Borax is often used as a flux for forge welding. Borax is also used mixed with water as a flux when soldering jewelry metals such as gold or silver. It allows the molten solder to flow evenly over the joint in question. Borax is also a good flux for "pre-tinning" tungsten with zinc – making the tungsten soft-solderable. A mixture of borax and ammonium chloride is used as a flux when welding iron and steel. It lowers the melting point of the unwanted iron oxide, allowing it to run off. Pack size of 500g

Chemical composition: Na2B4O7 - 10H2O