How to Acid Stain a Concrete Floor

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If you're looking for a durable, high impact flooring option that won't totally break the bank, consider a do-it-yourself acid staining project. Muriatic acid, available in a variety of colors, penetrates concrete and reacts to the lime deposits, coloring the surface and giving a unique mottled, swirly finish.

No two acid-stained floors will be the same! But everything can be done by even a beginning DIYer. Depending on the amount of preparation your surface needs, you can get this unique, durable flooring option for as low as .60 cents a square foot, including all the tools needed to apply the finish. For a large area and a small budget, this is the perfect solution.

(Image: Machelle Vanderhoeven)

(Hey, like the look of this cool fireplace in these photos? Learn how to update a rock fireplace by using paint with this simple tutorial.)

Things You'll Need

  • Acid stain (We used Eagle brand acid stain in the Aquamarine color)
  • Degreaser/Neutralizer (or liquid ammonia) (We used Eagle brand Degreaser & Neutralizer)
  • Floor sealer (We used Eagle brand acrylic sealer)
  • Floor polish (We used Eagle brand interior concrete polish in gloss; it's also available in matte)
  • Etch and clean
  • Synthetic broom brush
  • Plastic pump sprayer
  • Rubber gloves
  • Protective eyewear
  • Protective face mask
  • Water
  • Shop vac
  • Masking paper
  • Tape
  • 3/8" nap roller (2)

Tip

  • The state of your concrete surface, as well as the brand of acid stain you chose will determine exactly how many products you need. For example, some brands of acid stain strongly recommend against the etching and cleaning step, whereas other brands state it as necessary for their product to properly seep into the surface. The brand chosen here was done on the basis that it was available at a large national retailer and therefore easier to get and return if needed.

Step 1: Prepare Your Surface

This is the most variable step, depending on the status of your concrete. The basics to know is that your concrete must be clean, and any impurities will show through the acid stain. Acid staining is not an opaque coating, it is semi-transparent. So paint drips and the like will show through.

Some of these impurities will give your floor added depth and dimension, and having them show through will only add to the look you're going for. Others, if they are too intense, it may distract from the look of the floor. An example of this would be carpet glue which is generally laid out in a swirly, unpredictable pattern and will be very obvious through your stain. There are appropriate steps to remove most impurities, so do some research and determine what may help you achieve the look you want.

Our floor before taking steps to prepare it
Our floor before taking steps to prepare it (Image: Machelle Vanderhoeven)

Our floor required a mixture of grinding, filling divots with concrete crack filler, using acid cleaners, filling and leveling out tension breaks in our floor, sanding and scraping. In the end we were left with a surface that was far from perfectly smooth but that we knew would work for the look we were going for.

After cleaning up the surface and removing some impurities
After cleaning up the surface and removing some impurities (Image: Machelle Vanderhoeven)

Step 2: Clean the Concrete

No matter the brand of stain you use, your concrete needs to be pristine before the application. Using a pressure washer here is very effective but not necessary. Simply going over your surface with the plastic pump spray filled with water and then scrubbing it with a push broom, rinsing again with water and allowing to fully dry is perfectly effective. Using your shop vac to vacuum up the water will speed up drying time significantly. Even using some mild soapy detergent is okay in this step.

For the brand we used (Eagle), it was recommended to go over the surface with their Etch & Clean product after this initial cleaning step. To do this, wear your protective gloves and then mix one part Etch & Clean with four parts water in your pump sprayer. Spray this onto your floor, allow to rest for a few minutes (you will hear it fuzzing) and then scrub over it with your synthetic broom.

Applying mixture of Etch & Clean and water
Applying mixture of Etch & Clean and water (Image: Machelle Vanderhoeven)
Brush the cleaner well into your concrete
Brush the cleaner well into your concrete (Image: Machelle Vanderhoeven)

Rinse the surface with clean water and vacuum it up. And then rinse and vacuum again to make sure you've cleaned up as much of the residue as possible. If your surface is outside, you may not need to vacuum, just thoroughly spray the surface off with clean water.

After rinsing, vacuum up water
After rinsing, vacuum up water (Image: Machelle Vanderhoeven)

Allow the surface to completely dry, preferably for 24 hours or longer.

Step 3: Apply the Acid Stain

First prepare your room by masking off all surfaces and walls that you do not want to get acid on them. You can find different widths of masking paper in the painting section at home improvement stores. Use tape to attach this.

(Image: Machelle Vanderhoeven)

Pour the acid stain directly into your clean pump sprayer. The application process will be much easier with two people but it isn't necessary.

(Image: Machelle Vanderhoeven)

If you have two people, one person should spray on the acid stain, in a semi-unpredictable pattern, going back and forth in different directions while the second person follows behind with the broom, scrubbing the acid stain into the surface. The sprayer can then go back over as needed to cover any brush marks or spots that appear to have less coverage.

(Image: Machelle Vanderhoeven)

If you are doing this on your own, just apply a small area, about 3 feet by 3 feet, and then go over and brush it in and then respray to cover brush marks and move forward, again in a varying pattern across your floor.

Remember to plan for an exit strategy where you won't have to step over your acid stain. Any steps will show up through the stain so if this happens, be sure to brush and spray over the footprint.

Step 4: Wait for the Desire Color and Apply More Coats as Needed

Your acid stain will continue to deepen and develop into your concrete for several hours, probably about ten. You may be happy with the color after just one though. Each surface will penetrate differently so there is no right amount of time to wait other than just when you are happy with the look of it.

For our floor, we determined a second coat of acid stain was necessary after waiting overnight and desiring a darker color. The same application process was used and we waited about 24 hours on the second coat which gave it a really dark finish.

Step 5: Remove Acid Stain

When you are happy with the coloring of your floor, you'll need to neutralize the surface to stop the staining process.

To do this, there are ready-made products like the one by Eagle that we used here called Degreaser & Neutralizer, or you can get the same effect by mixing one part liquid ammonia with one part water.

(Image: Machelle Vanderhoeven)

Pour your neutralizer onto the surface and scrub it in with your broom or a mop.

Tip

  • We used a yarn mop and if we were to repeat this process, we would just stick with our broom as some of the yarn came off and left debris.

(Image: Machelle Vanderhoeven)

The easiest method for clean up on a large area is as follows: spray over with clean water, brush puddles of water into one general area, say the middle of the floor. Then use your shop vac to go over and vacuum up all the puddles. Repeat this process at least once more, possibly twice more, until the water is no longer the color of your stain. After the last time you've vacuumed up puddles, go over the whole room with your vacuum to get as much of the water up as possible.

(Image: Machelle Vanderhoeven)

Step 6: Apply Seal

When your floor dries, it will be remarkably lighter than it will look like after the seal and polish have been applied, so don't be alarmed if it looks different than you were hoping. At this point we also removed the masking paper on our walls.

There are multiple products of sealer you can use, but the one we found that is readily available and had the best consumer reviews was the Eagle brand acrylic sealer.

There are multiple ways of putting this product down, we used a 3/8" nap roller on an extended arm and got great results. Consult the product bottle to get other options for spreading it on.

We decided to pour our seal into a paint pan and then roll it on from there. Apply it in thin layers, and you can do multiple layers if needed. We did two coats of sealer. You can see that the seal immediately makes the floor a lot darker. Allow to fully dry overnight.

(Image: Machelle Vanderhoeven)

Step 7: Apply Polish

Polish gives another layer of protection for all of your hard work. Additionally, you can choose a gloss coating that will leave you with a nice wet look. Again, we stayed with the Eagle brand interior concrete polish in gloss; it is also available in matte.

This process is important to do quickly and thinly so you don't get a milky finish. Pour the polish directly onto the concrete in a small puddle and immediately disturb the puddle with your roller or mop, pushing it forward and backward in a thin layer. Remember an exit strategy. Don't be too worried if you have a slight milky surface when you finish, this should go away after just an hour or two.

(Image: Machelle Vanderhoeven)
(Image: Machelle Vanderhoeven)

Allow to dry for 1 to 2 hours and then apply more coats as desired. We did four coats total. One gallon of polish did this for us over a 325-square-foot area with some left over. A little goes a long way! This product doesn't give a very "wet" finish, so if you're looking for more of a glass type surface, you may need to research a gloss coating made for outdoor use.

(Image: Machelle Vanderhoeven)

As you can see, acid staining gives a really mottled finish, inconsistently coloring the floor throughout, which is the appeal. Acid-stained surfaces are ideal for any location. They are perfect for restaurants and many retail locations but can also be eye catching for your home. And, this finish is exceptionally cheap compared to other new floor coverings, which can be a great solution for anyone!

(Image: Machelle Vanderhoeven)
(Image: Machelle Vanderhoeven)

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