Watching somebody wipe joints, a clear description of how it is done, a thorough knowledge of the theoretical process, and acquaintance with the traits and qualities of the materials used, are essential; but practice in the art of wiping joints has more to do with making one proficient than has mere practice to do with proficiency in any other line of work. A Hottentot would succeed about as well in engrossing a set of resolutions, upon his first introduction to English and a pen and ink, as the most skilful person in other lines would in the work of wiping a joint at the first attempt. One may give the closest attention to the manual operations of making a thousand joints when the cloth and ladle are in the hands of someone else, and yet fail to remember the how and wherefore of a hundred movements absolutely necessary to success. Some general remarks are therefore all that will be of real benefit to any one previous to practice.

The same general result must be attained under a great variety of conditions, regardless of position or size or character of the pipe. The temperature and composition of the solder; the temperature of the weather; the kind, size, and position of the joint, etc., must be reckoned with in every instance, and each modifies the proceeding more or less at some stage.

Before commencing to wipe a joint, one should be positive that it is firmly set; that the cleaning is well done and of proper length; that the junction of the ends is well made, so that solder will not run through into the pipe; that the surrounding edges are well soiled, pasted, or otherwise protected, so that the solder will not adhere except at the cleaning; that the pipe is dry inside and outside; that no undue current of air is passing through it; that there is enough solder in the pot to get up the heat and do the work; that the solder is hot enough; and that the cloth is in good condition.

To prepare for a joint, square the end of the pipe; see that the bore is true; rasp the spigot end evenly down to the bore, a little more obtuse to the outside surface than it is intended to make the boring or opening of the receiving end to that of the interior surface. Always rasp against the end of the pipe, so that no burr is made on the inside and so that none of the raspings get into the pipe. If the receiving end is to be opened with a turn-pin, the rasping on the spigot end should be made according to the taper of the turn pin, and the bell end should be rasped down only partially, leaving stock enough to stretch when the end is expanded with the turn-pin. If the receiving end is to be opened with a tap-borer, then the spigot end must be rasped down in accordance with the angle of its boring. A coarse rasp will do to rough the work with; but one of fine teeth should be used to do the finishing so that the shave-hook will remove its marks. When the ends are thus prepared, soil them back three or four inches; and when dry, clean with a shave-hook, cutting rather deeply at the beginning of the cleaning so that there will be a slight thickness of solder at the edges of the joint; otherwise it would be impossible to wipe the edges clean and perfect, because the feather edge will chill too quickly. Before setting the joint, the tip edge of the spigot end and the bottom of the receiving end should be soiled, so that the two soiled parts will come together when the pipe is in place. This keeps solder from sweating through into the pipe.

The length of cleanings does not increase with the diameter of the pipe. The idea is to have the solder contact surface in proportion to the strength or purpose of the pipe. A round joint on 5/8-inch pipe and one on 8-inch soil pipe should be about the same length - 2 to 2 1/4 inches. On 4-inch soil pipe, the average width of a joint is about 1 1/2 inches. When the pipes to be joined are of different metals, it is best to increase the length of the joint somewhat, or extend the tinning. For instance, on copper pipe - especially for distillery use - some kind of galvanic or corrosive action takes place which destroys the union between the solder and the metal of the pipe. It is therefore usual, on distillery work, to tin across the end of the pipe and back on the interior, in addition to the regular joint s rface outside, making the tinning continuous, as its length and continuity seem to determine the period of time the joint will last.

Difference in the ratios of expansion, causing a shearing action, appears to have much to do with the life of joints when lead and brass, lead and copper, or lead and iron are joined together by wiping. This is noticed more on water-back connections than elsewhere in the regular line of plumbing. When lead is joined to lead, the difference in the coefficients of expansion for the mass of solder and the metal of the pipe with which it is in contact, is so slight that little trouble is experienced in this way. The contour of the joint may be decided by allowing the thickness of solder at the middle to equal one. and a-half times the thickness of the wall of the pipe. This holds good for supply pipe where the solder used is 40 to 45 per cent good tin and 55 to 60 per cent pure lead. On thin wall soil and waste pipe, or where coarser solder is used, twice the thickness of the wall is better The solder forming the joint must be patted up compactly before wiping.

The beginner should keep the solder hot, leaving the pot in the furnace while practicing, so that he can put back and re-melt the cold batches from time to time, and continue to pour and re-wipe without loss of time. He can do no better than to try to imitate the motions of those who know how, whether he yet fully comprehends the reasons or not. Practice will soon teach him a few points which words cannot explain to the inexperienced. Lead and tin, not being of the same specific gravity, stratify more or less when melted, the tin rising to the top. For this reason, the molten mass should be skimmed and well stirred before dipping out any to wipe with. Never stir solder until ready to use it. Let the novice take the cloth in the left hand, holding it forward so as to cover the tips of the fingers, and take a ladle of solder in the right. Hold the cloth under the cleaning and drop the solder drop by drop upon the cleaning at different points, gauging the number, rapidity, and size of drops according to the heat of the solder. A single drop of solder too hot, may melt a hole through a thin wall pipe after it is pretty well warmed up. Keep the ladle moving so that the drops will fall in different places. When some solder gathers on the cloth, put it up on top again, and drop solder on it. When more runs down on the cloth, hold it against the bottom of the pipe to warm the bottom; and continue to drop solder from the ladle, more particularly now about the edges and even extending the pouring two inches or so out on the soiled part of the pipe on each edge, which will help to warm the pipe and provide heat in the pipe adjoining the edges of the joint to help keep the joint hot enough to wipe the edges clean before they chill.