Decorative Concrete Institute
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ENHANCING CONCRETE with acid staining creates a unique and individual look. Acid stains react differently with every concrete surface and add permanent color to existing concrete substrates.
other system for coloring concrete floors is as wonderfully unique as
acid staining. It never looks the same, and this unpredictability is its
beauty. Once you learn to anticipate the variables, you can be extremely
creative with designs, patterns, and looks. With acid stains, hardscapes
and features can take on an aged patina. When used in conjunction with
decorative saw-cutting, grouting, imprinting tools, and embossing skins,
acid stains make concrete surfaces look like brick, slate, stone, tile,
laying out a pattern, test the substrate. If the surface is contaminated,
clean it thoroughly before applying any stain. The cleaning method depends
on how soiled the surface is. Remove all coatings, paints, waxes, water
repellents, previously applied adhesives, and curing membranes. Then check
for absorbency. In most cases, if the substrate darkens and absorbs the
water, you have a substrate that will accept the stain. If the water beads
up, some type of coating is present.
Coverage and application
rates on acid stained projects vary from substrate to substrate, sometimes
dramatically. Indeed, no load of concrete is the same. You can pour four
truckloads the same day and find subtle variances that contribute to differences
in the way the stain reacts.
The concrete's finish also influences stain coverage -- tightly troweled
concrete absorbs stain differently from broom-finished surfaces. The concrete's
age and chemical makeup also impact the way it receives the stain. In
general, expect coverage of about 150 to 200 sf per coat per gallon of
These techniques are time-consuming and not cost-effective for large areas. Recommended for experienced contractors accustomed to working with unpredictable techniques, these methods require detailed work on your hands and knees and work best in contained spaces.
No matter what application method you use, keep in mind that you're working with a reactive stain. If the tip of your sprayer clogs and spews out drips, the drips can become a permanent feature of your floor; so always protect the areas around your work surface and keep all your tools clean.
Cleaning and neutralizing the stained residue remains the most important step to finishing an acid stained surface. Many contractors clean and seal a surface only to come back and find that the sealer has failed. Using the white cloth test prevents this costly mistake. Simply dampen a clean white cotton cloth with water and run it across the cleaned surface. If the rag soils, the surface is not free of residue. Clean it again, and repeat the white cloth test.
floors with saw cuts and stains look better with grouted saw cuts. First,
apply at least two coats of sealer and allow them to dry overnight before
grouting. When you seal first, then grout, the sealer acts as a resist
and prevents the grout from marring the floor design. After the grout
sufficiently cures, use burlap, denim, or a buffer to remove the excess.
Then finish the floor with another coat to seal the grout as well.
Harris is the product training director for a manufacturer of engineered
systems for architectural concrete and conducts training seminars around
the world. He holds three ACI certifications and is a Board Member o f
the ASCC's Decorative Concrete Council.
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