Problem Solving Forum
May 18 - May 22, 2020
How can you determine if a concrete substrate is in suitable condition for application of an acid stain?
David Barreto of epmar on
May 18, 2020:
Acid stains are dependent upon the calcium hydroxi ...read more Acid stains are dependent upon the calcium hydroxide or the "paste" portion of the surface to produce the etching reaction that permanently embeds the desired color within the substrate. I generally recommend 2 basic initial tests that anyone can perform. #1,Visual: As we mentioned, "paste" needs to be visible as the more aggregate exposure you see the less paste is present. This basically equates to less color left behind. Acid stains do not typically react with aggregate. Surface contamination such as oil and grease, gum and other foreign matter will prevent acid stains from coming in direct contact with the cement paste, thus leaving a "splotchy" appearance behind. #2,Water test: Simply pour or spray water over the concrete and look for penetration or darkening of the surface. If the water beads and does not begin to penetrate within 20 seconds, then there is a clear protective coating/additive on the surface that would prevent the acid stain reaction. The surface may also be finish-troweled tightly, which will also prevent adequate penetration. If your surfaces do not pass the initial tests I have suggested, please contact an experienced decorative concrete entity for further assistance. They can provide you with options to overcome the flooring challenges to get you the acid stained floor you desire.