Why did my Gray Stone turn Brown after sealing it, and how do remove it?


I just had a professional install natural cut stone on the floor of my clients new shower. After it was sealed, the gray I selected, turned brown. It does not coordinate with the white and grey Carrara marble walls. Tearing it out would be a nightmare! I have read that stripping and staining porous stone is an option. questions:

What method do you recommend to change the color of the stone to grey?

Will striping and staining the floor lead to potential problems being that it is the floor of the shower.

Are there specific products you would recommend? Please advise. Designer In Distress.


ANSWER - Depending on what type of sealer you applied, it can enhance the natural color of the stone.   So perhaps the installed stone unsealed, or perhaps the sample that you originally selected, appeared to be gray in color, but in fact had a brown undertone.  The sealer may have enhanced the natural stone color bringing out the brownish undertones.  Natural stone is just that; natural.  So its inherit qualities will vary from shipment to shipment and from stone to stone.

You could have used a type of penetrating sealer that doesn't enhance the natural stone color and that would have given it more a natural look.  You should have had a mock-up made of the stone and sealed it to see the outcome, before sealing the entire floor.  In fact, the architect should have specified a mock-up prior to the tile installation using the specified and supplied tile, grout, and sealer that was to be used.  That way there are no false expectations of what you get, and you then have a chance to make adjustments.

You can strip the sealer from a natural stone.  It is best to you the stripper recommended by the manufacturer of the sealer that was used.  Otherwise you have to do some trial and error by experimenting with various strippers to make sure it works.

It is possible to stain porous stones with concrete stains, although it isn't normally done.   You do need to remove the sealer first so the stone is porous.  The stone needs to be very porous in order to accept a stain.  Dense stones don't stain easily.

Whatever approach you take, you need to test a small area out of the way to verify you are going to get acceptable results, before you apply it to the entire floor.

You can also hire an experienced professional natural stone restoration company who has experience working with situations such as this, which is what I would recommend.  Make make sure you check out the stone restoration's references.

26 thoughts on “Why did my Gray Stone turn Brown after sealing it, and how do remove it?

  1. Maggie says:

    It happened to us too after spending thousands on the stones. The sealer actually painted the stone brown and took all the natural Sparkles out of the stone. I am really pissed that the tile company didn’t know about this. They just told us that it gives it a wet look.

    • Donato Pompo says:

      A true enhancer sealer that gives a wet look will normally darken and enhance any metallic minerals in the stone. It should not coat over the stone that would cover the natural features of the stone. Maybe what you applied was not a true stone enhancer…

  2. Wendy Conway says:

    Same here! Very annoyed the contractor didn’t ask about whether to use an ‘enhancing’ sealer. I did not know there was another option.

    • Donato Pompo says:

      On one hand people sometimes do not appreciate when they are approached with up-sell suggestions, but on the other hand giving the customer a choice avoids false expectations and gives them the opportunity for added value. Of course, not all up-sell options have value, so you have to scrutinize the options in making a decision.

      • Natalie Nelson says:

        What type of sealant won’t change the color of the limestone? I am about to install a light greige color and do not want it turning brown.

        • Donato Pompo says:

          I assume you mean a liquid sealer and not a caulking sealant. Sealants that are used for caulking can stain stone, so you have to be sure to use one that that is specifically for natural stone. Even then the manufacturer states that you should test it out to make sure the sealant will not stain it.

          Normally penetrating types of sealers and sealers that are promoted as Natural Sealers are not suppose to significantly change the appearance of the stone. Here again, you should test out the sealer that you want to use on your stone by applying it on uninstall piece of the stone or in an inconspicuous spot on your installed limestone to help ensure you will be satisfied with the outcome.

  3. Donna Marburger says:

    We had a new shower installed and the stones on the floor were white and shades of gray. The turned light and dark brown. The stones are limestone and were purchased at Home Depot and they seem to not want to stand behind their product. Do you have suggestions to fix this problem. My shower tile and the entire bathroom is gray and now I have a brown floor. Any advice is most helpful. Thank you for your attention to my request.

    • Donato Pompo says:

      If the limestone tiles changed color after they were installed on the shower floor it is either because an enhancer sealer was applied that gave the stones a wet look and enhanced the natural color of the stone.

      Or if the mortar bed to which the stones are attached to is retaining moisture and can’t dry out that can give the stones a wet look that enhances the underlying colors or tones of the limestone. If the installer didn’t use a waterproof membrane over the surface of the mortar bed or if the underlying drain at the waterproof membrane had its weep holes plugged and not protected, then the water can’t drain away through the weep holes. This will cause the mortar bed to retain moisture that will migrate into the stone giving the limestone a wet look that can appear substantially different from when the stone is dry.

  4. R Lupo says:

    I don’t see any remedy given for the limestone tiles that went from gray to brown. Let’s say the shower pan and mortar, weep hole are done correctly and they are not the issue. The issue is the color enhancing sealer and how to remove it. Looking forward to your response.

    • Donato Pompo says:

      You go to the sealer manufacturer and ask what kind of sealer stripper to use. Now if the sealer penetrated a ways then the stripper might not to it completely. You can then grind and hone the surface of the limestone to remove it.

      • R Lupo says:

        Thank you. I was considering using Smith’s Stain after removal. I am a pro painter and have experience with Smith Stain. Could I skip the stripper step and just grind and then possibly use the Smith’s?

        • Donato Pompo says:

          You could just grind. I would test it out first on a sample to make sure you will be satisfied with the result.

          It is not normal or covered by natural stone industry standards to stain a natural stone. Geologically limestone has 3 classifications: low density, medium density and high density. So the porosity will vary depending on the type of stone you have, so if you attempt to stain it you will have to experiment. There is no way to know how long it will last or how it will perform.

      • Tahnee says:

        So I have the same issue where sealer is causing my mostly white limestone to turn more brown shades. I tried both a water based and a solvent based impregnator sealer prior to installation and BOTH brought out the brown tones (like others I like the white and. Greige pre sealer). If I can strip the sealer at this point what can I do to protect the limestone as NO ONE says leave it un sealed. Should I leave sealer in to protect the stone and then still grind and hone it? The store did also have some honed and I didn’t choose that because it looked more creamy which is how mine has now turned out

        • Donato Pompo says:

          Natural stone is just that natural so the color you get after sealing the stone is just enhancing its inherent natural color.

          You don’t have to seal the stone. Some geologists believe that by sealing the stone it doesn’t breath as it should.

          If you have a low density limestone that means it is very absorbing then you should have a sealer to minimize the risks of staining if something is spilled on it. There are penetrating sealers that don’t enhance the color and doesn’t change the color. Miracle 511 Impregnator normally doesn’t affect the appearance or Prosoco Natural Stone Sealer. For links to their websites and other sealers go to: https://ctasc.com/category/resources/cleaners-sealers/
          To be sure test a small area to make sure it is acceptable.

  5. Laura Jenkins says:

    Hello, we had a paver patio installed in June. We have white limestone on the seating surfaces around the firepit. After the sealant was applied, the limestone is now beige/brown. I have contacted my contractor who stated that the color will fade back to a lighter tone and is more drastic soon after the sealant. He states that the after the winter, you will see the lighter color coming out in the limestone after being in the elements. What options do we have? I am not happy with the beige/brown color as our patio is shades of gray with white accents. Thank you.

    • Donato Pompo says:

      Chances are your contractor applied an enhancing sealer to the limestone that gives it a somewhat wet look. Or many he used a surface sealer that tends to darken the tile and give it a sheen. On some stones like sandstone the enhancing sealers brings out the color and is desirable. The contractor should have used a penetrating sealer that would not have altered the color of the stone.

      You can contact the manufacturer of the sealer used and ask what type of stripper to use for removing the sealer and that might work, but you have to be careful so you don’t end up with a worst problem. Always test in an out of the way spot to make sure you will be satisfied with the results.

      • Georgia Phillips says:

        Hi Donato. My quartzite (white) stone is developing brown spots throughout. We haven’t spilled or stained it in any way. Sunlight hits it where the brown marks have appeared. I can email you pics if you’re willing to help me trouble shoot the cause and solution.

        • Donato Pompo says:

          If it is a true quartzite it is very dense and resistant to staining and etching. All natural stones contain various minerals and iron sulfide (pyrite) which can develop a brownish-rust-like stain. The direct sun can perpetuate oxidation that can lead to stains.

          I have seen some professionals use a phosphoric acid solution to remove stains similar to this in other types of stone, but I would not do this on your own without professional help to make sure you don’t make things worst.

          On the other hand, it is natural stone with natural weathering characteristics so you can just live with it and its intrinsic beauty.

  6. Carla Lazarus says:

    Hi. I have grey slate stone outside that has gone orange after my tiler cleaned them using low pressured water and acid wash (hydraulic) and he then used a penetrating sealer. They are not new tiles and came with the house we bought last year. They were in good condition. They also have increased black spots but the new orange hue is the most concerning part. The tiles go around the pool as well and along the edges of the pool there are orange marks as if one of the products was orange and dropped down towards the water. Do you know what could have caused this? He is trying to fix it but has no idea why this has happened. From a quick read online I have seen that hydraulic acid can be a problem on stone? Many thanks

    • Donato Pompo says:

      I assume you mean hydrochloric acid, which is an undiluted acid with a pH of 1 or 2. Muriatic acid is about a 15% diluted hydrochloric acid, which is normally used in swimming pools. It too has a pH of 1 or 2.

      You should never use hydrochloric or muriatic acid on any tile or stone. It is too corrosive and can cause damages to the tile or stone.

      Slate naturally contains pyrite which is a Ferrous Sulfide (FeS2) mineral. It will react with the acid oxidizing the metal causing rust stains. Your slate might be a natural stone that looks like slate but has different physical properties. Once of these sub categories is Phyllite, which is know to have large cubes or crystals of pyrite that quickly oxidize and bleed ugly iron stains.

      So assuming that these are inorganic rust stains then there are poultices with diatomaceous earth and a commercially available rust removers which is a acidic material. You have to experiment to see what will work. You should hire a professional stone restoration company who has experience with your type of situation who might have a solution.

  7. Jeff Carbine says:

    It’s awesome that this article talked about depending on the type of sealer you choose, the natural hue of the stone can be enhanced. I’m glad that you explain it thoroughly and now it makes more sense I should pick the right sealer so that the color would enhance. You did a great job of explaining stone sealing coating.

    • Donato Pompo says:

      Limestone is categorized in the three different classifications per ASTM C568. There is low density limestone, medium density limestone and high density limestone. Each category has different levels of absorption and density. Most limestones tend to fall in the medium density to high density classification.

      So first of all your limestone is limited in being able to absorb a stain. Water based stains will tend to blead when subjected to water. There are sealers that come in stain colors, but depending on the stone absorption it might not absorb much. Plus sealers don’t last that long outside, so you have reapply often.

      I would never stain a natural stone. It isn’t recommended by the industry. You can get an enhancing sealer that tends to give the stone a wet look that will enhance the features of the stone. That would be your best bet.

  8. SD says:


    We had a natural stone tile placed in our master bedroom floor with light gray grout. The contractor sealed it as well (I don’t know what kind of sealant). After it was sealed, I’ve noticed brown spots all over the tile. Is there anything I can do at this point to get rid of the brown spots?

    • Donato Pompo says:

      Depends on what kind of natural stone you have. Generally speaking natural stone can be restored like new because it can be ground down and repolished since it is the same material from top to bottom, more or less.

      The question is if the staining is coming from the surface or is it coming from under the tile. Surface stains are more likely able to be removed. You want to know what caused the stain so you can prevent it from reoccurring or from getting worst. So you don’t want to just treat the symptom of the problem, you want to fix the problem.

      Most stone contain minerals that forms of salt. Some minerals are metal such as iron sulfide which is common in marble. Some times if the stone is subjected to moisture it can cause a rust-like stain.

      Best bet is to hire a professional stone restoration company who has a lot of experience at restoring natural stone floors.

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