In this section the employment of the less fusible of the soft-solders will be first noticed; the plumbers' sealed solder, 2 parts lead and 1 of tin, melts at about 440° F.; the usual or fine tin-solder, 2 parts tin and 1 of lead, melts at 340°; and the bismuth-solders at from 250° to 270°: the modes of applying the heat consequently differ very much, as will be shown.

The soft-solders are prepared in different forms suited to the nature of the various works. No. 5, p. 435, the plumbers'-solder, is cast in iron moulds into triangular ingots measuring from 1 to 6 superficial inches in the section. No. 8, the fine tin-solder, is cast in cakes about 4 by 6 inches, and 1/4 to 1/2 inch thick; and this and the more fusible kinds, are traled from the ladle upon an iron plate or flat stone, to make slight bars, ribbons, and even threads, that the magnitude of the solder may be always proportioned to the magnitude and circumstances of the work.

It is very essential that all soft-soldered joints should be particularly clean and free from metallic oxides; and except where oil is exclusively used as the flux, greasy matters should be avoided, as they prevent the ready attachment of the aqueous fluxes. It is therefore usual with all the metals, except clean tinned plate, and clean tin alloys, to scrape the edges immediately before the process, so far as the solder is desired to adhere.

Lead works are first smeared or soiled around the intended joints, with a mixture of size and lamp-black, culled soil, to pre-vent the adhesion of the melted solder; next the parts intended to receive the solder arc scraped quite clean with the shave-hook, (a triangular disk of steel riveted on a wire-stem,) and the clean metel is then rubbed over with tallow. Some joints are wiped, without the employment of the soldering iron; that is, the solder is heated rather beyond its melting point, and poured somewhat plentifully upon the joint to heat it; the solder is then smoothed with the cloth, or several folds of thick bed-tick well greased, with which the superfluous solder is finally removed.

Other lead joints are striped, or left in ridges, from the bulbous end of the plumber's crooked soldering-iron, which is heated nearly to redness, and not tinned; the iron and cloth arc jointly used at the commencement, for moulding the solder and heating the joint. In this case less solder is poured on, and a smaller quantity remains upon the work; and although the striped-joints are less neat in appearance, they are by many considered sounder from the solder having been left undisturbed in the act of cooling. The vertical joints, and those for pipes, whether finished with the cloth or iron, require the cloth to support the fluid solder when it is poured on the lead.

Slight works in lead, such as lattices, requiring more neatness then ordinary plumbing, are soldered with the copper-bit or copper-bolt represented in figs. 311 and 312; they are pieces of copper weighing from three or four ounces to as many pounds, riveted into iron-shanks, and fitted with wooden handles. All the works in tinned iron, sheet zinc, and many of those in copper end other thin metals, are soldered with this tool, frequently misnamed a soldering-iron, which in general suffices to convey all the heat required to melt the more fusible solders now employed.

Section IV Examples Of Soft Soldering 100151

If the copper-bit have not been previously tinned, it is heated in a small charcoal stove or otherwise to a dull red, and hastily-filed to a clean metallic surface; it is then rubbed immediately, first upon a lump of sal-ammoniac, and next upon a copper or tin plate, upon which a few drops of solder have been placed; this will completely coat the tool; it is then wiped clean with a piece of tow and is ready for use.

In soldering coarse works, when their edges are brought together, they are slightly strewed with powdered resin contained in the box fig. 310, or it is spread on the work with a small spoon; the copper-bit is held in the right hand, the cake of solder in the left, and a few drops of the latter are melted along the joint at short intervals. The iron is then used to heat the edges of the metal, both to fuse and to distribute the solder along the joint, so as entirely to fill up the interval between the two parts; only a short portion of the joint, rarely exceeding six or eight inches, is done at once. Sometimes the parts are held in contact with a broad chisel-formed tool, or a hatchet-stake, whilst the solder is melted and cooled, or a few distant parts, are first tacked together or united by a drop of solder, but mostly the hands alone suffice, without the tacking.

Two soldering tools are generally used, so that whilst the one is in the hand, the other may be reheating in the stove; the temperature of the bit is very important; if it be not hot enough to raise the edges of the metal to the melting heat of the solder, it must be returned to the fire; but unless by mismanagement it is made too hot and the coating is burned off, the process of tinning the bit need not be repeated, it is simply wiped on tow, on removal from the fire. If the tool be overheated, it will make the solder unnecessarily fluid, and entirely prevent the main purpose of the copper-hit, which is intended to act both as a heating tool, and as a brush, first to pick up a small quantity or drop from the cake of solder which is fixed upright in the tray, fig. 309, and then to distribute it along the edge of the joint.

The tool is sometimes passed only once slowly along the work, being guided in contact with the fold or edge of the metal. This supposes the operator to possess that dexterity of hand, which is abundantly exhibited in many of the best tin wares; in these the line of solder is very fine and regular. The soldering-tool is then thin and keen on the edge, and the flux instead of being resin is mostly the muriate of zinc, with which the joint is moistened by means of a small wire or a stick prior to the application of the heated tool; sometimes the workman cools the part just finished, by blowing upon it as the bit proceeds in its course; and the iron if overheated is cooled upon a moistened rag placed in the empty space of the tray containing the solder.

Copper works arc more commonly fluxed with powdered sal-ammoniac, and so is likewise sheet-iron, although some mix powdered resin and sal-ammoniac; others moisten the edges of the work with a saturated solution of sal-ammoniac, using a piece of cane; the end of which is split into filaments to make a stubby brush, and they subsequently apply resin; each method has its advocates, but so long as the metals arc well defended from oxidation any mode will suffice, and in general management the processes are the same.

Zinc is more difficult to solder than the other metals, and the joints are not generally so neatly executed; the zinc seems to remove the coating of tin from the copper soldering-tool; this probably arises from the superior affinity of copper for zinc than for tin. The flux sometimes used for zinc is sal-ammoniac, but the miniate of zinc, made by dissolving fragments of zinc in muriatic acid diluted with about an equal quantity of water, is much superior; and the muriate of zinc serves admirably likewise for all the other metals, without such strict necessity for clean surfaces as when the other fluxes are used.

The copper tool is only applicable to thin metals, because it requires such a degree of heat, as will allow it to raise the temperature of the work to be joined, to the melting point of the solder; and the excess of heat thus required for stout metals, is apt, either to burn off the coating of solder, or to cause it to be absorbed as a process of superficial alloying. It requires some tact to keep the heat of the tool within proper limits by means of the charcoal or cinder fire, but with the airo-hydrogen blowpipe, explained at page 454-6, it is easy to maintain any required temperature for an indefinite period.

Thicker pieces of metal, such as the parts of philosophical apparatus, gas-fittings, and others which cannot be conveniently managed with the copper-bit, are first prepared by filing or turning, and each piece is then separately tinned in one of the following ways. Small pieces, immediately after being cleaned with the file or other tool, and without being touched with the fingers, are dipped into a ladle containing melted solder, which is covered with a little powdered sal-ammoniac. The flux meets the work before it is subjected to the heat, and the tinning is then readily done; sometimes the work is in the first instance sprinkled with resin, or rubbed over with sal-ammoniac water; the latter is rather a dangerous practice, as the moisture is apt to drive the melted metal in the face of the operator.

Thin pieces of brass or of copper alloys, if submitted to this method, must be quickly dipped, or there is risk of their being attacked and partly dissolved by the solder. There is some little uncertainty as to iron, and especially as to steel, being well coated by dipping; sometimes a forcible jar or a hard rub will remove most of the tin, and it is therefore safer to rub these works with a piece of heated copper shaped like a file, immediately on their removal from the melted solder, which makes the adhesion more certain.

Larger pieces of metal, or those it is inconvenient to dip into the ladle, are first moistened with sal-ammoniac water, or dusted with the dry powder or resin, and heated on a clear fire either of charcoal, coke, or cinders, until the strip of solder held against them is melted and adheres; as the lowest heat should be always used. Another cleanly way of applying the heat, and which is also employed in tempering tools, varnishing, and cementing, is to make red-hot a few inches of the end of a flat iron bar about two feet long, to pinch it in the vice by the cold part, and to lay the work upon that spot which is at a suitable temperature; the work can be thus very conveniently managed, especially as it may be likewise placed in a good light.

Until the two parts of the work are thoroughly tinned, they must be well defended from the air by the flux to prevent oxidation; they are next made a trifle hotter than is required for tinning, and placed in contact whilst the solder is quite fluid, and a little additional solder is also used; when practicable the two surfaces are rubbed together to perfect the tinning and spread the alloy evenly through the joint; the work is then allowed to cool under pressure applied by the hammer handle, the blunt end of a tool, the tail-vice, or in any convenient manner. The stages of this practice, are similar to those of the carpenter, who having brushed the glue over the two pieces of wood, rubs them together and fixes them with the hand-screws until cold, as before adverted to.