White marks on new(ish) black limestone patio

[AngryBunny]

Hello,

Last summer I had a black limestone patio laid. Pretty much straight away white marks showed up on it. I assumed I’d be able to clean them off but I was wrong…

I have read various posts on this forum which have been helpful however I’m a bit lost for what my next step should be.


I have to used LTP Grimex and it made little or no difference, even undiluted.


I’m wondering if I should risk using an acid based cleaner like ‘LTP Grout Stain Remover’. I’ve read never to use an acid based cleaner on limestone as it can lighten in. However I’ve also read this product can be used to remove the white marks.


So I’m thinking maybe I could do this. On a test stone try using some TP Grout Stain Remover. Then use LTP Stone Oil to seal. Finally using LTP colour intensifier and stainblock.

Does this sound sensible or can someone suggest an alternative approach ?

Thanks
Mark

 

[Old Mod]

@Lithofin BOB is the man to advise.

 

[Dumbo]

Is your stone sealed already

 

[AngryBunny]

Yes it is

 

[Tile Shop]

First off, don't use Grout Stain remover, Does just cause marks, it will dissolve the limestone and etch it. Instead, try the LTP Powerstripper to remove any previous sealer. Seal with the the Colour Intensifier. Not wise to mix oil based followed by synthetic as the latter will just film over. Just stick to the one.

What was it sealed with previously and also, is there a membrane under the concrete slab/screed?

Aaaannnnndddd....... if it is a newish screed, when was it laid (month), how thick is it, and long was it left to dry before tiling?

No further questions your honour.

 

[AngryBunny]

I had the patio laid for me so some of the questions I can't give an exact answer.

I've text the company to ask them what type of sealer was used.

There was a membrane laid. I know they used concrete to secure the stone to the ground. Was this incorrect? ( I know in a house you can lay a screed then leave it a month to dry out), is that what you're supposed to do with a patio as well and is this an issue with moisture escaping as it cures?

(It was laid in October I think)


(It's a bit disappointing as this company have good reviews, etc)

 

[AngryBunny]

I found a photo I took after they laid it (if that helps).

 

[Tile seller]

I think the same as Paul. C
Strip it and reseal. Can't see what else can be done.
I think for a similar look, slates a much better option for exterior use.
This blk limestone is prone to uv and acidic rain damage from what I've read.

 

[Tommcd]

Pavingexpert - The Curse of Black Limestone - http://www.pavingexpert.com/stonpv05.htm

This was the site I read before laying black limestone for my mum. It's awkward stuff. If it's sealed too soon salt crystals can be trapped on the surface, if it's not sealed and you get mortar on it you're buggered etc. This paving expert guy goes into great detail on his site about sealers, remedies etc.

 

[jimthetiler]

Natural stone will get a natural patina over time
the elements will do the job for you,Its a waste of
money and time trying to put a hold on nature.
stone looks better when it has aged.

 

[Simon Dale]

wear it in not out !

 

[Nicola]

'and you get mortar on it you're buggered etc'

Can you explain why??

 

[Qwerty]

LTP have a new 'black stone' product out. I will try and dig out the documentation to see what it says

 

[Qwerty]

LTP Blackstone - https://www.ltp-online.co.uk/prod/ltp-blackstone

More of a sealer restorer. Will still need a deep clean first.

 

[Phil -not a patio expert]

I had this problem, didn't read into the problem of black limestone before filling in the cracks with Mortar.

I have managed to removed 90% of the stains by a combination of Karcher and scrubbing with a little bit of 'pink stuff' cleaner. Then applied LTP external stone sealer (water based).

Hope that helps.