Rasendracudamani 14.37

14.37

triṃśadvāreṇa tattāraṃ bhasma saṃjāyatetarām /
{effect of māraṇa of a bhasman}
rāgaḥ syāt sarvalohānāṃ puṭādhikye na saṃśayaḥ /
rañjayanti ca raktāni dehalohobhayārthakṛt //

for thirty times, that silver becomes completely reduced to ash.
Colouration certainly arises in all metals from an excess of calcinations, without doubt;
and when reddened, they colour [other substances], achieving both the transmutation of the body and of metals.