Cloudy glass. White crust. Crystal again.

Usually just coated, and it comes off. Glass is hard and the film sits on top of it rather than in it. The exception is genuine etching, which can happen after many years in a very hard‑water area or after someone has used something abrasive on it – that doesn't come back, and it's one reason the tools matter as much as the chemistry.

Anything abrasive – green scouring pads, melamine sponges, scouring powder, wire wool. They appear to work because they take the film off, and what they're actually doing is putting fine scratches into the surface. Those scratches then hold moisture and minerals, so the next build‑up comes faster and is harder to shift. Dissolve it instead.

Check the manufacturer's information if you have it, or ask whoever installed it – many modern screens have a factory treatment that makes water bead off. On coated glass, acids and abrasives strip the treatment permanently, so use only a mild detergent and a soft cloth. If you can't find out, test a small hidden corner and watch for any change in how water behaves on it.

Never combine any acid – vinegar, citric acid, a descaler – with bleach or a product containing it, because that releases chlorine gas. Use one thing, rinse thoroughly, then another if you need to. Keep the door open, and wear gloves with the stronger solutions.

A squeegee after every shower, top to bottom, takes about twenty seconds and prevents most of it – the deposits form when water dries on the glass, so removing the water removes the problem. A weekly spray and wipe handles whatever slips through, and after that you're doing maintenance rather than rescue.