Melt the rosin and pitch together, add the other ingredients, and heat all in an iron vessel until all moisture is driven out, and the heated mass ignites from a burning chip of wood held over it; the flame is at once extinguished by a close-fitting lid.
In using the method for saw blades, they are first heated in a suitable furnace and then placed vertically, teeth upward, in troughs filled with the mixture. After sufficient cooling they are taken out and wiped with a piece of leather so that only a slight film of fat remains. They are then placed flat over a coal fire until the coating of fat ignites, which may burn as freely as required for great hardness. Screws, or other articles which require a less degree of hardness, are dipped into the hot mixture and brought to a white heat.
Composition to Toughen Steel.
| Resin2 | pounds. |
| Tallow2 | pounds. |
| Black pitch1 | pound. |
Melt together and dip the steel in the mixture when hot.
To Soften Iron or Steel.
Anoint the article all over with tallow, temper it in a gentle charcoal fire, and let it cool itself; or take a little clay, cover your iron with it, and temper in a charcoal fire.
Restoring Burnt Steel.
It is not generally known that burnt steel may be almost instantaneously restored by plunging it while hot in cold water and hammering it with light strokes on the anvil, turning it so as to hammer all over it, again dipping in the cold water, and repeating the hammering process as before. Try again if you do not succeed the first time.