History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c20.s2.t4.6

v1.c20.s2.t4.6

A plant named *kuṣṭha* (*Costus speciosa*) grown in the Himalayas are often mentioned in ancient Indian medical texts. It is said that the leaves of this plant drop a fluid towards the earth having a colour like bright gold. This has a dyeing effect when comes into contact with the ashes of pure lead and quicksilver. It turns copper mixed with silver into a golden material (*Dhātuvāda* 12). *Hingula* alum, blue vitriol etc. are said to be favourable for importing colour to quick-silver (*Śiv. R.* VI. 15.50-51; *Rhr*, Pātala VIII). To brighten the blue tinge of the precious stone *nila* (sapphire), it is said that the gem should be placed in a bronze vessel filled with indigo juice mixed with the juice of citrus fruit (*Śiv. R.* VI. 17.112)