Generally, with few exceptions, all jewellery needs to be polished at the end of the manufacturing process. Traditionally, this is done on polishing wheels impregnated with polishing compounds such as jewellers rouge. This is labour intensive and consistency of quality cannot be controlled. In mass production and in the more progressive workshops, increasing use is being made of mechanised polishing methods. These involve tumbling the jewellery mixed in with abrasive shapes or with polishing compounds and also by burnishing (hammering) the surface with hard materials such as steel pins and cones or porcelain balls. Generally, polishing is achieved in a series of polishing steps. Typical equipment includes tumblers (rotating barrels), vibratory barrels, centrifugal disc machines ('turbo'), centrifugal planetary barrels and magnetic burnishers. Electropolishing (electrostripping) is also practiced. Robots for polishing rings are now commercially available:

Use of robots for polishing gold rings
(courtesy United Robotic Integrations)

Other surface textures such as satin or matt finishes can be produced by various techniques such as sand blasting, vibratory pens and diamond machining. Chemical methods such as acid treatment or 'bombing' in a cyanide-hydrogen peroxide mixture are also practiced. This can enhance the colour to the deep yellow of pure gold by preferentially dissolving away the base metal and silver from the surface layer as well as giving a good finish.

Further information on finishing can be found in Gold Technology, No 26, 1999 and No 31, 2001.