Concrete is durable and reliable—and, naturally, the color tone is a bit cold. If this steely neutrality is not your style, you can use acid staining techniques to update your patio, basement floor or concrete countertop in a range of eye-catching colors. The metal salt and hydrochloric acid in the stain penetrate the surface and react with the natural lime component of the concrete, giving it a dark color that will not fade or peel.
Acid stains can be obtained from home improvement centers and online. To determine how much your particular project might require, consider that one gallon of stain will cover approximately 200 square feet of concrete. Then, choose from a dozen translucent colors, including earthy browns and tans, rich greens, dark golds, rustic reds, and terracotta, which complement the outdoor and indoor concrete. The end result is an eye-catching marble effect that can be waxed to achieve a charming satin sheen.
It is not difficult to learn how to acid stain concrete. Before proceeding to the next step, please perform each step carefully. The concrete should be fully cured before acid staining, so if your surface is new, please wait 28 days before staining.
Acid stained concrete is a relatively simple project, but some basic knowledge is essential. You must first fully prepare the concrete surface, and then apply the stain evenly to prevent spots from appearing. It is also necessary to neutralize concrete acid stains, because concrete is naturally alkaline while stains are acidic. Knowing what will happen-and how this process works-will ensure a beautiful finish.
Unlike the paint on the top of the concrete surface, the acid stain penetrates into the concrete and injects a translucent tone, adding color to the natural concrete while revealing it. Depending on the type and technique of dyeing selected, various effects can be used, including imitating the appearance of hardwood or marble.
For simple full-tone applications, professional use of acid dyeing costs approximately US$2 to US$4 per square foot. Complex projects that involve mixing colors or creating patterns and textures will run more—ranging from about $12 to $25 per square foot. The price of a gallon of dye for a DIY project is approximately $60 per gallon.
Generally speaking, it takes about 5 to 24 hours from the use of an acidic dye to complete color development, depending on the brand of the dye and the manufacturer’s instructions. Cleaning and preparing the existing concrete surface will add another 2 to 5 hours to the project.
Clean the existing concrete surface with a concrete cleaner labeled for removing specific types of dirt or blemishes. You may need to use more than one cleaning agent; products designed for grease may not solve the paint splatter problem. For stubborn marks, such as hardened tar or paint, use a grinder (see step 3). If the concrete has a smooth machine smoothing surface, use a concrete preparation product designed to etch the surface, which will allow the stain to penetrate.
Tip: Some grease is hard to see, so to spot it, lightly spray the surface with clean water. If the water drops into small beads, you may have found oil stains.
If applying acid stains indoors, cover the adjacent walls with plastic sheeting, fix them with painter’s tape, and open windows for ventilation. When applying acid stains indoors, use a fan to help air circulate. The concentration of acid in acid stains is quite mild, but if any solution splashes on exposed skin during use, please rinse it off immediately.
Outdoors, use plastic sheeting to protect any nearby wall panels, light poles, etc., and remove outdoor furniture. Any porous object is as likely to absorb stains as concrete.
The poured concrete slab is not meant to be completely smooth, but large protrusions (called “fins”) or rough patches should be removed before staining. Use a grinder equipped with abrasive silicon carbide discs (available to rent at the building rental center) to smooth the surface. The grinder also helps to remove hardened tar and paint. If the existing concrete surface is smooth, use an etching solution.
Put on your long-sleeved shirt and trousers, goggles and chemical resistant gloves. Follow the stain manufacturer’s instructions to dilute acid stains with water in a pump sprayer. Spray the concrete evenly, starting from one edge of the slab and working all the way to the other side. For concrete countertops or other small objects, you can mix the acid stains in a smaller plastic bucket, and then apply it with a normal paintbrush.
In some cases, wetting the concrete before applying the stain will help it absorb more evenly, but please read the manufacturer’s instructions first to ensure that wetting is appropriate. Spraying concrete with a mist in a hose nozzle is usually necessary to wet the concrete. Don’t get it wet until it becomes a puddle.
Wetting can also help create artistic finishes by soaking one part of the concrete and drying the other parts. The dry part will absorb more stains and make the concrete look like marble.
Immediately after spraying the strips, use a natural bristle push broom to brush the solution into the concrete surface and tap it back and forth in a smooth manner to form a uniform appearance. If you want a more mottled appearance, you can skip this step.
In most cases, you will want to keep the “wet edges”, so don’t let some of the acid stains dry out before applying the rest, as this may cause noticeable lap marks. In other words, once you start the project, don’t take a break.
Let the acid stain penetrate the entire concrete surface and fully develop within 5 to 24 hours (check the manufacturer’s instructions for the exact time). The longer the acid stain is left, the darker the final tone. Some brands of acid stains react faster than others. However, do not allow the stain to stay longer than the maximum time recommended by the manufacturer.
When the concrete reaches the desired color, use an alkaline neutralizing solution, such as trisodium phosphate (TSP), which you can buy at a hardware store to stop the chemical reaction. This involves some elbow grease and a lot of water!
Follow the instructions on the container to mix the TSP with water, then apply a large amount of the solution to the concrete and scrub it thoroughly with a heavy-duty broom. If you work indoors, you need to use a wet/dry vacuum cleaner to suck up the aqueous solution at any time. After that, rinse thoroughly with clean water. It may take three to four rinse cycles to remove all acid and TSP residues.
Once the acid stained concrete is clean and completely dry, apply a permeable concrete sealer to protect the surface from stains. When buying a sealant, read the label carefully to make sure you get the correct product-internal concrete sealant is not suitable for outdoor use.
The finishes of the sealing machine are different, so if you want a moist look, choose a sealing machine with a semi-gloss finish. If you want a natural effect, choose a sealer with a matte effect.
Once the sealant has cured-it takes about 1 to 3 hours for permeable sealants and up to 48 hours for some types of local sealants-the floor or terrace is ready to use! No additional precautions are required.
Sweep or use a vacuum cleaner to vacuum dirty floors in the room or occasionally use a wet mop to keep it clean and well maintained. Outdoors, sweeping is fine, as is washing concrete with water to remove dirt and leaves. However, it is not recommended to use steam mops on concrete floors.
Yes, you can! Just make sure to peel off any existing sealant, clean the surface, and if the concrete is smooth, etch it.
Brushed concrete is one of the best surfaces for acid stains. However, first make sure it is clean and free of old sealant.
If the acid dye is not neutralized, it may not form a strong bond and may cause stains that must be peeled off and reapplied.
Of course, concrete of any color can be acid stained. But keep in mind that any existing color will affect the final color of the concrete.
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Post time: Sep-03-2021