Concrete Acid Stain |Certain Color Changes

RAC Azure Sky Concrete Acid Stain

RAC Azure Sky

Four of our Concrete Resurrection Reactive Acid Chemical Stain colors (RAC) have an asterisk beside them in our catalog and on our website. We often get questions about that, and we’d like to share the answers.




RAC Summer Wheat Concrete Acid Stain

RAC Summer Wheat

Which RAC stains have the asterisk beside the color names?

Olive Mist, Azure Sky, Mossy Oak and Summer Wheat


RAC Mossy Oak Concrete Acid Stain

RAC Mossy Oak


What does the asterisk mean?

It means those four colors are for interior use only because they contain copper atoms. All of the other RAC colors are for indoor or outdoor use.


What happens if I use one of the four marked colors outdoors?

Maybe nothing out of the ordinary. On the other hand, the outdoor concrete may turn a SHADE OF BLACK that may or may not be ugly depending on your point of view. It’s probably NOT what your customer was looking for though, or you either since it’s a permanent condition. Don’t risk it.

RAC Olive Mist Concrete Acid Stain

RAC Olive Mist

What causes the color change?

Oxidization causes the lovely color you started with to turn black. Outdoor slabs usually don’t have a vapor barrier underneath them so moisture from the ground migrates up through the concrete. When the water molecules reach the concrete acid stain, they react with the copper atoms in It and oxidize.

Could this same reaction take place on an interior floor?

Yes, if there is excessive moisture present. Interior floors usually have a vapor barrier though, and that prevents the problem. Always test the concrete with a moisture meter before you take any job regardless of the stain color. Know what you’re dealing with before you begin.

Have more questions about RAC stain? We offer free customer support to those using Concrete Resurrection stains. We don’t, however, answer questions about other brands of stain since we don’t know those products or how they’ll react in any given situation.

You can reach us by email at, use the Live Chat feature on our website, or give us a call at 800-884-2114 where a real person answers the phone.

Down by the River | A Decorative Concrete Transformation

Concrete Revival Jared Huber flagstone 2Now and then some really great before-and-after pictures of a decorative concrete transformation come along. Such is the case with this project by Jared Huber and Derek Farley of Concrete Revival, Irene, South Dakota.

Round concrete pad cracked and ugly



Jared and Derek were faced with a customer’s ugly, extremely cracked, circular concrete pad.



Cracked and ugly concrete slab.


Situated near the Vermillion River and sporting a fantastic view complete with some great staging items, the concrete literally begged for a makeover equal to its beautiful surroundings.


Concrete ready for decorative concrete makeover


Cracked and rough concrete and an outdoor setting are perfect candidates for a flagstone pattern, so Derek and Jared got busy.




Concrete stained with Concrete Resurrection RAC stain


Rather than repairing the cracks, the guys decided to use them, and to draw in even more in a natural looking flagstone design. Grout lines were hand stained with a brush to make the design pop.

Decorative concrete flagstone



Jared and Derek applied Concrete Resurrection RAC stains in Western Saddle, Brownstone and Black Walnut to get the lovely shades of brown that give the stones look a realistic look.



Concrete Revival decorative concrete slab


The customers were well pleased, and it’s easy to understand why when viewing photos of the finished job.




Flagstone pattern on concrete



Engrave-A-Crete salutes you, Derek and Jared, for excellent work in the decorative concrete industry!


To see more awesome projects by Concrete Revival, visit and like their Facebook page.

To learn more about Concrete Resurrection stains, sealers and products, go to

Concrete Revival posted this response to this blog post:

Always a pleasure seeing our work posted to the Engrave-A-Crete Facebook page! We are truly grateful to be showcased on their site. The project featured in their latest blog “Down by the River” was a unique project for us. This exhausted slab was formerly the base pad for a grain bin and had seen better days. The concrete had some major cracks and distressed features that lent themselves to a flagstone appearance. Our clients were very happy with the end product and planned to use it as a patio space. Thanks for being such strong supporters of Concrete Revival; we wouldn’t here here with out Engrave-A-Crete!


What to do? Decorative Concrete Flagstone!

Wes Fitzpatrick driveway cropA decorative concrete engraving dilemma…What to do, what to do?

Your customers want a beautiful decorative concrete installation on their terribly used and abused driveway.  Not only do they want it lovely, they want it for a minimal cost.  What’s your best option for meeting their needs while earning a fair profit?

Engrave-A-Crete CEO, Darrel Adamson, responds to the situation based on the photo of tired, ugly concrete above.

“Engrave flagstone!” Adamson says. “It would look good now and in the long term. The concrete looks eroded, but that texture will compliment the look of flagstone.”

Often with old concrete there’s the issue of patches that may or may not have been correctly installed.  Or, the concrete itself may be failing. Flagstone is still a good choice.

“If something goes wrong,” Adamson says, “ for instance, if some of the existing skim coat patches delaminate, it would be simple to recolor that area and it would be part of the existing stone,  or it could  become a new stone itself.”

Surface Prep

Properly preparing the surface is essential to the success of every decorative concrete installation, and it’s especially vital on a surface such as this one.

“Test for delamination of the patches AND the un-patched areas. NO acid etching. It is old. Pressure wash thoroughly,” Adamson says.


Next comes the issue of whether to use acid based or water based stain. Would acid stain work on concrete ?

“Make it MULTIPLE Concrete Resurrection colors BEFORE engraving it,” Adamson says. “Spray a little color here and a little there and everywhere.

“Acid stain (RAC) may not work well, but could be worth a test area. Water reducible concentrate(WRC) applied sparingly would look good. Possibly a combo of RAC and WRC stains with the acid stain applied first and then neutralized, plus more pressure cleaning of the acid stain residual. Then, spray on WRC in selected areas.”


“It looks like some of the rather large chunks have been replaced,” Adamson continues. “Turn them into smaller elongated stones. Make the cracks into mortar/grout lines and engrave more stone shapes off of those cracks.”

Once you’re finished and the surface is clean again, apply Concrete Resurrection sealer so the job lasts.

k-crete-pro-pack_1The Engrave-A-Crete KaleidoCrete system is ideal for engraving  flagstone patterns. Use the re-positionable and reversible templates and vary the sizes of the stones as desired to fit the space you have, and to disguise cracks and imperfections in the surface of the concrete.

Decorative Concrete & Radiant In-Floor Heating

Radiant in-floor heating systems are becoming increasingly popular due to the comfort they provide, their green benefits and the decreased energy consumption required to keep a living space comfortable.   Using Concrete Resurrection Reactive Acid Chemical stain on a concrete surface that contains in-floor heating may raise some questions for the decorative concrete flooring installer.radiant in-floor heating effect on acid stain

Chris Mirabal, Tech Support at Engrave-a-Crete, gives a few pointers for successful acid stain jobs on concrete that contains radiant heat coils.

If the heat is on:

  • Set the thermostat at 65 degrees (or a comfortable working temperature) a few days ahead of time so the slab and surroundings are a fairly constant temperature.  Leave the thermostat set during the entire staining/sealing process. By doing so, you are controlling the variables of temperature and humidity.
  •  Prep the surface as usual.
  • Be certain the floor is damp (with no puddles) when you apply the acid stain. Be aware that the radiant heat source within the concrete zaps the moisture out of it pretty quickly. You will be applying stain to a porous surface that may dry before the chemicals in the stain have time to react with those in the concrete.

If the heat is off during the entire installation time, follow normal acid staining procedures.

How to Prep a Concrete Floor for Acid Staining

Basement Floor PrepFloor prep prior to acid staining a concrete floor isn’t exactly fun. But, it is, without question, the most important step toward the success of the project. Take the time to do it right! You’ll be glad you did.

Why is floor prep so important? The answer is simple – any contaminants on the concrete’s surface may inhibit the penetration of acid stain.

Here are 5 basic steps toward preparing your concrete to accept acid stain so you get the rich, beautiful floor you’re looking for.

1.  Evaluate the Surface

Be sure the concrete has cured for at least 30 days, or the stain and/or sealer may fail.

Look for damage and wear that may need to be repaired. Minor cracks and defects often add to the beauty of stained concrete and should be left as is. Use a filler for major repairs (we’ll address this in another post), but remember that the filler will accept stain differently than the concrete around it, affecting the color saturation where it’s applied.

Look for oil stains, paint splatters, carpet glue and any other substances that may require special treatment for complete removal.

Sprinkle water in several places. If it beads and the color of the concrete does not change, then a barrier (usually sealer) is present and must be removed during the floor prep process.

2. Gather Supplies

Once floor prep begins it is a continuous process, so have your supplies ready and easily accessible. Supplies include:

floor machine with black pad and/or sanding screen, wet vacuum, sanding sponges, floor and razor scrapers, margin trowel, mop and bucket, safety items including, but not limited to, safety glasses, protective clothing, and non-slip footwear

Concrete Resurrection Paint and Sealer Remover

Concrete Resurrection Degreaser

3. Clean

Cordon off the area for the safety of others and to keep additional contaminants from ending up on the surface once it’s cleaned.

Remove all loose debris by sweeping/vacuuming the entire floor.

Remove sealer and contaminants using Concrete Resurrection Paint and Sealer Remover as directed. See our online video Decorative Concrete Preparation Part 2 for more information on removing contaminants and sealers.

4. Scrub

Wet a section of the floor and use a rotary scrubbing machine with a black pad or sanding screen. Work in small sections, and be sure to use only the amount of water you can control.

It’s advisable to have a buddy vacuum and squeegee up the water and slurry as you scrub. Do not allow slurry to dry on the floor as it will not come up with mopping and will act as a barrier to stain and/or sealer penetration.

If you used Paint and Sealer Remover on the surface, be sure to follow up with Concrete Resurrection Degreaser during the scrubbing phase of floor prep to eliminate the residue left by the Remover.

See our online video 10 Critical Steps for Concrete Staining and Engraving for more information.

5.  Mop

Go over the area thoroughly with a wet mop and plenty of fresh, clean water.

Allow the surface to dry completely before proceeding with acid staining.

Floor prep is hard work, it’s messy, and it takes some time, but it’s worth the effort to be sure your decorative concrete installation lasts.