DIY Acid-Etched Concrete Stain

Acid-based concrete stains are topical stains applied directly to any concrete surface. They are generally earth-toned in shades of reds, greens and browns. When applied creatively, acid stains mimic the look of more expensive materials like stone and marble. Acid stains are a mixture of water, hydrochloric acids and metallic acid-soluble salts that penetrate into the pores of the concrete and react chemically with the lime in the concrete. Because of this chemical reaction, the acid stain is a permanent feature of the concrete, resistant to chipping, fading and peeling.

Things You'll Need

• Protective clothing
• Painters tape
• Plastic sheeting
• Metal scraper
• Large deck brush
• Plastic bucket
• Oil and grease emulsifier or trisodium phosphate
• Shop-vac
• Pump-action nozzle sprayer with plastic tip
• Baking soda
• Solvent-based acrylic sealant
• Concrete floor wax
• Lamb's wool applicator

Instructions

Surface Preparation

1. Tape off the surrounding surfaces. Hang plastic sheeting to protect surfaces from splatter and water absorption.

2. Remove gummy materials of oil or sediment with a metal scraper. Sweep the concrete surface to remove dirt and debris.

3. Clean the surface with oil and grease emulsifier or a mixture of water and trisodium phosphate (TSP). Scrub the cleanser into the concrete with a deck brush. Let the product work for 15 to 30 minutes, then rinse the floor with clean water.

4. Remove the water with a shop-vac. Let the concrete surface dry thoroughly for at least 24 hours.

Surface Staining

1. Mix the stain according to the manufacturer's directions in a plastic mixing bucket. Some stains come pre-mixed as a single component, which are easier for most do-it-yourself homeowners.

2. Pour the stain into a pump-action nozzle sprayer with no metal tips or internal parts that can come into contact with the stain.

3. Spray the concrete acid stain on the floor in circular motions. Have a friend follow behind scrubbing the stain into the concrete with circular motions.

4. Apply a second coat quickly over the brushed areas to reduce the appearance of brush strokes in the finish.

5. Continue applying acid stain to the rest of the concrete surface, spraying and scrubbing in a circular motion as you go. Work down the length and then in reverse, overlapping rows. Do not let the edges of adjacent rows dry while you are working. Always apply stain wet on wet and in uniform coats.

6. Let the first application to the whole surface dry completely. Add another coat of acid stain for an intensified color or another stain color for a marble effect. The stain should have at least four hours or more of reaction time with the concrete, though this may vary by product.

Neutralizing the Acid Stain

1. Mix baking soda and water thoroughly. Use 1/2 cup of baking soda per gallon of water.

2. Pour the mixture directly onto the acid stain.

3. Scrub the baking soda neutralizer into the concrete to remove the acid residues. Vacuum the water as you scrub the concrete to remove the residue immediately as it floats on the water.

4. Rinse the concrete with clean water, scrubbing and vacuuming the water immediately. Repeat this step at least two or three more times to remove the residue. If any residue remains, it interferes with the sealers.

5. Allow the concrete surface to dry completely, at least 12 to 24 hours.

Protecting the Acid Stain

1. Mix the solvent-based acrylic sealant according to the manufacturer's instructions.

2. Spread a very thin layer of the sealant onto the concrete surface with a clean spray nozzle. Apply the sealant with circular motions, up and down the length and overlapping edges. Again, keep the edges wet to avoid double layers and seams.

3. Let the first layer dry.

4. Apply a second very thin coat of the sealer, using the same method. Let this layer dry as well.

5. Apply a layer of concrete floor wax by dumping a small amount onto the concrete. Spread the wax with a lamb's wool applicator. Allow each coat to dry before adding subsequent coats.

Tips & Warnings

• Surface preparation is vital. Acid stains are transparent and any surface defects will show through and possibly be intensified once the stain and sealer go on. Remove or repair as much of the concrete surface as possible before staining.

• If the edges of the acid stain application layers dry and you make another sweep over it, you will create seams from the added layer of stain which will show through finish.

• Do not let the acid stain pool on the concrete surface. This will create a noticeable color difference.

• Apply the sealer wearing socks instead of shoes to avoid tracking dirt onto the surface. In addition, if you happen to step on a tacky section of sealer, shoes will lift the tacky spot. Socks will not.

• Concrete absorbs stains differently and the look of the finished product will be marbled with a varied amount of coverage and color. The newer the concrete the better the acid stain reacts and looks.

• Do not use metal tools or nozzles with acid-based stains. Acid damages metal surfaces and affects coloring of the concrete.

• Do not clean the concrete with acid etches or washes. This will react negatively with the concrete and the acid stain.

References

• Concrete Ideas: How to Acid Stain Concrete
• Concrete-Stain: Do-it-Yourself Concrete Acid Stain
• Concrete Netwrok: Stained Concrete - The Art of Acid-Etch Staining
• Epoxy Concrete Coatings: Creating Unique Concrete Floor Designs with Acid Etching