Soften it up with repeated wipes with vinegar and shave it off with a razor blade. Once you're down to the glass, leave vinegar-soaked towels on the deposits to dissolve the calcium from the scratches and other glass imperfections.
it had well water in it.i got it aaway .i bought a glass safe razor blade but cut my self really bad where the point i think i needed stitches but i just used this nes skin stuff.but did that razor blader hurt with that vinegar on it and so did the new skin stuff