Acid staining a basement floor that has been painted or sealed
Contrary to paints or coatings that produce solid, opaque tones, acid staining produces rich, deep, translucent tones.
Based 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. 
Chemical stains (or acid stains) react with the concrete's lime content to create color.
Paint or sealing the concrete surface will prevent acid stains from penetrating and reacting with the lime.
Acid stains cannot be applied to painted or sealed concrete surfaces.
To acid stain concrete, do you have to remove the paint or sealer first?
Not necessarily!
The newest acrylic polymer modified concrete makes it possible to apply a thin layer (1/8inch thick) of concrete over an existing painted or sealed concrete surface with minimal surface preparation.
Listed below are typical steps involved in applying a micro-topping / concrete overlay and acid staining over painted or sealed concrete.
A: Sand the entire surface with a 60grit sanding screen. To ensure that the paint or sealer is bonded to the substrate, run the sander for at least 1 hour per 1000 square feet.
B: Rinse the floor thoroughly with mild detergent and allow it to dry completely.
C: Coat liberally with acrylic primer, Cp1000.
D: Let the primer cure overnight (at least 10 hours).
F: Paint a second coat of acrylic primer, Cp1000. Apply the second coat just enough to dampen the surface.
E: Once the primer has turned clear and is dry to the touch, it is ready for the concrete overlay.
G: Apply the Pentimento polymer modified concrete overlay at 1/8 inch thickness. It is a retroweldable concrete overlay that gives the concrete a very smooth finish.
H: Once the polymer concrete overlay has cured for 24 hours, it is ready to be stained with acid (chemical stains).
Dry the surface for at least 24 hours before sealing it with one coat of water-based epoxy, Perdüre E32, and one coat of water-based polyurethane, Perdüre U46.
I: Spray the acid stain, Patinaetch, at a rate of 250 feet per gallon. You should allow it to react with the lime in the concrete for at least 2-3 hours.
Remove the residue according to standard procedures. Make sure to clean the residue and neutralise the surface with ammonia.
J: Allow the surface to dry for at least 24 hours, before sealing it with one coat of water based epoxy, Perdüre E32 and one coat of water based polyurethane, Perdüre U46.
Pentimento does not solve the moisture emission problem.
Before applying Pentimento and acid staining with Patinaetch, it is highly recommended to conduct a MVER test.
Concrete resurfacing is faster and sometimes less expensive than grinding off the paint or sealer.
The results of acid staining are not guaranteed, even if they can be removed from the surface. Resurfacing concrete is the best option!
