After several days of trying every concotion imaginable to remove the hardwater deposits from our glass block shower stall, we tried Bruce's GSR Glass Water Spot & Stain Remover, which I found at the local ACE hardware.
Also found their website:
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Used with 0000 steel wool, it removed the spots entirely, albeit with a couple passes of heavy scouring. But, it was a 5-year buildup.I suspect the mineral deposits may have actually been etched into the glass and that in fact I was polishing a layer away, rather than removing a deposit.
At any rate, the glass looks terrific.
Bill in Cave Creek, AZ.