The frame door on my marble shower broke, so I installed a new all-glass frame. It looks great. However, when the metal shower frame was bolted to the marble at the door sill, it was removed, leaving a big stain where the glass shower door is. Any ideas on how to clean this off? I was thinking of using CLR.
I tried everything to clean it up, to remove it, even a diamond pad.
The stain looks like scale left from water pooling at the bottom of the door then evaporating.
Scale is calcium carbonate, it can be dissolved with acids, for example: citric acid, acetic acid (cheap white vinegar).
However, marble is also calcium carbonate, which means you should be careful not to leave the acid too long. It won't dissolve your tiles, they're way too thick for that, but it will turn the surface matte instead of glossy. That shouldn't be a problem on the step, but it would be better not to spill some product on the rest of the shower.
You can use household anti-scale cleaning products which are usually concentrated acetic acid with a gel agent, being a gel it's much easier to keep it where you want to.
You could also re-polish the marble, but this needs a grinder, abrasive discs designed for this purpose and various abrasive pastes, removing the glass to get access, and it does take a while.
