Acid staining concrete produces rich, deep, translucent tones unlike paints or coatings that produce a solid, opaque effect. Depending on the color and application techniques used, the results can mimic everything from polished marble to tanned leather to natural stone or even stained wood. The chemical stains (or acid stains) react with the concrete’s lime content and produce the color. If the concrete surface is painted or sealed, acid stains cannot penetrate the concrete and react with the lime. Therefore, a concrete surface that is painted or sealed cannot be acid stained.
Do you have to remove the paint or sealer from the concrete surface to acid stain it?
With the advent of latest acrylic polymer modified concrete, it is possible to apply a thin layer (1/8inch thick) of concrete over an existing painted or sealed concrete surface with minimal surface preparation. Please find below typical steps involved in applying a micro-topping / concrete overlay and acid staining over a painted or sealed concrete surface.
- Run a sander with 60 grit sanding screen over the entire surface. To ensure that the paint or sealer is bonded to the substrate, run the sander for at least 1 hour for every 1000ft2.
- Rinse the floor with mild detergent and allow it to dry completely.
- Apply a liberal coat of acrylic primer, Cp1000.
- Allow this primer cure overnight (at least 10 hours).
- Apply a second coat of acrylic primer, Cp1000. The second coat needs to be applied just to damp the surface.
- Once the primer turns clear and it is dry to touch, it is ready to accept the concrete overlay.
- Apply the polymer modified concrete overlay, Pentimento at 1/8 inch thick. It is a retrowelable concrete overlay…which gives a very smooth concrete finish.
- After 24 hours of the curing or polymer concrete overlay, it is ready to take acid stains (chemical stains).
- Spray the acid stain, Patinaetch at the rate of 250ft2/gal. Allow it to react for with the lime in the concrete for at least 2-3 hours. Follow the standard process of cleaning off the residue. Pay particular attention to cleaning the residue and neutralizing the surface with ammonia.
- Allow the surface to dry for at least 24 hours, before sealing it with one coat of water based epoxy, Perdure E32 and one coat of water based polyurethane, Perdure U46.