Q: I have recently bought a knife which was quite expensive and advertised as stainless steel. Subsequently a friend told me that if it was good stainless a magnet would not stick to it. I tried it, and a magnet stuck to it quite strongly. Am I entitled to ask for my money back?

A: Stainless steel is not one single substance, but a whole family of steels with differing qualities, the only common factor being that they must have a chromium content of 10.5 per cent or higher. Other minerals can be present, the most common being nickel.

All this boils down to the fact that some are magnetic and some are not, and those which are magnetic include some cutlery steels. If you care to check around your home, you will almost certainly find that your stainless steel sink, and your table cutlery, are magnetic.

It is a common myth that “good” stainless is non-magnetic, so no, don’t ask for your money back.