CHAPTER III 
Soldering (continued) Binding work for soldering—Soldering in plaster—Use of borax—Applica tion of solder — Soldering hearth—Jeweller's charcoal and wig— Management of flame—Various hints—Removal of borax—Composi tion of pickling solutions—Antidote for acid burns—Brazing. 

The separate pieces of metal which are to be hard soldered together should first be bound in position with binding wire. 
This wire can be obtained in various sizes. No. 20 on the standard wire gauge is a good thickness for general silver 
or copper work. No. 28 for finer work and jewellery. No. 32 for very fine jewellery. The wire is of iron, and on no account for gold, silver, copper or brass work should it be galvanised or tinned. For the metals with which such wires are coated, when heated, would alloy themselves with the gold or other metal of which the work is composed, and make a " burnt " line which would be very difficult to remove. So make sure that you use only plain iron wire. It generally has a dull, slightly rusted surface. Both the work and the iron wire expand when heated. But unless both are heated equally the work may expand a good deal before the wire has begun to stretch. As a result you may find that in soldering say, a square box of thin metal, the: wires have cut into the corners. It is not difficult to avoid such an injury to the work. You have but to make a 
Z-shaped kink in the wires every here and there as they pass round the box. These will allow the work to expand, yet they will not make the wires slack. In soldering the seam at the side of a tapering tube—part of a cone—some difficulty may be met with in keeping the wires which tie it together from sliding towards the smaller end, and so working loose. To prevent this take three lengths of wire and make kinks or knots at intervals. Then put these wires lengthwise of the tube, clipping their extremities round its open ends. Wires tied round the tube will not now slip down, for they cannot pass the kinks. 


Sometimes it is impossible to tie work together with binding wire. The shape of the parts may prevent it. For instance, a number of wires or other thin pieces radiate from the point at which they are to be soldered. Or grains and narrow cloisons are to be fixed upon a background. In the former case fix the wires accurately in position on a piece of wax. Plasticine or any other material which would tarnish the metal must not be used, for metal so tarnished is almost impossible to solder. Wax can be bought from any dealer in jewellers' materials. When fixing the wires in their positions tuck under each one of them a tiny V-shaped loop of binding wire, leaving the ends of the wire projecting above the wax. These little wire loops should be made from J inch lengths of thin binding wire. Put one of these little loops under each wire or boss as it is being stuck down in position on the wax. When all are arranged paint borax over all the joints which have to be soldered. Then mix a little plaster of Paris and pour it over the work. When set, the wax may be removed. The little loops of binding wire, with their ends firmly fixed in the plaster, will keep all the parts in place. Now clear away any plaster which may interfere with your soldering. Thoroughly dry the plaster. Add a little more borax wherever necessary and solder in the ordinary way. Grains or cloisons may be fastened down on to a background with gum. This should be mixed with borax. It is a good plan to keep a lump of gum on the borax slate, and rub a thick paste of it for use in sticking down these small pieces. Dry this thoroughly. Then go over the joints again with ordinary borax before soldering. But for further particulars of this work see Chapter VII, on Filigree. There are so many things to think about in wiring up any work for soldering that it is difficult to give general rules. Each case must be decided on its merits. 

All the metals used by the jeweller and silversmith, with the exception of pure gold, become oxidised when heated in air. A thin film of oxide forms on the surface. With copper this film is a dense black scale. All the alloys of copper, and they are many, show some trace of this oxide, with others. To solder work, however, it is necessary that the surfaces to be joined shall be clean and bright, even when red hot. To keep them clean they must be covered I with some substance which will exclude the air. A substance j which does this is known as a flux. Now for hard solders ; borax performs this duty splendidly. It is generally used in the lump form, not the powder. The lump of borax is rubbed with a little water on a small piece of slate. It grinds up into a white creamy paste which can be applied to the joint with a brush or feather. If several joints are to be soldered at the same heating put borax on them all. Then all of the joints will keep clean until you are ready to solder them. If you put borax only on the first you would have to cool the work down, and thoroughly clean the other joints before you could solder them, for a joint will not keep clean when the work is heated unless it is boraxed. Take care to work the borax well into the crack. Joints should be as close as possible, though the solder will fill a crack as thick as a sheet of writing paper. Should it be necessary, however, to solder up a wider gap it is well to plug it first with a scrap of metal. Borax, when heated, first boils up in a white scum, then it subsides and melts into a hard transparent substance, known as borax glass. In certain kinds of work, in which this boiling up of the borax might cause trouble, by moving parts out of their true position, the difficulty is got over in another way. Gum tragacanth is mixed with the borax on the slate, to keep the parts in place. Or, instead of lump borax, borax glass is used. It is ground with vaseline instead of water, 
and used in the ordinary way. It does not boil up at all. The solder will follow the borax, but it will not flow where there is no borax. If, however, there is some place upon which you particularly do not wish the solder to go, you may cover it with rouge, loam, whiting or tripoli, or a mixture of any of these, as an extra safeguard. 

With the borax the solder may be applied. It should first be cut into pieces of convenient size. This may be done by making a series of parallel cuts 1 inch long and |, TV or -jV of an inch apart, at the extremity of your piece of solder. It has already been rolled down to a convenient thickness. Then holding one finger against the sheet of solder, touching the ends of all the little strips, make another series of cuts at right angles to the first set. A number of tiny square or oblong pieces, or " paillons," of metal will be separated at each cut. They would fly all about if you had not your finger against them. Drop them on the borax slate or into a little box specially kept for them. Take very great care that no pieces of gold or silver, or any other material than just this solder, gets mixed with them. They might cause serious trouble. With the tweezers place a number of these little pieces at intervals along the joint or crack to be soldered. They should be sufficient in bulk to fill the crack. Not more, or you would have afterwards to file off the. superfluous amount. It would otherwise make the work look heavy. If, when the solder has been melted, you find that the crack is not sufficiently filled, it is quite easy to add a few more pieces of solder. To do this before the work has cooled down, with the tweezers dip each piece of solder into the creamy borax and place it in position, holding it down till the borax has boiled up. The solder will then keep firmly in position. If you omit to hold it down the borax may carry it, when it boils, right away from the joint. Another method of applying the solder, much favoured by silversmiths, is that in which the solder is first cut into long strips, perhaps | inch wide, and held in the left hand with pliers. When the work is sufficiently heated the point of the solder is touched on to the joint where required. Some of the solder melts instantly and flows into the crack. One advantage of this method is that the solder is not exposed for long to the heat of the flame. For the fusibility of solder is always impaired by long-continued heating, generally owing to the burning out of some of the zinc which it contains. Another advantage is that there are fewer marks left on the work where the solder rested before it melted. " Paillons " of solder generally leave a trace or " tail " to 
mark their temporary resting-place. But strip solder cannot be used for very small work, owing to the danger of disturbing the various parts, a difficulty which does not occur with larger work, which can be firmly tied together. Another form in which solder is used is that of powder, for soldering filigree work, described later. 

Large work should be placed on a hearth for the process of soldering. The hearth is an iron tray resting on a stand or bench about 3 feet high. The tray is fixed on a pivot, so that it can be rotated when necessary—a very great convenience, for in soldering it is often necessary to turn the work round. The tray is filled with coke or pumice stone broken to about 1 or 1| inch fragments. For the reason already given, take care that not even the smallest fragment of soft solder is allowed on this hearth. It is necessary in some cases to have a perfectly level surface upon which to rest the work during the process of soldering A most convenient slab for this purpose can be made in the following manner. Take a number of pieces of pumice stone and rub one face of each piece flat on a rough stone. Put all the pieces on a board with their flattened sides downwards. Arrange the pieces as closely together as possible, covering a space 9 inches square. Make a rim round about them from pieces of board 1 inch high. Then mix a bowl of plaster of Paris. To do this, fill the bowl one-third full of water. Sprinkle the plaster in by hand­fuls. Soon it will begin to show above the water in the middle of the bowl. Go on adding more plaster round the edges until the water will only absorb the plaster slowly. Let all the plaster sink in and then thoroughly stir the mixture for a good half-minute, taking care to get no more air-bubbles into the plaster than you can help. The plaster will now be of the consistency of cream, not quite thin like water feels. Take in your hand a little at a time of the liquid and throw it over the lumps of pumice stone. Try to fill the gaps between the lumps very thoroughly. You must be quick about this part of the work, as the plaster may be set in two or three minutes. When you have filled in all the gaps fill up all over, quite level. If you have been quick about the first part of the filling the plaster will still be liquid enough to use. You must not pour the plaster in at first, or the pieces of pumice would float out of their places. Level off the top with a straight piece of wood. Leave the work now and wash out the bowl before the plaster left in it has set hard. In five minutes the slab should be set, and feel warm to the touch. If quite hard knock off the wooden rim, and give the board upon which it rests a few blows with a mallet. The slab of plaster and pumice will then separate from it. Turn the slab over. Next fix it with plaster, mixed in the same way, into a shallow tray of sheet iron—not wood. You have now a slab with a smooth face of pumice stone, which will last for years. When thoroughly dried you can do upon it all the hard soldering that you wish. Its flat surface gives a very even support to work laid upon at for annealing or soldering. A sheet of asbestos, resting on any flat surface, may be used instead. 

When, however, a piece of work rests flat on a slab, and the flame from the blowpipe cannot reach its under side, the work takes a considerable time to get red hot. A few pieces of iron wire, or better, broken pieces of piercing saws, are laid between, to lift the work clear of the slab. Work, however, which does not require this even support is annealed or soldered on the loose pumice, coke or charcoal in the hearth.


Jewellery, as a rule, is soldered upon a flat piece of charcoal held in the hand,or uponajeweller's"wig "or"mop," Fig.34. This is a mass of  fine iron wire,bound together,with a more or less level surface. It also is held in the hand. Very small work is sometimes placed on a thin piece of sheet iron, perhaps 1 inch square, laid upon the charcoal. 

When using any of the hard solders you must bear in mind that the whole work must be made fairly hot before the parts near the joint to be soldered can be raised to red heat. For if a considerable part of the work is cold it will take away much of the heat, wherever you may have directed the flame; the exception being that with a long or thin piece of work one can sometimes bring the parts near the joint to the required temperature before much of the heat has had time to run away. But as a rule one works all over the article with the flame, watching carefully that no thin or exposed part gets too much heat, until the whole work is dull red. This you can tell easily if you move the flame right off the work every now and then. Any red-hot part will show at once. Then, with a few sharp blasts, the point of the flame being directed towards the joint, that part is raised to so high a temperature that the solder flows like water along and into it. Cease blowing or move the flame away immediately, or the temperature may rise so high as to melt part of the work also. Remember that a thin or small piece will get hot much quicker than a heavier piece. So if you are soldering large and small pieces together, watch carefully lest a small piece gets dangerously hot while the heavier parts are comparatively cool. To solder, say, a light setting on a large piece of work requires some judgment. For, to raise the work to a sufficiently high temperature may take minutes, yet a single sharp blast would be sufficient to melt the setting. The secret lies in keeping the heat away from the smaller piece and in playing on the large piece only. Thin projecting pieces or thin parts may be protected with a coating of loam, rouge, whiting or a mixture of any of these. 
 
Remember also that to make a sound joint both parts must be at about the same temperature. Otherwise the solder will flow and hold to only that which is the hotter. In soldering a long joint the tang end of a large file, held in the left hand, can be used to stroke the molten solder along. But as a rule the solder will flow towards the point which is hottest, if there is sufficient borax. Do not forget, in ;arranging thework on the hearth for soldering, that molten !solder is a liquid, and therefore runs downwards more freely than upwards. Copper may be raised to nearly a white heat before it will melt: brass, however, goes much sooner—atayellowheat. Silverlookspinkwhen''red-hot and the flame has been moved away. It will melt before it gives a white glow. Gold changes colour very little before reaching its melting point, but then it collapses very sud denly. So use considerable care, and manage your flame so that no thin part gets a sharp blast. Remember to move the flame right off the work for a fraction of a second every now and then. You will thus be able to see easily when any part is getting red hot. 

To ensure a good joint, the one great rule is—cleanliness. All the surfaces should be chemically clean before the flux is applied. In some cases, when for example a sheet of gold is to be backed with silver, and the failure of the soldering at any place might have serious consequences later on, the work is treated as follows. The surfaces are cleaned by boiling them in diluted acid, afterwards in a solution of washing soda and water, and again in clean water. The surfaces should not afterwards be touched by the hand, for that might leave a trace of grease, but they should be immediately painted carefully with the borax solution and tied together with stout iron wire. The solder is laid along one long edge and one side. The work is now heated,andthe soldermaybedrawn rightthroughthejoint. When the borax has been removed, the combined sheet is rolled as thin as may be required. If the joint is sound no blisters will be formed between the two parts of the plate. 
 
In soldering a wire on to another part of the work you may have some difficulty in keeping the solder from running on to and thickening the wire. This is a particularly disagreeable habit, for it quite ruins the appearance of a twisted or plaited wire if it is clogged up in this way. To avoid this difficulty you must take care that the heat reaches the wire only through the work—not directly from the blowpipe itself. The heat may be applied underneath, for example, so that the flame does not touch the wire at all. The work will then be the hotter of the two, so the solder will not rush to the wire. Another method is that of running solder over the surface of the work where the wire is to come, and afterwards putting the wire in place, 
•boraxing and reheating till the solder flows and grips the wire. 

To solder the two. halves of a ball, or bead, together. Inside, round the rim of each half put borax and solder. Heat each half separately so that the solder flows right round the edge of each half ball. Now rub or file the rims quite level, borax each half, tie the two together, and heat until the solder runs through the joint. You may be quite certain that by following this method you will always get a sound joint. Do not forget that you must always leave a hole for the escape of the air when soldering up any bead or other hollow article. If you omit to leave one, the pressure of the heated air inside when soldering may burst the work. Cases have occurred where jewellers have lost their eyesight through neglect of this simpleprecaution. 

To unsolder a piece of work. First think how you can manage to separate the parts when the solder is melted. You may be able to lift or knock off the loose piece with the tongs; or you may so arrange it that the parts will spring or fall open. You may find that instead of lifting the piece off, you would lift the whole work instead. In such a case tie the work down and perhaps fix another wire to the loose piece, by which you may pull it off. Paint the joint well with borax and apply loam, rouge or whiting to any parts or joints which are not to be disturbed. Then heat the work till the solder runs, and immediately remove the loose piece. 

To remove the borax after soldering various " pickles " are used. For gold a solution of nitric acid and water is made to boil in a porcelain bowl, and the work left in it until all the melted borax has disappeared. Eight parts of water to one of acid is a good proportion to use. The boiling solution dissolves also any alloy (copper or silver) which may be present on the surface of the gold. It will also remove lead, should any of this material be present. So the work when it leaves the acid has an exterior of pure gold—the alloy having been removed, but to an infinitely small depth. For silver or copper a solution of sulphuric acid (vitriol) is used. Say 6 to 10 parts water to 1 of acid. The colour of silver after pickling is pure white. 

In mixing these solutions remember that if you pour water into acid you will probably have an explosion and receive some damage. While if you pour acid into a much greater bulk of water nothing will happen except that the water will get warm from chemical action. The sulphuric acid solution is generally put into a copper bowl or pan with the work, and heated till it boils, when the borax will have been dissolved. Avoid any splashes, hot or cold, from these solutions. They burn holes in clothes, and may make serious burns on flesh. If you receive a splash, wash the part immediately with plenty of water. And, if necessary, apply a mixture of whiting and olive oil to the part. Com mon washing soda rubbed on the place after washing will do instead. It is usual to keep pickle in a large pan of glazed earthenware, or of lead. The solution acts more slowly when cold, but if work is left in it for an hour or two the borax will be dissolved. Large work, for which you may not have a big enough copper pan, can be cleaned in this way. But you can hasten the process by repeatedly-heating the work and plunging it while red hot into the solution. The oxides formed on the surface of copper by heat are also removed by the acid solution.

Work which has been in pickle should always be washed thoroughly in plenty of water immediately it is removed from the solution. If there are any hollow parts to the work it is usual to boil it in soda and water to remove any trace of the acid. If you do not take this precaution, some of the acid which has got inside will run out or dry out in crystals later on and cause trouble. Binding wire should always be removed from the work before it is pickled. 

It is well to remember that solder will not melt, until the heat is raised to a dangerously high temperature, unless borax is in contact with it. So, when a work has to undergo several successive solderings—and it may have to " go through the fire " twenty times or more—it is usual to boil it out after each soldering, to remove the borax from the joints already made. As a further protection a coating of loam, whiting or rouge may be painted over any joint which you wish to remain undisturbed. 

To join pieces of copper, brass, iron or steel together by brazing, first fit the pieces together closely, and bind them with iron wire. This should not be thinner than that of which an ordinary (brass) pin is made. It may be a good deal thicker if the work is heavy. Apply borax in the ordinary way (p. 17) or in the form of powder. Then put some brass spelter or wire on the joint. Brass wire makes a good solder for iron or steel, but it would be dangerous to chance it on brass, unless you knew pretty accurately the composition of both brasses. Make sure that the wire or spelter will not move away or fall off when the borax boils up. The wire may be bent round the joint or bound in place with iron wire. Build the coke round about the work and heat until bright red, nearly white hot. The spelter or wire should melt, follow the borax and run into the joint. Should it not run easily add a little more borax. When cool the borax may be removed by pickling or scraping, and the joint filed smooth. It will show up as a faint yellow line against the grey iron.