One of the most interesting things you can do with concrete is acid stain it. Specialty concrete contractors have been doing this for many years because it gives a much different aspect to decorative concrete and produces a type of faux stone look.
Some products are called concrete stains that are essentially water-based paints, and though they have their applications, they do not produce the same appearance as the acid stain does. Some people mix in some water based stained areas along with the acid stain ones, especially when applied to an imprinted concrete design.
Concrete is porous, but not the same as wood. A wood stain might create some kind of design in concrete, but it would be hard to control it even if were a product designed for use on cement and it wouldn’t look the same as acid stain.
Composition of the Stain
Acid stain comes in a concentrated bottle that is mixed with water and applied with a pump sprayer. The main ingredient is hydrochloric acid, which reacts with the concrete and produces the scratched look.
Other than the water, acid-soluble metallic salts make up the rest of the ingredients in the stain, and these vary to produce the many different colors. While the stain is burning into the top layer of the concrete, the salts respond to the acid causing the coloring effects.
The etching and blotching of the acid stain color produce a veining and enhancement of the concrete and transform the gray lifeless surface to one that you might see in slate or other rock. The colors achieved are generally deeper with a heavier concentration of acid stain.
When concrete is poured and finished, it has impurities and settlings that come to the surface. This can appear as a white powder or frost. Before applying the acid stain to the concrete, the surface should be cleaned with a pressure washer to remove any of the loose dusting. Some apply a diluted acid to the surface prior to the washing.
New concrete should cure before attempting to stain it. The acid stain manufacturer typically gives a required waiting period before applying the acid stain. Acid stain goes into the concrete, but it is still basically a topical product and has to be protected from traffic. A clear sealer is applied for protection and preventing discoloration due to sunlight exposure.
Another type of acid stain is applied to concrete as soon as it can be walked on after the pour. This works under the premise that the acid stain will penetrate better. It does save the time and trouble of pressure washing. After this stain dries, it has to be coated for protection the same way as the other acid stain.
It’s necessary to reapply the finish as a general maintenance. In high traffic areas such as driveways, it should be reapplied every year, but sidewalks generally can go at least two years in between coatings. Most applications are done by using a pump sprayer with a fan tip.
Not all concrete will accept acid stain due to its history. If the concrete was sealed with a curing compound, it will take almost no stain and the older the concrete is, the less acid stain it will take because of the natural sealants in the air that have settled on it over time.
Acid stain is a great way to finish concrete and it is often done on very smooth finished floors. Sometimes the concrete is etched with a saw at equal distance in both directions to create a tile look before the stain is applied, and the finish is applied several times to create a shiny surface.
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Concrete Coating Specialists – Los Angeles
1178 N. Grove Unit F
Anaheim, CA 90201 US
Fax: (866) 701-4317