Acid stains belong to a class of materials called reactive stains. These stains do not use pigment to color concrete. Instead, they chemically react with calcium hydroxide (lime) in the concrete to change color. This leads to rich, amazing, and durable color. Beauty comes with a price, however. As the color change is reliant on a chemical reaction, it may be hard to predict or control. Read on to see how Brickform Blush Tone Acid Stain was used to stain a basement floor.

The floor in question was a relatively new placement. The homeowner planned to finish the basement and turn it into a family room with bathroom. By staining the floor, the homeowner would have an attractive floor without needing to purchase and install additional flooring materials. This concrete floor presented a number of things to be wary of. Non-uniform finishing, stains, and contaminants would all need to be considered as they would affect how, or if, the stain would react.  Each of these anomalies would need to be considered.

Safety and Precautions

Acid stains contain hydrochloric acid. As such, precautions need to be taken to protect applicators and the environment. All tools that come in contact with the material should be acid resistant. Applicators need to wear appropriate safety gear – gloves, eye protection, boots etc. – when mixing and applying the stain. Ensure the area is properly ventilated and masked, with sensitive items like electronics protected.  Always read the technical literature for the products you plan to use and follow the safety instructions carefully.

Sampling

It’s impossible to predict exactly how an acid stain will react, but sampling helps give some idea. Create several small mock-ups on an inconspicuous part of the slab. In this case, John tried a handful of color and technique combinations under a staircase, on a part of the slab that would later be walled off. The homeowner circled their favorite option. John made sure to use the exact same surface preparation, stain application, and sealing on the samples as he would on the full-scale project.

Surface Prep

As with any other decorative concrete application, surface preparation is key to the success of any acid stain job. The rule of thumb when prepping for acid staining is to prepare the surface for the sealer. Clean the surface to remove any contaminants then profile the surface to the sealer specifications. John determined that a simple cleaning with Brickform E-Etch and Neutra Clean would be sufficient for this floor. He also conducted a calcium chloride test to make sure the surface would meet the requirements for his chosen sealer.

Mixing

Unlike many products, acid stains do not require much mixing. You should only need to mix acid stains when you are using multiple lots of material and/or you are diluting the acid stain. Intermixing different lots is important to ensure consistent color and reaction. Whenever you mix acid stains or transfer them to a new container such as a bucket or sprayer, do so with proper protection. Wear gloves and eye protection to prevent acid related injuries. Protect the floor from spills or drips as well. The stain will begin reacting as soon as it makes contact and it cannot be cleaned up. Even if the surface is going to be stained in the future, accidental spills or drips will likely show through.

Application

Acid staining is a bit of an art form. The key to success is to replicate your technique used during the sampling process. Every applicator on the jobsite should know exactly what he needs to do and the whole team should work together. Apply the stain liberally to dry, properly prepared concrete. Maintain a wet edge until you have reached a good stopping point such as a control joint. Brush the freshly applied stain in a circular motion to avoid spray and drip marks. Do not allow stain to drip or come into contact with anything you do not wish to color.

On this project, John and Todd used multiple colors for a marbled effect. The primary color came from a 1 to 1 dilution of Ebony with water. John also applied diluted Turquoise in a smaller sprayer. Todd followed and scrubbed the stain for even coverage. John and Todd practiced and got their technique down on an inconspicuous part of the project. This was important because they needed to work in concert. Had they made any mistake – such as stepping on stain, stopping too long, or failing to scrub a portion in time - they could have potentially ruined the project. The following day, John and Todd came back for a second application of stain hoping for a stronger, more vibrant color. John used smaller spray bottles to apply undiluted Turquoise and Olive highlights. Todd followed with more diluted Ebony. After letting this second application react for a couple hours, they came back for residue removal.

Residue Removal

One of the most important steps of acid staining is residue removal. Acid stain residue is almost always ugly – follow this link for our article about managing expectations when acid staining. More importantly, acid stain residue causes sealer failure. Even a small speck of residue can cause sealer to delaminate, white, or otherwise fail. First you need to neutralize the stain to stop the acid reaction. Brickform Neutra Clean is a good choice because it acts as a neutralizing agent as well as a mild cleanser. Scrub the residue and immediately remove it from the slab. On interior projects, such as this one, you will likely want to use a rotary floor scrubber and a heavy duty wet vac. Exterior jobs can use stiff bristle brooms and power washers. In any case, do not let it dry before the loosened residue is removed, otherwise it will re-adhere. Continue rinsing, scrubbing, and removal until the rinse water runs clear and all residue is removed.

Touch Up

This is what separates a good job from a great job. Stains don’t always react how you expect… or at all. Penetrating stains and dyes really come in handy at this point. Being non-reactive, these stains and dyes need only to be able to be absorbed into the material in question. Whether you use penetrating dyes or water based stains, make sure to read the appropriate TIS and follow the included instructions.

On this project, John and Todd were going for more of an industrial, distressed feel. Still, they found it necessary to do some minor touch up work around the most glaring defects. They applied Brickform Pro-Dye with small disposable sprayers. Where possible, they sprayed the Pro-Dye directly onto the blemish. Other spots, they had to “feather” the dye around spots that would not accept color.   

Sealing

Use a decorative concrete sealer for a long life and brilliant appearance. High quality sealers enhance color with either a matte or glossy finish. Make sure to match the sealer to your application and follow applicable application instructions. On this project, John chose to use Brickform Decopoxy for a durable, high gloss finish perfect for acid stained floors. He used a ¼” knap microfiber roller to apply the Decopoxy, crosshatching and backrolling to minimize roller lines. After the first coat had cured (about 6 hours in most applications, never waiting more than 24 hours), he applied a second coat. Afterward, John applied Brickform Premium Acrylic Floor Finish as a glossy, protective sacrificial coating.