Bateig Azul White Discoloration

[HCEB]

Hi

We had a new bath professionally tiled with Bateig Azul limestone about a year ago. The steam shower which has 12 x 24, 5/8" tiles sealed with several coats of Porous Plus on the walls has many tiles with a white "haze" type discoloration. The haze appears to be primarily where the mud dabs were placed to install the tile. We used Laticrete multi-purpose thin set, gray over wonderboard. The steam has only been used 3 times.
We do not think the problem is efflorescence because it is not at the joints, but in the middle of the tiles.

We tried polishing a tile with various grades of grit, then applied a sealer coat.
The haze disappeared at first, but came back within an hour.

We also did a Galil Gold limestone shower at the same time with no problems.

Has anyone found a solution for this problem ? My opinion is that it is a chemical reaction with the Laticrete, but I dont know for sure nor how to fix it without re-installing the walls.

Thanks, Howard

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[GraniteGirl]

Limestones are tricky suckers when it comes to moist enviros. Any way you can post pictures?

What is the construction of the shower wall?

[HCEB]

Hi

I love your "rock" comment!

The walls are new 2 x 6 studs, covered with wonderboard. The tile was installed with Laticrete. The back of the tile was buttured (?), then dabs of Laticrete were applied to hold it in place. The installer told me he could not apply an even coat and press against the wall because the tile was too big, 12 x 24 and would not stay even on the wall (my words).
I spoke to a tech rep at Laticrete a little while ago. He said he had not heard of the problem before, but would ask a local rep to do a siste visit.
I'll take some photos then.

Howard

[GraniteGirl]

You make no mention of a vapor barrier. Did you apply any kind of membrane eg Kerdi or Redguard?

Your problem might have something to do with vapor transmission through the tile.

[HCEB]

Hi Adriana,

Thanks. I asked the same question. No there is no vapor barrier, but these are interior walls. Of course there is plumbing for the shower in one of the walls, but both have the same problem

Howard

[GraniteGirl]

Your problem is caused by lack of a vapor barrier and it will probably be the least of your worries - with it being a steam shower and all.

I will have to go look up the explanation, but your problem has been seen in limestone used in wet environs where there is a certain amount of vapor transmission and no vapor barrier.

[GraniteGirl]

What you have there is "Alkali Staining" or "Halo Staining" - a situation that is terminal (i.e. not fixable)

This happens when vapor moves through an alkaline substance (in your case the mortar), dissolving the minerals in it and migrating up and through the tile. The vapor evaporates (sealers are vapor permeable, allowing the stone to "breathe" as it should) and leaves behind the salts in the limestone tile, causing discoloration.

The application of a moisture barrier prevents this. Some folks are of the opinion that presealing the backs of the limestone tile would also prevent moisture from migration through the tile and so eliminate this problem too.

As I have mentioned previously, the fact that you have a steam shower (regardless if it is interior walls) without adequate waterproofing in the construction, dooms you to troubles way bigger than just stained tile.

[HCEB]

Adriana,

Thank you. I forgot to mention it before because my recent investigations didnt seem to make it important, but the well water in the house had a very low pH until recently when the owners had it corrected.
I initially thought that might be part of the problem, but no one else seemed to think it was significant. The pH is now near neutral.
Also the owner has only used the steam 3 times in over a year.

If we remove the tiles, install a vapor barrier, and then replace them with same, but new ones, do you think we can seal them front, back and sides to prevent re-occurance ? What sealer would you recommend, since some allow "breathing" ?

My tile re-finisher has suggested a test with a poulpice application. I am dubious because even if it works, the stains may come back. But it costs little to try.

Howard

[Davestone]

You've simply got the wrong stone for a steam shower i'm afraid,some limestones are more sensitive, and a gray thinset dabbed on the back isn't helping,white would have been better, but probably not perfect,as it still contains alkali, if that is what's happening.I've seen many installs have shadows of the setting material show through.Maybe Adraina has some input.

[GraniteGirl]

I have to concur with Dave on this one. The stone you have there is not really suitable for use in a shower. I know it has been done before and I know that there are people happy with the results and yada yada yada...

Bottom line is you need something that will stand up to being in a shower and taking a certain amount of abuse. A honed travertine will be a much better choice for use in a shower environment. The stone was formed in hot springs with water action, is denser and will not require near the babying that limestone (a simple sedimentary stone) requires.

All personal hygiene products have a certain amount of acid in them, plus you will have soap scum and dirt that would need to be cleaned up. Limestone just plain will not stand up well to this.

My 0.02

[HCEB]

Adriana and Dave, thank you very much for your insight and responses.

When I reviewed your comments with my installer, he reminded me that we had installed Denshield over the wonderboard. This was done as a means of meeting the shower design and make the bottom 8' of the tile stand proud of a detail near the top of the walls.

Needless to say we have a problem to resolve for the owners. In retrospect I wish the stone vendor, a respected major metropolitan supplier, would have warned us away from this product for this application. If nothing else they knew or should have known this is a product that apparently should be used in dry locations.

Howard