How do I get old calcium off a shower door?

Have you tried glass stove top cleaner? That stuff works AMAZING on my shower door when it gets stubborn marks like that!

Beth, I believe in working smarter, not harder. If I had to remove calcium deposits from a glass shower door, I'd use (& I have done this many times &it works beautifully) CLR liquid cleaner, it's made for precisely that problem. Yes, it will cost you a little$$, but it will get the job done quickly and so well that you will be very happy you bought the CLR product. CLR= calcium, lime, & rust cleaner. If U have CLR deposits it means U have "hard"water. Try the CLR Product, you'll be glad U did. In fact if that's a constant problem for U, U could either invest in a whole house water softener being installed in your home, or invest in a few bottles of CLR (calcium, lime & rust cleaner) at a time. It's good for more than just the shower door. 😉

I agree CLR is great.

put straight CLR on paper towels and put them on the door( they can't be so wet they fall off) let them sit awhile to dissolve spots then take them off and scrub with fine steel wool or green scrubber sponge you can use the single edge razor blade with the CLR too spray on scrape off rinse well wth hottest water you can get. use gloves

Nothing better for the built on stains, like in an old toilet. Be sure to wear protective gloves and goggles for safest work. Good luck!