Acid Staining gives floors an amazing, rich, bold look, turning ordinary concrete into an upscale surface that mimics marble, glazed stone, tanned leather, or stained wood. Each concrete slab accepts the stain in varying degrees of intensity creating stunning, multi colored variations in the surface.
Because acid stain is translucent, it plays on the whorls and natural variants in the concrete to create surprisingly beautiful patterns. Once sealed, the colors take on a luminescence that gives the surface a stunning glow. Acid stain is available in an array of earth tones that range from browns, bronze tones, tans, and terra cotta reds to some soft blues and greens.
Acid stains are made up of water, hydrochloric acid, and acid-soluble metallic salts. The stain penetrates the surface of the concrete and reacts with the calcium hydroxide therein. The acidic component of the stain etches the surface, allowing the metallic salts to soak into the concrete. The chemical reaction makes the stain a permanent part of the concrete so it will never fade, chip off, or peel away.
Know Your Slab
The condition and age of your concrete are crucial for successful acid staining. If the surface is too smooth, the stain won’t be able to properly penetrate and will end up being wiped away. Machine troweled concrete will require extra preparation to ensure a consistent stain reaction. The concrete must also be free of contaminants, debris, dirt, oil, paint, adhesives, sealers, etc. Any of these will negatively affect the reaction of your stain. Acid stain will not stain aggregate, rocks, or sand, so exposed aggregate or depleted concrete may cause the stain to take inconsistently or react weakly.
Preparation and Process
Pre-application testing is critical to know how your slab is going to accept the stain and how it will react. Semi-transparent stains will not hide blemishes and will come out very differently on different types of surfaces. Lighting also plays a big factor in how your color will appear. When you’re selecting your colors, be sure to take all of these variables into consideration. It’s also important to remember that the sealing step brings out the colors, sometimes in dramatic ways.
Cleaning is one of the most important steps in acid staining. Concrete floors can have an astonishing number of unexpected contaminants. Depending on the degree of soil, sanding, or stripping might be required before stain can be applied.
Once the floor is properly prepped and cleaned, the acid can be sprayed in a number of ways depending on your desired effect such as marbling vs mottling.
You have a choice of sheen for the sealer on an indoor floor. High gloss sealers create more of a mirror-like finish but may show dirt more readily than a satin finish. Acrylic sealers require a concrete wax for maintenance.