Dissolve scraps of cast steel in as small a quantity as possible of nitric acid, add finely pulverized borax and stir vigorously until a fluid paste is formed, then dilute by means of sal ammoniac and put in a bottle. When soldering is to be done, apply a thin layer of the solution to the two parts to be soldered, and when these have been carried to ordinary redness, and the mass is consequently plastic, beat lightly on the anvil with a flat hammer. This recipe is useful for cases when the steel is not to be soldered at an elevation of temperature to the bright red.

To Solder a Piece of Hardened Steel

To hard-solder a piece of hardened steel such as index (regulator), stop spring (in the part which is not elastic), click, etc., take a very flat charcoal if the piece is difficult to attach; hard-solder and as soon as the soldering has been done, plunge the piece into oil. All that remains to be done is to blue it again and to polish.

Soldering Powder for Steel

Melt in an earthen pot 3 parts of borax, 2 of colophony, 1 of potassium carbonate, as much powdered hard soap, to which must be added 3 parts of finely powdered glass and 2 parts of steel filings. The melted mass is run out upon a cold plate of sheet iron, and when it is completely chilled it is broken into small bits or finely powdered. To solder, it is necessary to sprinkle the powder on the surfaces to be joined several minutes before bringing them together.

Soldering Solution for Steel

A soldering solution for steel that will not rust

or blacken the work is made of 6 ounces alcohol, 2 ounces glycerine, and 1 ounce oxide of zinc.