Q & A – Cleaning Concrete Correctly for Acid Staining
Question: I have a concrete floor that’s a little smooth and has some paint on it. What’s the best product to clean concrete prior to applying acid stain? What should we avoid?
Answer: Cleaning your concrete correctly before acid staining is essential in getting a good final result. For example, if glue, paint or dry wall mud hasn’t been properly removed from both the pores and the surface of the concrete, white dots and streaks will be left behind after acid staining where the stain did not take and it’s not very attractive.
Cleaning Tip #1: If you have multiple contaminants on the floors, mechanically profile the concrete. It’s much more costly to apply more than one chemical stripper to remove paint, glue, dry wall mud and the like. Rent a high speed buffer with a sanding platform using a 50 grit pad or if the concrete is also very smooth, consider a concrete grinder available for rent at your local equipment rental supply. If you plan to grind the concrete, be sure to only remove as little of the concrete surface as needed and to avoid exposing sand, stones or large aggregate in the process. Acid stain will not stain aggregate and sand so proceed with care.
Cleaning Tip #2: If you have some isolated areas of glue or paint, a chemical stripper is a great option, but choose wisely. Chemical strippers often have very strong odors that can be difficult to use in enclosed spaces. Soy Gel Paint Stripper and Bean-e-doo Mastic Remover are both highly effective, low-odor products that can be safely used indoors. Remember that every chemical stripper leaves behind a heavy residue after use. Do not omit the degreaser and water solution cleaning step and thorough rinsing before continuing with your project. The residue will interfere with successfully staining and especially sealing if not properly removed.
Cleaning Tip #3: If your floor is very smooth and doesn’t allow water to easily absorb, you need to profile the concrete to open the pores to better receive the stain. Spraying muriatic acid or other acid-based etchers for this purpose or for cleaning will render your concrete unstainable. Etchers, such as might be purchased at big box retailers, are intended for use with water based stains and epoxy coatings NOT acid stains. Smooth floors can either by mechanically or chemically profiled to make them more suitable for acid staining. Again, if other contaminants are present, it might be best to sand or grind the floor. If not and no heavy duty cleaning is necessary, the concrete can be safely and easily profiled using DCI Hard Troweled Floor Prep prior to acid staining. Most floors finished with a machine trowel will require some kind of profiling for best acid staining results.
Surface Preparation Products: