Most types of Gemstones are vunerable to damage from the heat required to make a solder repair

Most gemstones are formed by crystallization from silicon with trace minerals in a supersaturated liquid . Because it is a natural process it is rarely 100% perfect and quite often there are trapped water bubbles within the gemstones particularly emeralds . These water bubbles which may only be visible when viewed with a 10 x lens can cause problems when carrying out jewellery repairs as most jewellery repairs require soldering which involves heating the piece  . This heat can cause the trapped water bubbles to expand within the stone   and crack the stone from the inside . some stones can be protected by the application of heat paste but most until recently required the stone to be unset so that the repair can be carried out on the metal and then the stone is reset again with all the risk that the setting claws may need to be replaced  A modern innovation has been the introduction of laser welding this equipment is very expensive £25,000 a machine and uses vast quantities of electricity but it produces intense localized pin point heat to weld repair   that allows the work to be carried out without risk to a set stone .   written by Clive Gilbert who studied gemology for three years at Sir John Cass college

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