Acid Stain/Acrylic Sealer Problem...Efflorescence?

17 replies [Last post]

We poured this residential, interior slab 6 months before we colored and sealed it.  It has radiant heat Pex tubing in it and a vapor barrier underneath.  We scrubbed it with a floor machine and moped and vacuumed it with fresh water before we allowed it to dry and stained it with an acid stain.  The surface was then moped with a solution of vinegar first and then with fresh water several times. Two coats of an Acrylic sealer was then applied.  We had a little trouble with lines so we used some xylene to level it.  A few days later some cloudy areas began appearing.  Over a couple weeks most of the floor was discolored and rough looking.  Most of it is a dry, rough looking gray.  Some of it even looks a dark brown or black with the texture of rust on metal.

What is it?

What can I do?

Dr J's picture
Dr J
More info

Was the acrylic water based? What kind of test did you do to verify the acid stain was neutralized completely? The answers will help identify the issue.

The sealer was xylene based

The sealer was xylene based acrylic.

We did no tests before sealing. 

Dr J's picture
Dr J

That would then lead me to think the issue is with the acid stain not being completely neutralized. I kinda think that removing the sealer and then neutralizing the floor with ammonia , rinsing rinsing and rinsing will get you a prepared surface. Do a test spot to verify.

Lindy A.'s picture
Lindy A.
I agree with Dr J.

I agree with Dr J.

How do I remove the

How do I remove the sealer?

Will I need to restain?

And thank you both very much for your time and help.

Why did you mop the floor

Why did you mop the floor with vinegar??? For some reason, people think they need to neutralize the floor with vinegar. Vinegar is an acid!!!

you are going to have to strip the sealer, clean and properly neutralize the floor (10 parts water to 1 part ammonia, or baking soda and water solution), let the floor dry for approx. 24 hrs. and then reseal.


How do I strip xylene acrylic sealer

How do I strip the xylene acrylic sealer?

Will I need to restain it?



Stripping Xylene based Acrylic sealer

How do I strip the xylene based acrylic sealer so I can properly neutralize the acid stain under it?

Dr J's picture
Dr J
check the archives

that procedure has been discussed to death on this forums ...There are several ways,.. none easy. that is why it  is so critical to do all the checks and balances on a floor before sealing. Testing an area with a sealer is essetial. You have your work cut out for you my friend.

Chris K
removing Xylene Acrylic sealer

Try a small test area maybe 5x5 or 10x10 , lay out some xylene and after several miniutes start rolling back and forth with a roller until the xylene starts to get thicker.

Lay out some more Xylene and repeat rolling to smooth out (try not to let the material dryout) If there is excess material you may need to squeegee excess into a pile and pick up with dust pan or shovel.

Let surface dry completely and see if white areas reappear. Step outside and enjoy your buzz, just kidding, use in a well vented area with a proper respirator.


Thank you both. Sounds like lots of fun. I don't know why my instructions tell me to use vinegar after staining?
Thanks again.

Lindy A.'s picture
Lindy A.
Are people currently living

Are people currently living in this house that you intend to use xylene process (or other solvent based, fuming, hazardous alternative to strip off the solvent based acrylic sealer.  You know there are environmentally friendly/safe alterntaives for stripping of sealers.

Yes. It is occupied, but

Yes. It is occupied, but will be vacant when we do any floor work.

Chris K
Xylene sealers

Good point as far as keeping people away while using the xylene, pets are also affected by the xylene.

My dog had a seisure at night, the day I applied multiple coats of a xylene sealer on my garage floor.

She was sleeping in the bedroom above the garage and I knew the smell was strong but did not think it was that bad. 

Some animals as well as some humans are more sensitive to these strong odors.


Be safe

trucrete's picture

You say that after you cleaned the floor, you let it dry and then stained it.  2 things...

first, just mopping and rinsing the floor after staining is not enough to properly remove all of the residue.  Even though this method is all over youtube and in every discussion forum, it is not enough. 

That is why acid stained floors look like they lose their color so fast.  The residue gets sealed in and is just a loose debris at that point on top of a slab and wears away quickly. 

I have heard people say that they remove the color if they scrub with a rotary scrubber.  That may be the case if the slab is soft but 90% of the time what they think is color, is actually residue.  I have done too many floors to be convinced that elbow grease and a mop is enough to remove 100% of the residue.

so, in the future, use a rotary floor scrubber to clean residue.  Do the white glove test.  Scrub and rinse until you can wipe the surface with a white cloth and it remains clean.  You may not get it to stay completely white but nothing more than just a faint stain color should be visible on the cloth prior to sealing.

Secondly, how long after you mopped and rinsed the slab after staining did it sit prior to sealing and what were the conditions? 

All basic directions say 24 hours...well if you are venting the moisture outside and it is 95% humidity for example, 24 hours will not be adequate. 

The caulked area in the door way and the crack have the least whitening and would have been able to still breathe after the sealer was applied.  The rest of the floor would not.

It looks like moisture to me and the slab getting darker and almost black in areas is what happens in the concrete when moisture is trapped in the slab.  Whitening is moisture trapped between the concrete and sealer.

Brush some xylene heavy on the floor about 12" x 12" heavily and allow to dry.  Check clarity.  Maybe do again if it is not clear.  Use all precautions doing this inside( I am against solvent based acrylic in any interior situation).

Let me know if this clears it out and we can go from there.

Lindy A.'s picture
Lindy A.
I hope that all those reading

I hope that all those reading this post get the picture in relation of the use of solvents on indoor surface that typically lack adequate ventilation, as well a being toxic, hazardous, and fuming.  There are alternatives (be it strippers or sealers/coatings) that are non-hazardous/applicator friendly/environmentally safe. As pointed out in above post, "people and pets" can be effected by lingering fumes that can enter into air ducts (and filters) or anything in close proximity (drapes, furniture, carpet, etc in close or adjoining rooms).   Exterior surfaces are a matter of preference as to whether solvent based strippers or stripping methods that use xylene, sealers, coatings, etc are applied; however, when it comes to interior floors I steer clear of them.

As far as substrate moisture, I highly recommend vapor emission testing ... I'm NOT referring to taping down a sheet of plastic (IMO this is more of a dog and pony show; doesn't tell the "whole story").  At the very least calcium chloride tests should be performed (which depending on the size area can take more than 1); better yet is a moisture meter; provides immediate results, with the probe type being the best as to ascertaining what is going on within the concrete itself.  Keep in mind, just because test results are within acceptible limits when you did the job doesn't mean that condtions may not change at some point of time in the future (such as during long periods of rainfall that saturates the ground (this can wick under slab then attempt to rise up through it, especially if the lay of the land around the permeter of the slab does not allow adequate drainage/run off away from interior or exterior concrete. 

Also suggest that testing the surface prior to staining in relation to acquire PH factor of the concrete be done (ie: will provide a akalinity reading; it not within neutral range will need to scrub/neutralize/rinse again).  There are PH pencils for this purpose ... allow the surface to dry (at least the top mils), wet the surface with distilled water (regular tap water can give you misleading or false results) only to the point that the slab is wet (not puddling distilled water), then mark with the PH pencil ((color readings on side of pencil will have numbers under each color, PH in 7.5 range is neutral).

trucrete's picture
a few thoughts

As Lindy mentioned above, testing for moisture prior to the installation of a coating is a good idea.  Any snap shot of the concretes moisture content is just that, a snap shot. 

The most accurate testing method for moisture is moisture movement which is what the 60 to 72 hour test kits do.  You are to test several locations.  Grind a 2' x 2' area and leave for 24 hours.  Weigh the test and document.  Tape down the test kit and leave for 60 - 72 hours and weigh again. 

This will give you the moisture content of the slab over a period of time and is much more accurate.  However, as Lindy said above things happen long after the job is finished that are beyond your control.  Like a basement flooding.

In Maryland over the last year, we have been hit with an earthquake and a hurricane.  This affects concrete in ways sometimes not visible until the problem itself shows its face.

I do believe that taping down a plastic sheet for 16 to 24 hours will give you a really good idea of the moisture content at the time of the test.  This sometimes is all you have time for because as all of you know by the time the floor is ready to be done, they are behind in the schedule and over budget and time or money will not allow the adequate testing.

We can say that you should not do the job at that point but we need to eat.  No matter how much testing you do, you will not catch everything.  I saw surfactant cause bubbles in an epoxy floor 2 years after it was applied.  Cut the bubble with a razor and an oily substance came out.  The building was a warehouse for chemicals used to make soap for 80 years and after 2 years it decided to show its face.  No test for that.

Moisture testing will not help in this situation and can not really be done with the floor coated anyhow so determining if moisture is the issue is done the way I described above.

Have yo had a chance to do any testing on the sealer yet?