Before you choose a piece

Four questions that usually come before the choosing. The answers, kept short.

• Gold karats explained: 24K, 21K, 18K and 14KWhat the karat number actually measures, how purity trades against hardness, and which karat suits which piece.
• How gold jewellery is pricedThe whole calculation, in the open: the day's rate, the making charge, the weight, and why two similar pieces cost different amounts.
• Finding your ring sizeTwo ways to measure at home, what the size numbers mean, and when to size up rather than down.
• Caring for gold and silverWhat actually damages a piece, how to clean gold and silver at home, and when to bring something in instead.