Before you start, yes, I did know that grout would be hard to remove from the slate. So did the guy doing the job, as I made sure that we discussed it before hand. I was of the impression that he was going to grout carefully, more like pointing. We went away for the weekend while he finished the job, and he did no such thing.
One corner of the room looks ok, so I guess that'd be the corner that he started in, and then he got impatient and rushed the rest of it, and left us with this mess.
He did put a coat of sealant on before grouting, but given how hard it appears to be to remove, I'd say that's not helped very much.
What's the best course of action? I have some grout stain remover, which says it's 10% hydrochloric acid. If I use it neat and scrub like hell (with a standard washing up scourer sponge) I can make an improvement. A very slow, tedious, improvement.
I'm guessing this is the best I can hope for, but maybe I could be using a stronger acid? What's the best scrubbing implement? Could I be using some drill-attached agitator of some sort?
Any tips hugely appreciated, thank you!
- The stone: https://www.stonetilecompany.co.uk/natural-charcoal-grey-slate-tiles-modular-set
- The grout: https://www.stonetilecompany.co.uk/flexjoint-grout-grey-10kg
- The sealant: https://www.stonetilecompany.co.uk/5-litre-mattstone-natural-stone-impregnating-sealer
- The stain remover: https://www.stonetilecompany.co.uk/1-litre-grout-stain-remover-tile-cleaner