This is exactly what's happening with the travertine patio I recently looked at. But in addition much of the surface is crumbling in spots and generally mildly spalling. It is under cover, but I am sure it is getting its fair share of the elements. They may have had the patio uncovered through the winter, now that i think about it. I researched Prosoco' two step
HCT (HTC?) process followed by their limestone sealer (actually a crystallizer as far as I can tell after talking to Prosoco) recommended in another post. I am always very suspicious of claims by sealer manufacturers and it would either be too time consuming or just to difficult to simulate a test scenario. I guess the way to go is to always state that the area will need to be realed within a short period of time and offer no particular warranty. I just looked at a 75000 sf warehouse where they coated the brick floor with epoxy. After less than a fee months the epoxy is delaninating all over. I'm just glad I'm not the guy who made the decision to cost the floor. The whole coating/sealer/impregnating area gives me the creeps.

On Thursday, June 7, 2012, John Freitag <jfreitag@thestoneandtileschool.com> wrote:
> I normally tell customers on warm climates like Florida and California that exterior stones need to be cleaned and sealed at least every 12 to 18 months
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> John E Freitag
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> Director
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> The Stone & Tile School
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> Office 407-567-7652
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> Cell 407-615-0134
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> jfreitag@thestoneandtileschool.com
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> www.thestoneandtileschool.com
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> From: Randy Frye [mailto:rfrye@comcast.net]
> Sent: Thursday, June 07, 2012 6:33 AM
> To: Restoration and Maintenance
> Subject: RE: [sccpartners] Dusting Marble
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> Hi Mike
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> I see this problem all the time in florida. I let people know to expect it. I let them know it oxidizes from being exposed to the different elements outside. I personally think most of the oxidization comes from the UV Rays. Just like a cars paint job does over time setting outside. You might ask if the ever use chlorine to kill mold, that will intensify oxidation. 
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> My last pool area I did paid $2,200.00. I decided to offer, if done within 1 year the cost would be $1,500.00. They accepted this offer.  I will continue to make these offers because it will be a problem they will need to overcome in the future and I can be the solution, They give me the problem- I give them a discount its a win win situation.
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>  Unless they opt to expand the roof over the whole area. :(
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> On Jun 4, 2012, at 9:43 PM, Mike Marsoun wrote:
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> Sorry, no photos but I looked at a job I did a few months ago (flatten to 800ao hone) with a very dense marble from Greece that is (for lack of a better phrase) “oxidized”. All areas that are not under roof are turning light, as it if it were etched. When it is rubbed with a finger there is a chalk residue. This residue washes off but to fully remove it takes some abrasive action, I did a small sample with a 800 grit Spinflex pad. I have seen this problem a lot with limestone and especially travertine. I think it is just a natural erosion, like a “micro-spalling”   this is not from the pool water, but from rain water, it is not so smoggy here, so I don’t know if it would be acid-rain, but it could be. Any insight to this problem?  Any solutions?? They don’t want it to return.  
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