Waterproof jewelry does not need maintenance to stay safe. It needs a little to stay looking new — because the steel and the finish on top of it age at completely different rates.

Acetate is why a big earring can weigh almost nothing and hold its colour all the way through. It is also why it does not belong in a pool. Here is what water and heat actually do to it.

Watches have a rating system. Jewelry does not — which means "waterproof" on a jewelry page is whatever the brand decided it means. Here is how to work out what you are actually being told.

Three kinds of water, three different attacks. Chlorine, salt and sweat each damage jewelry in their own way — and the metal that shrugs off one is not always the metal that shrugs off another.

Solid gold, gold-filled, vermeil and gold-plated are four different things with four different lifespans, and in the US they are legally defined terms. Here is what each one means and what it buys you.

"Surgical steel" has no fixed definition — several very different grades are sold under it, including some chosen for hardness rather than for sitting in a piercing. Here is what the grades mean and which number to look for.

If earrings make your lobes red and itchy a day later, it is almost certainly nickel. Here is how to tell it apart from ordinary piercing irritation, and how to decode the eight phrases a product page might use for metal.

Green skin is copper — not nickel, and not an allergy. Here is which metals do it, why plating only delays it, and why "what is it plated over" is a better question than "is it gold."

A flat back stud is an earring with a smooth disc behind the lobe instead of a butterfly clutch. Here is the anatomy, the actual measurements, and why the back is what makes it an earring you can leave in.