General Remarks.
Soft solder, as referred to here, means solder that melts at a temperature of 300 degrees or less, and is so called because of the low heat required to fuse the solder. It is used almost exclusively on the quick melting metals and compositions, such as block tin pipes and Britannia metal. It is also used by pattern makers in soldering white metal, as it requires but very little heat to sweat it through heavy articles. It should not be used to join any pipes which convey hot water or other hot liquids, as it is readily acted upon and destroyed. (The composition of these solders is explained in a special chapter.)
The chapters on blow pipe work, also on bar work, will alone turn many dollars into the pockets of the plumbers who have courage and ambition to acquire this line of work. Many times small leaks occur in difficult places that can be readily repaired by the use of the blow pipe and a common candle.
The lining of bars with Britannia metal is coming more and more into general practice, and it usually requires a specialist in this line to do the work. The soldering of this metal with a blow pipe and an alcohol torch is an easy matter, and is described in a special chapter.
There is no reason why this work should not be done by a plumber, particularly in small cities and towns, and to aid such as have not had the opportunity to familiarize themselves with such work I append such diagrams as may seem useful and necessary.
CHAPTER II.
THE APPARATUS.
The apparatus used for lead burning is illustrated in Fig. 1. It consists of a gas generator, A; an air holder, B, and pump, C; mixing fork, e, and necessary cocks, f and g; combined scrubbing cup and fire trap, h; blow pipe and tips, i.
The generator consists of an acid chamber, j, and a gas chamber, k. These are connected with an acid supply pipe, l, which conducts the acid from the acid chamber to the gas chamber, and also serves as a balance pipe.
This feature makes the generator automatic in its action, for as soon as the gas in the gas chamber gets up sufficient pressure, the acid in the gas chamber k is driven slowly back through the acid supply pipe l and up into the acid chamber j, where it is held until gas is used. When the acid descends and submerges the zinc more gas is generated, replacing that which has been used. This form of generator will never blow acid like the floating generator.
The requirements of a hydrogen generator for lead burning are that it should be safe, economical and automatic in its action. It must be so constructed that it will generate gas enough to keep the supply constant, and deliver it at sufficient pressure to keep the flame steady. It must also be provided with a combination fire trap and scrubbing cup. This will prevent the explosion of the generator by firing the gas in the hose. This trap must be partly filled with a solution of blue vitriol to act as a precipitation cup. (This is treated under the head of “Scrubbing Cup.”)
The chief danger with an apparatus of this sort is its liability to accident by the careless use of the gas, and, as a mixture of hydrogen and air is very explosive, great care must be taken to exhaust all the air in the generator and tubes before attempting to light the gas at the blow pipe. The only way to make sure that the air is exhausted is to test the gas, as described under the head of “The Flame and Its Management.”