Part 2 in a Series on Coating New Concrete
Last time we discussed the fact that new, or green, concrete must first dry out before an epoxy coating is applied. This drying process typically takes four weeks, but even longer time periods are required in high humidity or under certain sunlight and weather conditions. So what about concrete staining? Can you do that with new concrete?
Concrete color stains come in two types: acid-based and water-based. As you might imagine, acid-based stains are potentially hazardous to the health of our employees and can damage concrete if applied improperly. Therefore, California Custom Coatings does not use acid-based concrete stains. We also do not use solvents when doing concrete staining. Both acids and solvents can damage uncured concrete, and therefore are not recommended for use on green concrete. Water-based concrete stains, like those used by California Custom Coatings, do not use either of these components. Therefore, our water-based stains can be applied to new concrete. There is, however, a catch to applying stain on new concrete.
Compare it to working with watercolor paints. To get a darker color, you use less water. Lighter colors use more water. Now apply this concept to concrete stains. They contain water and pigments, whether they use acid as a component or not. Therefore, if the concrete is evaporating more water into the stain while it dries, the color of the stain changes! And you can imagine that concrete slabs do not evaporate water at the same rate, in the same place, at the same time. As a result, any stain applied to green concrete is likely to experience unintended color effects and have very little uniformity.
Also, as with epoxy coatings, it is not possible to put a protective polymer topcoat on the color stain until the concrete is completely dried out. As with other epoxy coatings, it takes at least 28 days before an impermeable polymer layer should be applied to new concrete. Depending on the circumstances, stains might be applied about two weeks earlier, but any protective coating must wait for complete curing.
Our next article will look at the topic of polishing new concrete.