In welding cast steel, the flux may consist of borax 1/4 lb., washing potash 1/4 lb., and a small quantity of powdered white glass. These should be melted together and pounded. Cast steel should be kept from the air when heating over breeze - not coal - and should not be raised to too high a temperature, as it is liable to burn. The blows should be light at first. The flux mentioned above should be thrown over the surface to be worked before the material is put into the fire, more being added afterwards as required.