Acid staining and concrete curing agents

Acid staining and concrete curing agents


Are you planning on pouring a concrete floor and doing acid staining on it? Or maybe you want to get more educated on acid staining and things that are worthy of notice?

If you’re planning on pouring a new concrete slab and intend to get an acid stain on it once it’s done, there is this one thing you should know about. Using concrete curing agents on the concrete can potentially ruin your acid staining project if not taken into consideration.

Concrete curing agents are used by concrete contractors and general contractors to hold the moisture in the slab during the curing process. Usually, this will help the concrete to reach its maximum strength so it’s not bad in that sense, but for staining it is unwanted.

If you know how to acid stain concrete, you most likely will know how curing agents affect the process.

Curing agents will resist the stain

The problem with this when acid staining the concrete is that the curing agent acts as a resist and will not let the stain penetrate the surface of the concrete and introduce the metal salts to the free lime in the concrete. This is what creates the color and when it’s not happening it leads to the color discrepancy.

While most of the time this not done intentionally to screw up your project it is a big pain in the butt to remove and honestly less work for you would be a different curing process. Which would mean more work to contractors.

Concrete curing agents might not disappear as fast as promised

The general contractors and maybe even the concrete contractor will tell you that the curing agent will dissipate over the first few weeks and that you should not worry about it. It’s not really the proper truth and they should know it too if they are professionals.

What you are left with is at times a spotty finish and for the most part a floor that gives you that “industrial” eclectic look, it just really didn’t take the stain.

There have been cases people have called and asked for other professionals to come and take a look at a floor that their “professional acid stainer” told them was a good job. The stain flat out didn’t take and if they would have done a simple water test on the concrete they might have known they were in over their head.

Note: Simplest water test is to tape a plastic sheet to the concrete for 48 hours or place a rubber mat on it. After the time is over take it off and feel the surface of the plastic or rubber and if it’s moist, you know there is moisture that can be measured in the slab as well.

If the top of the plastic is moist, the room is moist and you should dry the room. Anyway, these are things that are easy to measure.

You shouldn’t compromise in your search for perfect floor

Now while many loft owners are looking for this look it just really isn’t everyone’s cup of tea and the result we don’t expect is a failure, right? First of all, if you want a deep rich marbleized floor that rivals a polished stone floor and acid staining can achieve that given the right variables, it should be achieved.

So if you have any control over the project from the beginning make sure you specify that the concrete has no curing agent put on it and that the concrete should be wet cured. There is also the option for using curing paper and plastic indoors if the acid stain is planned.

After that, it’s just a matter of patiently waiting that the moisture level in the concrete is proper for the acid stain. As stated before, too much water might lead to an unsightly color discrepancy on the final surface that we don’t want.

The general contractor or the concrete contractor may disagree on different levels and threaten to charge more but it’s worth it and should not be any problem if agreed on before the job. Besides, you can always find another contractor that will cooperate with you as it just requires them to wet the concrete daily for the first few days. It’s not really that hard.

If you’re curious about doing this yourself, here are some steps to acid staining concrete.

Using the curing agent for concrete is not advisable here

In case curing agent has been used already

If you do have a curing agent on the concrete you will need to remove it to get a properly stained concrete floor. There are several products on the market such as Take-it-Off, Removal, Citrus Peel, etc. that will do the job.

The only crucial thing you need to worry about is to scrub the floor thoroughly and continuously for an hour or so (with a very stiff-bristled broom) to allow the chemicals to get into the curing agent and work on emulsifying the curing agent.

At this point, you may want to introduce a floor maintainer and a black, green, or blue pad to get the product up and then introduce water to the mix and shop vacuum the floor, and dispose of it properly.

Repeat the floor maintainer process two or three more times until you can pass a “white glove” test on the floor. A white terry cloth towel will do also, you just want to be sure that the job is done for sure.

Otherwise, when you stain the floor you just may see footprints in the floor as you stain. You’ll stand there and say “Where did those come from?”. That would be the leftover residue ruining your day.


No matter if your pouring the slab yourself or using contractors if you’re staining with acid avoid using concrete curing agents. Some say that wet curing causes some color variations as well, but I think those are lesser evils than the ones caused by curing agents.

You should know how to prep concrete for acid staining and also how to neutralize the acid stain before sealing. With all of this knowledge, you’re off to a good start.

After that, get yourself familiar with staining and different staining textures you might want to try. After you feel like you’re ready, still do a test on some concrete pad or something else. After that, you’re ready to go.

It’s mostly a matter of choice to be prepared really so it shouldn’t be a problem for anyone. Doing it like this will let you have a floor that you can plan and work for without random elements affecting the end result.