Thursday''s Ask the Experts question from a cleaning professional on the International Custodial Advisors Network (ICAN) "Ask the Experts" page: I have a small area of stamped concrete which has a hazy grey film on it that I cannot remove. I was told that it is minerals from the ground that are seeping up onto the surface. I was told a product called Natural Solution would solve the problem, but Home Depot dropped the product.
Stamped or embossed concrete is an inexpensive and durable surface for use in patios, walkways, and around pools. Since you mention minerals seeping up from the ground, I would surmise that this is an outdoors installation such as mentioned above. You may have to ask a local mason to examine the problem and provide a more accurate solution to the problem than we can from afar. However, we can ask a few questions that may point you in the right direction. For example, is it possible that this film is residue from salt (a no-no on this surface) tossed on it during winter weather? Not cold enough there for that? How about a stain that didn’t take when the concrete was laid? Not likely? Ok, let’s assume that it is minerals leaching from the soil underneath. The site www.concretenetwork.com says pressure washing is “the most effective way to clean concrete without damaging its surface.” Try that simple method first to remove the film. Muriatic (HCl) acid is used to clean masonry, but it reacts... — Lynn E. Krafft, ICAN/ATEX Associate Editor firstname.lastname@example.org