The Brew Cabin

High while I was out my B in law grouted my nice new flags, he used a dry mortar mix. Problem is I had washes them down and some of the joints were still quiet wet including edges. So we now have what appears to be a dark wet mortar looking stain. Obvious question what to do to get it off, it was only last night so still not completely dried out. I tried a stiff scrubbing brush but that only appears to take some off. Suggestions off friends let it dry then scrap it its sandstone so will be ok. Second suggestion wait until dry use edge of a chisel or coarse sandpaper, the third and I have explained that’s a none starter was brick acid. When I explained about brick acid he said it will be ok just use a bit on a small brush. So over to the experts PLEASE HELP me!.

If it was only done last night i would use a powerfull jetwash, not the domestic type but hire a good one in, it may cost 25 bills but its easier than waiting for the stains to wear off and putting up with the wifes aggro. Note this may remove some of the pointing as you are obviously going to be spraying across the joints but the harder the joints the more stubborn the stains.

I'd suggest a wire brush - it does less damage to the stone but does get rid of the still fairly-green mortar.