The art of lead burning has for many years been kept quite distinct from plumbing generally, it is nevertheless a branch of the trade, and one in which large numbers of plumbers are becoming very proficient. There is not required a large amount of skill or ingenuity in the execution of lead burning, because, as a matter of fact, when it is compared with first-class plumbing, it is not nearly so difficult to acquire. In most cases where lead burning was considered necessary, such for instance as lining large tanks in chemical factories especially for the manufacture of sulphuric acid, the lead was simply used in large sheets fixed with tacks to wooden framework and the edges burned together. Of late years, however, this method of burning the edges of lead together has been adopted for numerous other purposes, such as the lining of sinks for chemical laboratories, and lining cisterns in cases where the water attacks the solder.

The modern term for lead burning is "autogenous soldering." The word "autogenous" is rather an ugly one, and somewhat difficult to define, it pertains to the word "autogeneal," which means "self-begotten or generating itself" neither of which is very appropriate to the process of lead burning. In fact the latter term is not strictly applicable, because the lead is not burnt, it is only fused. The most suitable term would be "fusing process." Instead of saying "the seams are burned," it would be better to say "the seams are fused," as this would correctly describe the action that takes place.

The simplest kind of lead burning is that known as flat seams, and which as a rule is the only kind that plumbers are likely to make use of. Professional lead burners of course are required to burn seams in many different ways, even horizontal seams overhead are sometimes necessary. When the seams of sinks and cisterns have to be burned, the joints should always be arranged about 6 inches from the angles. Because if the seams are arranged in the angles the flame of the blow-pipe is likely to catch the surface of the lead at the side and burn them through before the seam is formed. It is best also to butt the edges of the lead and not to lap them. Then when each edge has been shaved about a quarter of an inch wide, take a strip of shaved lead about half an inch wide and direct the flame on the end until a drop is melted and falls on the seam, at the same time the flame should be directed towards the part of the seam to be burned, for the purpose of heating it. Then cause the flame to play upon the small drop of lead until that and the lead upon which it rests are fused, then draw up the flame quickly. This operation, owing to the intense heat of the airo-hydrogen flame, occupies much less time than it takes to describe it. So that the operator has to be quick in manipulating the blast if he wishes to avoid burning the lead over a much larger space than is desirable. It must not be supposed that a flowing seam like that produced by a copper-bit and fine solder can be formed by the burning process, this, under the circumstances, is not possible. Each wave has to be formed separately by a distinct application of the flame. The regularity of these waves will depend partly upon the skill of the operator, partly upon the quality of the blast and on the purity of the lead upon which it is being used. But like most other mechanical operations proficiency has to be attained by practice and ex-perience. When it is found necessary to burn seams on the vertical side of a cistern, the lap is generally arranged in a slanting direction for the purpose of forming a ledge for the drops of molten lead to rest upon until they are fused into the seam, which is formed of a series of drops, instead of waves. A similar appearance is obtained when seams are burned on an upright side of a cistern in a horizontal line.

Another very convenient way to produce a good flame for lead burning is to use compressed oxygen and coal gas. The oxygen can be obtained in steel bottles, this, being discharged under great pressure, is used for the blast instead of air, a bellows is therefore unnecessary.

When it is stated that a small sized blow-pipe of this kind with a supply of oxygen at the rate of 7 cubic feet per hour, and a gas supply through a quarter-inch pipe, will fuse a quarter-inch wrought-iron rod easily, the intense heat of the flame can be somewhat realized. Probably the oxygen method of burning would be rather costly where only small jobs of lead burning are occasionally required, but where there is a considerable amount to do the compressed oxygen would be far more preferable to the cumbersome and often troublesome hydrogen machine.

There is yet another method which has been adopted to a very large extent for lead burning, namely the use of a red-hot hatchet copper-bit.

The seam is placed, in the case of a pipe, on an iron mandrel, or if a flat seam, on an iron plate, and the hot copper-bit is drawn through, slowly fusing the lead together as it goes. A core or bed of sand will also answer the purpose.

It is, of course, a rough and ready way of doing the work, and it involves a large amount of time and labor in cleaning off the seams. But it is nevertheless effectual, and, where more skilful means are not at hand, it often serves the purpose in a rough way. It would not, however, do for general application, in fact, in numerous instances where lead burning is required, it would not be at all practicable.

In conclusion, it may be well to point out that the idea of substituting the burning system for soldering generally in plumbers' work is not at all likely to be an accomplished fact. It is all very well for special purposes, but the art of soldering in the modern style is too well established to be ever superseded by the comparatively inartistic methods of lead fusing. Not only is lead burning not so attractive or so sub-stantial in appearance as soldering, but it is not nearly so well adapted to general plumbers' work, and there does not at present seem any probability of it ever becoming a successful competitor.