How To: Acid Stain Concrete
Go from gray to gorgeous with this simple technique to impart your patio, floor, or countertop with deep, stylish color.
Concrete is durable, dependable—and, naturally, a bit cold in tone. If this steely neutral isn’t your style, you can update your patio, basement floor, or concrete countertop in a range of eye-catching colors using acid stain technology. Metallic acid salts and hydrochloric acid in the stain penetrate the surface and react with concrete’s natural lime content to impart deep hues that won’t fade or peel off.
Acid stain is available from home improvement centers for about $60 per gallon and can also be ordered online. To determine how much you may need for your particular project, consider that a gallon of stain will cover approximately 200 square feet of concrete. Then, choose from a dozen or so translucent colors including earthy browns and tans, rich greens, deep golds, rustic reds, and terra cotta tones that complement concrete both outdoors and in. The finished result is a striking marbled effect that can be waxed to achieve an attractive satin sheen.
While the process for how to acid-stain concrete is fairly straightforward, each step should be performed carefully before going on to the next step. Concrete should be fully cured before applying acid stain, so if your surface is new, wait a minimum of 14 days before staining.
Clean the surface to be stained with a concrete cleaner labeled for use on the specific type of dirt or blemish you wish to remove. You might have to use more than one cleaner; a product designed for grease might not tackle paint splatters. For stubborn marks, such as hardened tar or paint, use a grinder (see Step 3).
Tip: Some grease can be difficult to see, so to spot it, lightly spray the surface with plain water. If the water beads up in spots, you’ve probably found grease stains.
If applying acid stain indoors, cover adjacent walls with plastic sheeting, held in place by painter’s tape and open windows for ventilation. Outdoors, protect any nearby siding, lamp poles, etc., with plastic sheeting and move patio furniture away.
Poured slab concrete isn’t meant to be perfectly smooth, but large protrusions (called “fins”) or rough patches should be removed before staining. Smooth the surface with a grinder (available for rent at construction rental centers) fitted with an abrasive silicon carbide disk.
Don your long sleeved shirt and long pants, protective goggles, and chemical-resistant gloves. Dilute the acid stain with water in a pump sprayer as directed by the stain manufacturer. Spray the concrete evenly, starting along one edge of the slab and working your way to the other side. For concrete countertops or other small items, you can mix the acid stain in a smaller plastic bucket and apply it with a regular paintbrush.
Immediately after spraying a strip, while the solution is still wet, use a natural-bristle push-broom to brush the solution into the surface of the concrete with even, back-and-forth strokes to create a uniform look. If you’re going for more of a mottled look, skip this step.
Allow the acid stain to penetrate the entire concrete surface and fully develop its color for from five to 24 hours (check manufacturer’s instructions for exact timing). The longer you leave the acid stain on, the deeper the final hue will be.
When the concrete reaches the desired color, apply an alkaline neutralizing solution such as trisodium phosphate (TSP)—which you can pick up in hardware stores—to stop the chemical reaction. This involves some elbow grease and a lot of water! Mix the TSP with water as directed on the container and apply the solution liberally to the concrete, scrubbing thoroughly with a heavy-duty push broom. If you’re working indoors, you’ll need a wet/dry vacuum to suck up the water solution as you go. Afterwards, rinse thoroughly with clean water. It might take three or four rinse cycles to remove all acid and TSP residue.
Once the stained concrete is clean and completely dry, apply a penetrating concrete sealer to protect the surface from stains. When purchasing sealer, read labels carefully to ensure you get the right product—an interior concrete sealer is not suitable for exterior use.
- Before applying acid stain to the entire concrete surface, test it in an inconspicuous area to ensure you like the color.
- If an acid stain manufacturer recommends a specific application tool, use it. They know their own product!
- Apply surface wax to interior floors or concrete countertops. Floor wax should be suitable for use on concrete. For concrete countertops, use a food-safe wax such as carnauba to coat the countertop and give it a lustrous sheen.