Any acid, such as a vinegar (distilled vinegar is probably cheaper and leaves less of a smell to hang around), will do this: but with bathroom fittings like this, it may very well strip off the chrome coating (and brushing with a metal brush certainly will).
Plus from the look of the OP’s photograph, it may well be that the chrome is already a bit pitted and worn, in which case it might be simpler to just get new brackets.
Thanks!
Turned out this answer was the winner…
I went to buy rubber sheet to stuff below, but when I started work, I realised there were indeed a screw at the bottom to tighten to press up!
So I casually just tightened the screw and the glass is tight now.
Thanks everyone! I really learned so much… I have more DIY questions coming, so I really appreciate ur help.
Referring to this pic again,
What kind of rust is that? It’s unusual because it’s spotty and greenish, rather than usual reddish rust.
Regardless, is it possible to clean off the rust so the metal lols new again?
I suspect this is stainless steel - albeit old.