Now take a glass tube a quarter of an inch in diameter and 7 inches long, hold one end in a gas flame, and when red-hot draw it out to a fine point, then file round and break off the tip, leaving a small hole.
Now take a sound cork and squeeze it into the tube A as at C, drill a quarter inch hole through its center, insert the glass tube D, and the blow pipe is finished.
To use it you connect the pipe B with a gas bracket by means of a rubber tube, and attach the glass tube D to a pair of bellows by means of another piece of rubber tubing. The bellows should have an air-bag attached. Otherwise you will have a jerky, uncertain flame.
When you want to braze any article, bind the parts together with some very fine brass wire and cover with a little powdered borax and water; then lay the article on a piece of charcoal, and if it is necessary to preserve the temper of the steel you are about brazing, cut a potato in half and push each end of the steel rod into the halves, which will keep the temperature from getting too high.
Then turn on the gas and start your blow pipe, at the same time working the bellows with your foot, and by either pushing in the glass tube D, or drawing it slightly out, you can regulate the shape of the flame as required.
Fig. 2.
Fig. 11.
