Stuart Noble wrote:

I think the truth is probably somewhere in the middle. Branded products
are often just over-priced basic chemicals but it's easier to find a
kettle descaler than phosphoric acid, and small amounts of anything are
always expensive.
Keeping some basic chemicals around the house is useful, whatever your
philosophy:
Strong alkali, caustic soda (although washing soda is adequate for most
jobs).
Strong acid, sulphamic (comes in crystals, safe to handle, but still ph1)
Solvents, white spirit, meths, isopropanol.
I exclude hydrochloric acid and ammonia, both of which blow your head
off with the fumes before you've actually used them for anything,

Rubbish.

Nothing beats ammonia for wood bending either..


and
don't do anything the above can't. I'm going to duck now before someone
tells me brick acid is a must-have, and I must admit that I've never
tried sulphamic on cement stained brickwork.

Brick acid is simply a cheap way to get a pretty strong acid.