Acid Staining Concrete

Many people would look at span of drab grey concrete and see, well, a span of drab grey concrete. It should however, be seen as an opportunity. Decorative techniques in masonry have advanced considerably and that concrete floor (or wall, or countertop) is a blank canvas. One technique gaining popularity is concrete staining.

  There are two types of concrete stain: non-reactive and reactive. A non-reactive stain is a water-based acrylic stain that when applied, is absorbed into the surface pores of the concrete resulting in a opaque uniform color. A reactive stain (also called a chemical or acid stain) is a stain that once applied, has a chemical reaction with the concrete itself resulting in a very unique finish. The results can look like natural stone, polished marble, tanned leather, or even stained wood, depending on the color and technique used to apply it.

  So how does an acid stain work? There are three ingredients in an acid stain: water, metallic salts, and muriatic acid. When the stain is applied to a cement surface, the acid “eats into” or penetrates the surface and allows the the salts to react with the lime deposits (calcium hydroxide) in the cement. This reaction is fueled by the water and results in the creation of colored compounds which are deposited deep in the cement. This creates a distinct pattern of color often described as “marbleized,” “mottled,” or “variegated.” 

 What does it look like? The color compounds are actually contained in the metallic salts which means they come in natural earth-tones. You can choose from shades of black, brown, green, orange, and copper.  The stain will produce a beautiful translucent color and highlight the natural variations in the concrete.  Factors like composition of the concrete, age, texture, and environmental conditions can all effect the final pattern. While a professional can make an educated guess as to the level of coloration (based on experience or an on-site sample), even they can be pleasantly surprised at the dramatic outcome.

 Are there any potential challenges? It should be noted that while stains highlight the natural variations found in the cement, they can also expose imperfections or blemishes.  Like wood, concrete is porous and is excellent medium for staining, but if the canvas is marred by any type of dirt, glue, coating, or sealer, the stain will not fully penetrate.  A qualified professional can determine if and where any problem areas exist and whether or not they can be remedied.  Some may simply add to the character of your finish.

 Use a professional. You should also be aware that while acid staining will never crack or peel, this means the finish is very permanent. Choose your color carefully and approve an on-site mock-up. Understand both the benefits and limitations of acid staining. Due to the complex nature of this type of project you should work with a professional concrete contractor to guarantee a successful outcome.

 With the unlimited design potential of stained concrete you can transform a dull grey concrete surface into a work of art. Acid staining produces a dramatic permanent finish while maintaining the integrity and durability associated with concrete. It is an ideal finish for anyone looking for something truly unique.

About the author

Helen Walker. www.ConcreteIdeas.com is the #1 concrete resource directory on the internet for homeowners, contractors, and suppliers.

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