Fig. 47.—Position of Candle and Blow Pipe.
To operate: The candle should be lighted, and when it burns well and freely the tip of the blow pipe should be brought close to the flame and slightly above the wick, a, Fig. 45. Then blow lightly through the blow pipe, and a pointed clear blue flame from 1 to 2 inches long, which will burn paper or char wood at a distance of 6 or 8 inches from the flame, will be the result. The flame is hottest and best when it shows a perfect cone-shaped blaze, and is obtained by a very moderate blast. The variation of the blaze can be noted by commencing to blow very lightly and increasing the pressure gradually. The flame will then show all stages from a smoky flame to a long blaze that cannot be concentrated on any small surface. The little sharp tip is where the hydrogen burns, and is the hottest part of the flame, being the part that is used for soldering.
Now, having noted these peculiarities, and knowing the perfect flame by sight, we will proceed to acquire the steady blast. The blow pipe should be held between the lips, which will form a tight packing around it, and must not come in contact with the teeth. The cheeks are then inflated, which will have a tendency to throw the tongue back to the throat and prevent the air in the mouth from blowing out through the nose. Now, by contracting the cheeks, and throwing the tongue slowly forward, the air will be forced through the blow pipe. This action is assisted when exhaling air by the pressure of the lungs, but when inhaling air the muscular contraction of the cheeks is depended upon entirely for the blast.
The ability to keep up a steady blast is merely a trick, or knack, and is learned with a few hours' practice; when learned, the length of time that the blast can be kept up depends solely upon the strength of the muscles of the cheeks of the operator. If these did not tire, the blast could be kept up for an indefinite time. Having learned to keep up the steady blast and get a perfect flame, the beginner will want to practice soldering. The blow pipe method of soldering has for its range of work everything that can be soldered, from Britannia metal to platinum, but the only metals that are used by the plumbers are tin and lead and their several compositions, so we will confine ourselves to the study of those metals.
Kinds of Solder Used.
In soldering any metal the solder should be so proportioned that it will melt many degrees lower in temperature than the metal to be soldered. Otherwise it would be quite probable that holes would be burned in the work before the solder would melt. There are exceptions to this rule, however; for example, lead burning, where one piece of lead is fused to another. As also with Britannia metal, it can be, and is, soldered with its own material, but it would be likely to have holes burned in it occasionally, and to avoid this a solder mixed for that purpose should be prepared. Two receipts are given here for quick melting solders that are suitable for this work. The first is preferred, but the second will answer the purpose.
Solder No. 1: Procure 4 ounces of pure lead, 4 ounces of pure tin, and 2 ounces of bismuth. The lead should be melted first and thoroughly stirred and cleaned. It should then be allowed to cool to the melting temperature of the tin, which should then be added. Lastly add the bismuth. The whole should then be stirred and poured into a suitable mold into very thin strips, about the size of a No. 8 wire, making strips of solder that can be rolled up and carried in the pocket.
Solder No. 2: This solder is composed of two parts of tin and one part of lead. These should be mixed as described above. To have success in making solders several points must be observed. The metal melting at the highest temperature should be melted first, which must then be allowed to drop to the melting temperature of the next metal to be added, and when ready to pour into molds the mixture must be stirred, as the specific gravity of the several metals differs considerably, and unless constant stirring is resorted to the mixture will partially separate upon cooling, and the result is an irregular solder that will not do the work.