For zinc-working, plumbing, gasfitting, and all kinds of work in sheet metal, a knowledge of the processes termed soldering and brazing is necessary. By these processes the edges of pieces of sheet metal are joined together, and although it is better for the amateur, for safety's sake, to have all zinc-working that he may require in the way of covering roofs, making zinc pipes, lining wooden cisterns, and similar operations, done by the professional zinc-worker, and to call in the plumber and gasfitter to rectify any leakage in lead pipes or gasfittings, it is as well that he should know how to make a joint in metal, whether sheet or pipe, and possess the few appliances necessary for doing so. If he can do no more than repair tin pots, kettles, etc., it will be of advantage to him, for the itinerant tinman seldom does his work effectually, and seems never to be at hand when his services are most required.

First, then, with regard to soldering and brazing. They may both be described as methods of uniting pieces of either the same or different kinds of metal with a strong and, if necessary, water-tight joint.

To effect this by the first-named operation, namely soldering, a compound metal called solder is used. This composition is melted, but the metals to be united do not require to be heated otherwise than through contact with the melted solder.

In the operation of brazing the metals to be joined must be raised to the melting point of the brazing composition, which is soft brass. Although this makes the strongest joint, the necessity for exposing the articles to such a great heat renders this operation inapplicable to many purposes.

Soldering is very useful for joining copper and copper, copper and brass, copper and iron, brass and brass, brass and iron, tin and tin, and tin and any other metal. If the joint has to stand a rather high degree of heat such, for instance, as the seams of a small copper steam boiler—a hard solder must be used. By hard solder is meant one that only fuses at a high temperature; a soft solder, on the contrary, fuses at a low degree of heat.

The following are the compositions of some of the most useful of solders and alloys, with the degree of heat required to melt each: