Borax reached medieval and early modern Europe as an imported commodity, gathered from natural evaporite deposits around certain high-altitude lakes in Tibet and central Asia and carried along long trade routes to European markets, where its distant and somewhat mysterious origin, along with its genuinely unusual chemical behavior, kept it comparatively expensive and prized. Its single most valuable practical property was as a flux: added to a soldering or smelting operation, borax dissolves metal oxides that would otherwise prevent solder or molten metal from bonding cleanly, allowing goldsmiths, silversmiths and other metalworkers to achieve strong, clean joins, a use that made borax indispensable in fine metalworking for centuries regardless of whether the metalworker had any interest in alchemy proper.
Alchemists studied borax as a genuinely unusual salt, distinct in origin and behavior from the vitriols, tartars and common mineral salts native to Europe, and some late medieval and early modern writers speculated about its possible role in transmutational work given its distinctive flux behavior with metals, though no reliable transmutation recipe built around borax survives. Its name, tincal, under which it was often traded and discussed, is itself borrowed from a Sanskrit or related term reflecting the substance's Asian origin, a linguistic trace of the long trade network that supplied it.