Rasendracudamani 14.48

14.48

viśudhyantyarkapatrāṇi nirguṇḍyā rasamajjanāt /
{copper:: śodhana}
tālapatrasamābhāni tāmrapatrāṇi kārayet //

the copper sheets are purified by immersion in the juice of nirguṇḍī.
One should make copper sheets resembling palm leaves;