Indian Sandstone White Stains

Postby gratian » Mon Sep 22, 2008 12:36 pm

I have recently had my patio laid with Indian sandstone. The stone looks great and the guy who laid it was professional and maticulous in his work so I guess this is not his fault, if indeed there is a fault at all.

A lot of the slabs now have white stains around the adges and one stone particular has gone almost completely white. The stones are surrounded by bricks and a lot of these have gone white too. The stains disappear when it rains or has water thrown on them but they re-appear when the slabs dry out. I read somewhere that it is salt and is quite normal for it to happen but I need to know if I need to do anything.

Any help would be greatly appreciated. I can send photos to anyone who would like to help me out (of the slabs that is!)
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Postby TheDoctor4 » Mon Sep 22, 2008 3:24 pm


This sounds like Efflorescence. If you have a look at the DIY Doctor project relating to this it may provide you with a little more information:

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Postby Annie71 » Sun Jul 03, 2016 1:18 pm

PLEASE HELP ...did you have any success with the salt marks on your indian stone flags?? We have recently had a large area laid and after 2 or 3 months it is now covered in this white salt and looks very unsightly. We have tried everything to get rid of it, so any ideas would be greatly appreciated.
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Postby Annie71 » Mon Jul 04, 2016 3:09 pm

Hi, so I'm assuming that once we have these Indian Stone flags covered in white salt, there is really no way to get rid of it and we have to live with it for what could be years until it eventually goes?
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Postby thedoctor » Mon Jul 04, 2016 6:06 pm


The powder you can see on teh surface is called Efflorescence as stated in the post below. You can find out more about it here. If you have a look at the DIY Doctor project relating to efflorescence, it may provide you with a little more information:

Essentially all stone/masonry etc is made up of minerals and salts from the earth. It also has both a moisture content. Some of the salts are water soluable and, while the water is in the stone (more after heavy rain etc) the salts dissolve. When it stops raining, the water in the material tries to escape to the surface where it evapourates. As it travels to the surface it brings the soluable salts with it. It evapourates on teh surface of the wall or patio and leaves the salts behind. This is what you can see.

On a very dry day, you can brush these salts off. Sometimes it takes a good brushing with a "SOFT" wire brush "CAREFULLY" to remove them. Then, to avoid the situation occurring again, it is a good idea to seal the surface of the stone/masonry etc.

The best stuff for sealing Indian Sandstone is (believe it or not) Indian Sandstone Sealer !! You can find out more about this by watching the video at this link where you can even buy the stuff.

Be aware that it is NEVER the case that a slab or brick or block etc will be entirely free of water. They absorb it from the air, the ground, spilt drinks etc. Treating with a sealer does not guarantee a salts free surface but it will reduce the efflorescence by at least 85% if applied properly.
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