How to Acid Stain Gypcrete or Any Gypsum-Based Underlayment

These days, staining both old and new concrete surfaces with acid stains (also called reactive stains or chemical stains) is very popular due to its unique appearance and cost-effectiveness. Acid staining is a process in which an aqueous solution of metal oxides and inorganic acid is sprayed onto an existing concrete surface. The acidic metal oxide solution reacts with the lime (calcium hydroxide) present in the concrete and produces insoluble colored compounds that become a permanent part of the concrete. Therefore, one of the basic conditions in which the coloring of concrete with acid dyes will work is the presence of lime in the concrete. Often, lazy people who just bought a house or condo, remove the carpet or vinyl tile and find something underneath that they think is concrete. When they spray the acid stain or reactive stain and expect to be disappointed because they don’t see any change in the color of their concrete surface. This is because the substrate that looks like concrete is, in fact, plaster-based ‘Gypcrete’. Builders often use this on upper floors to level subfloor areas and provide a good base for other types of floor coverings. Unfortunately, staining Gypcrete does not produce any desirable results since it does not contain lime; In addition, it is too soft and wears out easily. Therefore ‘Gypcrete’ cannot be used as a wear layer.

Since Gypcrete surfaces cannot be used as a wear layer and acid stains do not work on them, it is common practice to apply a 1/16-inch polymer-modified concrete surfacing material (also called microfinishing or Thin layer). Find below the steps required to resurface Gypcrete and acid stain with a final microcoat or skim coat:

has. Sweep the surface of Gypcrete and dry vacuum the surface thoroughly. Rake the joints where the drywall meets the floor. Clean adjoining areas, even those not resurfaced, with microtopping.

b. Install masking paper (plastic) at least 48″ high on surrounding walls. Spray a light mist of water only to wet surface (DO NOT FLOOD!)

Against Using a new rayon mop, apply the first coat of acrylic primer (Cp1000) after being diluted 1:1 with water. After waiting at least 60 minutes, apply a second coat of diluted acrylic primer and cure overnight (or 10 hours minimum) before proceeding to the next step.

d. Apply another coat of acrylic primer, this time undiluted, and let it dry for 30-60 minutes. The third coat of primer can be applied with a garden sprayer (ie available at Home Depot or Lowes).

me. Apply a thin layer (1/16″) of polymer-modified microsurfacing or overlay using a magic trowel. Follow the link for specific instructions on applying polymer-modified microsurfacing, Sgrafffino. Allow microsurfacing to cure for at least 24 hours In cool, humid conditions (basements), wait at least 48 hours before proceeding to the next step.

F. Apply acid stain over completely dry microtopping. Follow the link for specific instructions on applying an acid stain, Patinaetch. Allow the acid-stained surface to dry for at least 24 hours before proceeding to the next step.

gram. The microtopping should be protected with a good quality sealer. Apply a coat of water-based epoxy sealer, Perdüre E32, followed by another coat of water-based polyurethane, Perdüre U46. Allow at least 6 hours between the application of the epoxy primer and the polyurethane topcoat. The sealed surface will be ready to use after 24 hours. Of course, at least 3 days are needed for complete healing.

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