Technology and Control of Red-Colouration of Brazilian Agate

The jadewares made from Brazilian agate, which is always unwell-looking white or light gray, even dark gray, can be coloured into nice-looking red by soaking it in colouring agent and heating it in a proper temperature. The colouring mechanism, process and influencing factors are discussed in detail. It indicates that the colouration of agate, which is complex and comprehensive, can be affected by various factors such as raw agate structure, jadeware surface condition, composition and acidity of colouring solution, soaking temperature and time, heating temperature and time, and so on. The optimums for high quality products are proposed.