Jewelry Making/Low-tech silver casting and moldmaking
Ian wrote at 2014-07-13 12:06:18
In our jewellery course we used borax to prepare the crucible and a pinch of borax stirred in with a carbon rod(or a dry stick) to help remove Impurities from the melted silver. If it helps I copied this about borax. The word tincal /ˈtɪŋkəl/ "tinkle", or tincar /ˈtɪŋkər/ "tinker", refers to crude borax, before it's purified, as mined from lake deposits in Tibet, Persia, and other parts of Asia. The word was adopted in the 17th century from Malay tingkal and from Urdu/Persian/Arabic تنکار tinkār/tankār; thus the two forms in English. These all appear to be related to the Sanskrit टांकण ṭānkaṇa.
It's a naturally occurring product that may not be known as "borax" to the locals. Naturally occurring Borax, (known by the trade name Rasorite – 46 in USA and many other countries) is refined by a process of recrystallization. Maybe something here will help. Good luck.