Kautilya's Arthashastra 2.13.46

2.13.46

caturbhāgasuvarṇaṃ vā vālukāhiṅgulukasya rasena cūrṇena vā vāsayet /

For silver article either solid or hollow, silver may be mixed with half of the amount of gold; or by making use of the powder or solution of vermilion, gold equal to one-fourth the amount of silver of the ornament may be painted (vásayet) on it.