. The stain is allowed time to react with the concrete. When the reaction is complete, the residue created by the reaction is thoroughly cleaned off and the surface is neutralized. After the concrete has dried thoroughly, concrete sealer is applied. This not only protects the surface from wear, but also greatly enhances the stain color.