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Posted: Tue Jul 02, 2019 8:20 pm
by Whippet73
So pleased to find this forum. We've just had some Marshall's granite slabs laid. Our contractor has used Bostik Cemetone Wide Jointing compound which has now stained the slabs and they look awful. We've tried a few things - is there anything that will get the marks off or are they like this forever now?
Is there anything that can be done apart from re-laying with new - removing the surface for example? I can lightly sand off the marks but imagine if we do that you'll just see sanded marks instead of the dark grey ones? Someone suggested using a diamond tip machine to remove the whole surface of the stone but that makes me very nervous as to end result.
Has anyone had this problem before and found a solution??
Marshall's/Bostik not much help.
Looking at about £2k of stone plus relaying which seems very drastic.
Pictures are here https://www.dropbox.com/sh....va?dl=0
Thanks so much 
Posted: Tue Jul 02, 2019 9:04 pm
by alrat
Whippet, I really feel for you, it does look bad and I bet it looked so good prior to jointing.
Did the contractor seal the slabs prior to using the jointing compound, on the surface and sides? How long is it since it was jointed? The compound really does look like it's stuck fast and penetrated the stone, which shouldn't have happened if they're sealed.
What did the contractor tell you, surely they're culpable, or did they just say it'll weather out in a few years as they drove off at high speed.
Posted: Wed Jul 03, 2019 7:27 am
by Whippet73
He's been trying to sort it to be fair but i think we are quickly running out of options.
No the stones were not sealed and it was about 10 days ago now..
Any suggestions? Or do they need replacing?
Thanks for your help.
Posted: Thu Jul 04, 2019 9:12 pm
by alrat
Sealing slabs before jointing is so important to help avoid this kind of mess, but surely the compound can't have been cleaned off the slab surface around the joints properly, for it to have penetrated and dried like this.
I hope others on here who may have experienced this can offer you a glimmer of hope, but to me it looks permanent. There are some specialist products specifically for this type of situation though eg. 'Floorseal Jointing Compound Residue Remover', never used one, but you may want to try.
Good luck.
Posted: Tue Jul 09, 2019 10:35 am
by Tony McC
I've answered this query via email - I really DO NOT like it when folk post questions here and email them to me, just to double up the amount of work I have to get through. 
Posted: Wed Jul 10, 2019 9:20 pm
by alrat
Whippet, assuming you found Tony's advice in his email useful, perhaps you'd consider posting it for the benefit of anyone else who may have this problem in the future.
Posted: Thu Jul 11, 2019 9:10 am
by Tony McC
Fair point, alrat - my annoyance with the OP shouldn't deprive others of what might be valuable advice.....
It's not really possible for me to comment on something I haven’t seen for myself, but it sounds like you have the 'picture framing' problem that can occur when using that particular jointing compound with that particular granite. The Bostik jollop is very, very resinous, and the Eclipse (G603 Granite) is very, very porous. Not a good mix.
I'm not sure whether it would be salvageable.
