Advice on Using Chemical Strippers

Question:
What is the best way to chemically strip sealers from concrete.

Answer:
The issue of stripping sealers is never at the forefront of what I write about, but in some cases it is required in order to repair or complete a specific decorative project.

The first thing that needs to be clarified is what a chemical stripper is and how these strippers work. Too often I get asked which solvent I recommend for stripping a sealer. First and foremost, solvents are not strippers! A solvent may loosen a sealer or coating, but left alone after spraying, the solvent will have little to no long-term effect on the sealers commonly used in the decorative industry. Using a solvent to eliminate trapped moisture or rewet the surface is a whole different process, and is covered in other blog entries (read Blisters, Bubbles on Sealer Surface and Preventing Moisture Problems). A chemical stripper is a chemical compound that actually destroys the coating, usually turning it into sludge. Another common misconception is that an acid will remove a sealer. Most common acids (such as hydrochloric and phosphoric) will have no effect on cured acrylics, polyurethanes or epoxies.

Strippers come in many forms, but they all have one thing in common. They need time to work and have to stay wet to stay active. Depending on the type and thickness of the sealer being removed, multiple stripper applications and hours of dwell time may be needed. Once strippers dry out they stop working. This is why most strippers are in gel form, because they hold better to most surfaces and they hold in moisture, allowing them to stay active longer. Today, you have a choice of environmentally friendly strippers, such as natural soy and citrus-based products, or the good old-fashioned methylene-chloride-based strippers that will take the skin off your fingers given the chance. While the environmentally friendly strippers are safer to use, they require more time to work. No matter what type of stripper you use, read and follow the manufacturer’s instructions. Be sure to protect anything you don’t want to strip, and be prepared for a pretty miserable job.

Here are a couple of tricks I have learned over the years that can make stripping easier:

• Use a walk-behind scrubber or rotary floor swing machine with a soft- to medium-bristle brush to help remove all the stripper and sealer sludge. Protect the machine with plastic, and use brushes that are resistant to the chemical strippers.


• Another method that I heard about from a contractor, tried myself, and found to be quite clever is to create a chemical stripper “cooker” using wet cotton sheets. First, soak the sheets in water and ring them out until they are damp. Apply a uniform layer of chemical stripper over the concrete surface and then cover the surface with the damp sheets. Make sure to get as much contact as you can between the sheet and the surface, pushing the sheet down into the grout lines and deep textures. Cover the damp sheets with a sheet of plastic, and seal the ends as best as possible to keep the moisture in. Let this sit for hours, and if all goes well, the active stripper will liquefy the sealer, and via osmosis, the sealer sludge will soak into the sheet, greatly reducing the cleanup required.