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Deleted member 312768
Thank you for the advice I will check with the PB as well on it!Note that sanding only works with some stone and not all coping stone, so don't do it unless you're sure that it won't make it look worse.
Some stone can be damaged by sanding.
Sometimes, installers use grout wash water in a way that gets colored grout on the stone as a stain.
Washing the stone might help and maybe pressure washing might help but it can also damage some stone, so a few options, but be careful and try a test spot to see how any treatment will work.