Picture a concrete coloring material that produces a unique look whenever it's applied. No two floors or walls look the same after being treated with this material. That's the magic of the acid-etch chemical staining process--an infinite number of possible results limited only by the creativity of the installer.

Chemical stains can be applied to new or old, plain or colored concrete surfaces. Although they are often called acid stains, acid isn't the ingredient that colors the concrete. Metallic salts in an acidic, water-based solution react with hydrated lime (calcium hydroxide) in hardened concrete to yield insoluble, colored compounds that become a permanent part of the concrete. The variegated and natural look of the end product is its most attractive feature, but this variability can also lead to disagreements among owners, specifiers, and installers. Here are some how-to hints for producing stained surfaces that satisfy customers.