Acid stain is muriatic acid with a color pigment added to it. When you put the acid on the floor, it opens up the concrete and allows the color to penetrate, so the color becomes part of the makeup of concrete rather than sitting on top of it.
Acid staining can be done in new homes with freshly poured concrete floors and patios and in older homes with plain or worn-out concrete slabs.
You can stain indoor or outdoor concrete floors.
Of all the decorative processes for concrete, acid staining is probably the best suited for the handy do-it-yourselfer.
- Dress properly for the job. Cover your eyes, nose and feet. Wear long sleeves and long pants.
- Test your color on a small patch of the slab that’s hidden from view. The color will look different on your slab than it does on a neighbors because some concrete is more porous and absorbs color better than others. The stain is permanent.
- Clean your concrete slab with care. Power-wash it and scrub out stains. Stain will hide small imperfections, but most show through.
- If your concrete is damaged and stained, or if you want to change the color of a previously stained slab, you may have to put down a “scratch coat”—an overlay made from modified polymer concrete. New or clean slabs don’t usually need this “new skin.”
- Spray on one to three coats of the acid stain.
- Neutralize the acid with a wash of ammonia and water. You can dump the mixture onto the acid-stained floor and scrub or mop it down. This step helps the sealer adhere.
- Wait for the floor to dry completely before topping the stain with an epoxy sealer. You can choose a thick, glass-finish coat or a flatter, matte finish.