White film on limestone coping

[Peachtree21]

Greetings all,
Have a question that hopefully someone can shed some light on. Our pool was built and finished last June. We used limestone coping (salt water pool) and the coping only (deck is a sandstone) shows quite a bit of white haze. Any ideas? Thanks all.

 

[ajw22]

That may be mold or mildew on the stone.

Try spraying Wet & Forget on it and see if it clears up.

Wet & Forget Concentrate, No Scrub Outdoor Cleaner | Product Information

WET & FORGET CONCENTRATE | No Scrub Moss, Mold, Mildew & Algae Stain Remover. Easily remove stains from all your outdoor areas. Walkways. Pavers. Stone.

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[JoyfulNoise]

It’s efflorescence, not mold. Happens with all types of limestone and flagstone materials. Moisture is wicking up through the mortar bed from the pool walls (as well as splash out and rainfall) into the material. The water wicks up to the surface and leaves deposits behind that are white (calcium and other minerals). Happens to my flagstone coping all the time.

You have to seal porous stones to avoid moisture but sealants have their own set of issues. It all depends on how much effort you want to expend.

There are efflorescence cleaners for stone work but they are fairly expensive and if you don’t seal the stone after cleaning it then you’ll be right back to square.

 

[Peachtree21]

Thank you. I did have it sealed right after install of that makes any difference.

 

[JamesW]

I did have it sealed right after install of that makes any difference.

With what?

You might be able to buff it out, but you do not want anything too aggressive or you will damage the stone.

What is the ground water situation?

Damp soil will cause issues.

 

[JamesW]

Did you get a spec sheet on the stone showing the properties?

 

[ajw22]

Damp soil will cause issues.

Damp soil will also help mold and mildew.

Trying Wet & Forget is low cost and effort. You only know by trying.

 

[JoyfulNoise]

Thank you. I did have it sealed right after install of that makes any difference.

Good to know. The other possibility is that the sealer is breaking down and causing some of the chalkiness you see.

Sealers really only work if the entirety of the stone is sealed before it is installed and then a sealer (usually a high quality penetrating sealer) is applied every year or so. The gunite bond beam also needs waterproofing before anything is attached to it (tile, coping, etc). Unfortunately this is a fight against Mother Nature and laws of physics and chemistry … no one ever wins that fight.

You can try the Wet & Forget and see if it helps. No harm in doing that. But I have see this all before and I’d bet a box of donuts that it won’t work.

 

[ajw22]

You can try the Wet & Forget and see if it helps. No harm in doing that. But I have see this all before and I’d bet a box of donuts that it won’t work.

Wet & Forget does not have eggs in it and is probably less cost than the donuts.