How to Acid Stain Concrete Floors
HOW CONCRETE ACID STAIN WORKS
Concrete Acid Stain is a water-based liquid bearing minerals and acid.
The acid stain penetrates the pores of the concrete forcing a chemical reaction between the muriatic acid and the available lime in the surface.
Once acid stained, the color of the concrete is permanently altered.
When sealed with an appropriate concrete sealer and for indoor applications, sealed and waxed, acid stain produces the unique, variegated finish associated with this process.
BEFORE ACID STAINING
Surface preparation is the most important step in the acid staining process. Prior to staining, a slab must meet the following criteria:
The concrete must be free of debris, dirt and oils, paint, dry wall mud, adhesive, sealers, stains of any kind or similar materials. Acid stain cannot react properly with the concrete if these conditions are present.
The slab should not have been treated with a waterproofing agent, cleaned with muriatic acid or a heavy trisodium phosphate (TSP) solution. The acid stain reaction cannot occur on surfaces treated with these products.
Newly poured concrete can be acid stained anytime from 20-28 days after the pour or once the concrete has achieved a uniform light gray color.
For older, excessively power-washed, or mechanically-profiled concrete, the surface must be completely intact with no exposed aggregate or sand particles. Concrete acid stain does not stain rocks, sand or aggregate.
Exposed aggregate or otherwise depleted concrete may cause the acid stain to take irregularly, react weakly or produce a color inconsistent with the acid stain color chart.
Slick, machine-troweled concrete requires mechanical or chemical etching for a complete acid stain reaction to occur. If water beads on the surface or dark gray areas caused by excessive troweling are visible caused by excessively troweling, DC Hard Troweled Floor Prep should be sprayed on the concrete or the surface should be sanded using an 80-grit sanding pad prior to application.
Newly poured concrete slabs and countertops should include less than 10% fly ash to insure a good chemical reaction with the acid stain. Check with your ready mix company or read the countertop mix MSDS for concrete additive information.
Concrete poured with excessive water in the mix can create a thin, unstable layer of concrete on the slab surface. To test for instability, press the tip of nail into the concrete. If breaking or damage of any kind occurs, the slab must be profiled with a concrete grinder or a high-speed buffer using a 60-80 grit sanding disc before
Often, concrete surfaces will have dry wall mud, paint, wood stains, tile adhesives, carpet adhesives, grease, pet stains, etc. on the concrete.
Concrete Acid Stain is not an over coat, but is an opaque, penetrating color that permanently changes the appearance of the concrete. Areas where debris remains on the surface will likely not accept the stain leaving color imperfections on the floor, particularly mastic, dry wall mud and paint.
• Use Bean-E-Doo, for the removal of adhesives.
• Apply Soy Gel Professional Paint Stripper to remove epoxy, sealers, varnish or paint.
• Use Xylene to remove solvent-based sealers and clean up sprayers or tools.
• Use soap and hot water to remove water-based sealer from applicators immediately after application.
The vast majority of slabs only require minimum cleaning with an organic degreaser diluted at a medium concentration with water. Scrub the surface with a soft nylon bristle brush or power wash on a low setting to prepare most floors for staining.
Thoroughly rinse the surface with clear water to remove any remaining cleanser and leave the floor to dry. For projects, use a shop vacuum, mop and/or squeegee to contain the water and aid with drying.
Cleaning floors that have been heavily soiled or have been previously tiled or carpeted to a stainable level is a considerable amount of work, but not impossible. Concrete overlay is an excellent solution for patched surfaces, exposed aggregate or otherwise unsightly concrete to provide a more attractive final result using acid stain.
APPLY CONCRETE STAIN
Safety First! Remember to use goggles, gloves and a dust mask while working with concrete acid stain. A respirator may be required for applications with poor ventilation.
The appearance of the finished product is very much influenced by the manner in which the acid stain is applied. We recommend spraying the stain on the surface using an all-plastic pump sprayer.
If a darker, more even tone is desired, brush the acid stain into the surface using consistent circular strokes.
If using a brush, spray on a second coat to eliminate any brush strokes on the surface unless that is the desired finish.
Though new concrete may not always require a second coat of acid stain, older concrete does require two coats of stain for complete coverage.
For a more diffuse look, spray the stain onto the surface without brushing.
Apply one heavy coat of your base color and immediately apply accent coats while the stain is still wet to encourage a more natural appearance on the slab.
Continue to apply the lighter to darker colored accents until satisfied with the results.
For a “marbled look”, spray enough stain on the surface to allow the color to naturally run and pool in the lower areas of the concrete.
Applying the Concrete Acid Stain with the sprayer nozzle close to the floor will produce “pooling” effects.
For a multi-colored effect with distinct areas of color, begin with your lightest color as a base coat. Visit our projects page for more ideas
Base coat colors can either be a light acid stain color such as Azure Blue, Malayan Buff or one of the darker stains cut with water.
If walking on wet acid stain, wear acid resistant spiked shoes to avoid leaving foot impressions on the floor.
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Direct Colors DIY Concrete Acid Stain Kit has all the products, tools, and cleaning materials you’ll need for 200 sq. ft. concrete floors