On Sun, 21 Apr 2019 11:15:26 +0100
Another John wrote:

Having a mug of tea with a mate the other day, I bemoaned the fact
that my beautiful mug (on the outside) had acquired brown stains (on
the inside) which can't be removed using the normal nylon scouring
sponge.

When it's mug cleaning time I just leave mine to soak overnight - that
usually soften the deposits enough that they will wipe off with an
abrasive sponge. Otherwise I'd choose limescale remover over bleach.

He said his Mum used to bleach their cups on a regular basis. I'd
heard of this before, but I've never gone near the idea, for fear of
poisoning myself.

Just a quick rinse will be fine, although It might still smell a bit
bleachy you'll come to no harm.