According to Freedom55 "joinertake this :
I have soap buildup/calcium on Manhattan glass shower doors and ammonia
based cleaners take some of the stuff off but not completely. How can I
get these doors sparkling clean without scratching the glass?

Ammonia isn't very good at soap or calcium buildup. The "prepared"
"soap scum removers" work reasonably well. CLR (or equivalent, like
"ZEP" (Home Depot) calcium, lime and rust remover) work somewhat
better (at the expense of being a little more dangerous).

[CLR and ZEP are moderately strong acid solutions. CLR is
phosphoric/formic acid I think. ZEP is (mostly) a dilute HCl solution.]

In extreme cases, a carefully chosen muriatic acid (HCl) dilution
may be necessary - assuming you check to ensure it won't damage
anything, and provide _ample_ ventilation, breathing gear, skin
and eye protection!
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.