Protecting Acid Stained Floors

Acidic based stains have become a popular floor treatment throughout the decorative concrete industry due to their versatility, ascetics and cost. These stains are comprised of acid, water and metallic salts and come in a range of natural colors, which can be reduced and mixed to create works of art. The downside of these surfaces is that they need to be properly protected or maintained from abrasion, preventing premature failure.

Since the stain only penetrates approximately a 1/32 of an inch into the concrete matrix it is only as strong as the surface. In many cases the very surface of the concrete can be weaker than its mass due to finishing techniques and curing methods. Due to chemical costs contractors seal and protect the surface by applying multiple coats of an acrylic based sealer. This method leaves it up to chance that the property owner will maintain the floor and apply a sacrificial material such as wax. Over the years I have visited numerous projects that have one thing in common, lack of maintenance. The surfaces have become scratched and worn to the point that the stain has begun to walk off leading the way to a headache for the owner and contractor.

There are ways of preventing this situation from happening to you. First, always make sure to remove all of the stain residuals from the floor following the manufactures written directions. Once the surface is dry you should be able to run your hand over it and it should be clean. These residuals will act as a bond breaker and prevent any coating or sealer from properly adhering. Secondly, make sure that the surface is thoroughly dry, excess moisture can not only white out the coating it may also prevent penetration and cause delaminating. How do you know when the surface is really dry? A simple test is to weigh down a 2'-0" x 2'-0" piece of 4 mil plastic for 2-4 hours prior to the sealer application. Observe the plastic for fogging or darkening of the concrete, presume that excess moisture is still present and further drying is required or a moisture problem exists. Some manufactures supply moisture test kits that will determine excess moisture or moisture vapor problems.

When it comes to protecting your work, a two coat application of urethane will achieve the best results. A good quality urethane will cost between 30 to 60 cents a square foot. These products can be rolled, sprayed and even wiped on with a lamb's wool or sheep's skin applicator. Be careful to follow the recoat times specified by the manufacture. Lack of adhesion may result from waiting to long or blistering when reapplying to early. The most popular types are solvent based systems because of their ability to enhance the color of the stains and there rapid strength gain. But of course, in some cases the solvent odor may be an issue, so water based systems should be used. Most quality urethanes are two component systems, make sure that you strictly follow the mixing directions and do not reuse the same mixing container unless all of the dry or wet material has been removed. The final step for a quality finish is to protect it from abuse while it is still curing with caution tape and verbal warnings.