Jewellery is held together with solder, that is, molten metal which is run between two pieces to join them together. There are two types of solder – hard and soft. Hard solder melts at a high temperature and soft solder, for example, lead, melts at a lower temperature. If hard solder is used on pieces of gold, because it has a similar melting point to the pieces being joined, it can penetrate the pieces resulting in a firm join. On the other hand, soft solder, which melts at a lower temperature than gold, can still join pieces together but results in a weaker join.

Lead soldering on a Victorian bracelet joint

Normally, the solder used for antique jewellery was the same carat or quality as the pieces being joined. Soldering takes some skill, particularly if a number of joins are needed. It may be necessary to use solders with different melting points so that earlier soldered joins were not melted by work on other joins.

Antique ring showing where lead solder was used to secure a loose claw

Given that we are dealing with antique jewellery that may be between 100 to 250 years, it is not surprising that it might need repairs. A common problem is a ring bezel separating from the ring band, for a brooch clasp to come loose or for parts of an item beginning to separate from its base. Jewellers needed to make repairs to items which might be affected by the use of the high temperatures required of a hard solder, such as items with enamelling, with seed pearls or organic gems. They also might have been looking for the easiest way to repair a small problem. To achieve this, they sometimes used soft solders, commonly, lead solder.

Solder marks on the back of an antique earring

Lead solder was apparently first used about 1850. It seems to have been associated with the invention of tin cans. It allowed for quick repairs of jewellery but its use had and still has some drawbacks. It can leave dark gray or silver marks and smears on a piece, albeit usually on the back of a piece, and can eat away at the underlying metal. It is very difficult to remove and replace and, because of the lead content, many jewellers do not want to try to remove it.

The presence of lead solder on antique jewellery should be disclosed by auction houses and retailers, particularly in online settings where you can’t inspect a piece physically.