Venetian Borax: Refining Tincal with Lime

Native borax, tincal, came to Europe from the dried lake shores of Tibet and India coated in an earthy, soapy fat. Venice, then the Dutch, refined it in secret: the refined salt was called Venetian borax. One of their methods is recorded by Knapp, as Muspratt gives it in 1860: soften the tincal with water and a little slaked lime, wash it clean, dissolve it hot with a little chloride of calcium to take out the last of the soap, then crystallise it in lead-lined wooden cones. Borax is the flux of brazing and soldering.