History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t9: (i) Gold Alloys
History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t9
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(i) Gold Alloys
v1.c13.s2.t9.1
Naturally occurring ‘electrum’ i.e. Au-Ag alloy was known to Harappan people but in latter period Au-Ag alloys (45-to 90% Au) were deliberately prepared to obtain a variety of colours and shades in the Gold ornaments and other domestic as well as decoration pieces. Today it is known that Au-Ag form a complete range of binary solid solution with lowering in the melting point of the alloy. Addition of Silver also increases the hardness and wear resistance of the alloy.
v1.c13.s2.t9.2
Similarly copper was added to the gold to impart hardness and better strength as well as more reddish colour to the metal. Au- Cu binary alloy system is characterised by the formation of Eutectic at 20% Cu, having a M.P. of 889°C. In recent years detailed studies of the binary, ternary and even quaternary alloy systems have been studied and published. The details of the binary alloy systems can be found in the book by Hansen(1958).
v1.c13.s2.t9.3
Since, in ancient times such information was not available, the development of critical alloy compositions must have been achieved by keen observation and long practice, and their secret must have been closely guarded.