A new process for jewellery production has been made possible through work undertaken by TWI and Middlesex University.
Sterling silver contains a small amount of other alloy additions, traditionally around 7.5% copper. One problem manufacturers face is that copper is oxidised below the surface of the metal when the alloy is heated during soldering. This gives the silver a bluish appearance, known as firestaining. To cover this firestain, the silver is often plated - in reality only a temporary answer which adds to manufacturing costs.
Peter Johns of Middlesex University says: 'We discovered that by replacing about 1% of the copper with germanium, firestaining does not occur. As an added benefit, the germanium slows tarnishing of the finished product'.
Conventional sterling silver is very difficult to resistance weld but this new material increases the resistivity and makes it easier to resistance spot weld.
The bracelet illustrated would normally be soldered. Instead the silver germanium alloy enables two small resistance welds to be made under each section. This makes the bracelet more flexible, opening up many new possibilities in jewellery design.
Kultakeskus OY, a silverware and jewellery company in Finland has recently obtained a licence to use this new technology and other world-wide licences are currently being negotiated.