of lead and tin will then be 2 and 1; 1 and 1; and 1 and 2. After the proper quantity of tin has been added, mix some powdered sal-ammoniac with the molten metals, and well stir the alloy; it is then ready for pouring into the moulds.
Making Coarse Solder from Composition Piping.
—Good composition piping is made of nearly all tin, or an alloy of tin and lead, in which the former metal is in excess, and formerly was much used by plumbers in the making of coarse solder, as the material consisted of odd pieces of small value. As, however, a great deal of composition tubing is made out of old metals of which lead, tin, antimony, arsenic, and zinc form the alloy, it is not advisable to introduce it into solder. Should it be done, the melting point of the solder would be raised, and in applying it to the lead to be joined together, would probably partly melt it. Neither do the metals named alloy in a thorough manner, but partake more of the nature of a mixture in which the constituents partly separate when making the joints, and some, especially zinc, show as small bright lumps on the surface. Joints wiped with what is usually called “poisoned metal” are difficult to make, almost invariably leak when on water service pipes, and are dirty grey, instead of bright and clean. The zinc could be removed from the mixture by the method already given.
Combined Solder and Flux.
—This consisted of equal parts of lead and tin made into fine tubing and afterwards filled with flux having resin as a base. “Tinol” is a paste made of finely powdered solder and a special flux, and there is also “Tinol wire” having a core of flux.
A “magic” solder, sold by hawkers, consists of the above tubular flux-filled solder of such low melting point that it can be fused in the flame of a lighted match.
Soft Solders that Melt in Boiling Water.
—The following soft solders melt at a temperature lower than that of boiling water: 1 part tin, 1 part lead, and 2 parts bismuth, melting point about 200° F.; 8 parts lead, 4 parts tin, 15 parts bismuth, and 3 parts cadmium, melting point 140° to 150° F.; 6 parts lead, 7 parts bismuth, and 1 part cadmium, melting point about 180° F. To ensure the alloys melting at the temperatures stated, the metals of which they are formed should be free from impurities, and care should be taken to prevent oxidation while making the alloys. When melting the metals, that having the highest melting point should be melted first, with a layer of resin over it, the other metals being added in the order of their melting points. The alloy should then be well stirred with a wooden stick, and poured quickly into moulds.
Re-melting and Overheating Solder.
—After solder has been re-melted a number of times or has been overheated, its content of tin will be reduced, and the solder will become poorer and coarser. The tin melts earlier than the lead and, being the lighter of the two, floats over it, and is thus fully exposed to the air, the oxidising effect of which on heated, molten metal is extremely active. The oxidised tin forms a dross, from which most of the tin may, however, be recovered by melting it with powdered charcoal, which combines with the oxygen and frees the tin. The addition of a little fresh tin is desirable.
CHAPTER III
Fluxes Used in Soft-soldering
Why a Flux is Required.
—The great essential to successful soldering is the chemical cleanliness of the surfaces to be united, and the proper use of a flux. Although work may be filed or scraped perfectly bright and clean, this is not the kind of cleanliness which is alone sufficient; there is always in course of formation a film of oxide present, and the duty of the flux is to dissolve this and keep any more from forming. Then, and not until then, will the molten solder “run” and spread over faces in the intimate contact necessary. If this vital precaution of cleaning and fluxing is always observed, the difficulties which many beginners experience in effective soldering will vanish.
Variety of Fluxes.
—There are a good many fluxes employed, including tallow (largely used for lead and pewter), resin (used for lead, compo-pipe, and tinned metals), hydrochloric acid, diluted (for zinc and galvanised iron), and chloride of zinc (the well-known “killed spirit”). The last-named is the most generally used, being suitable for tinplate, tinned iron, new zinc, copper, and brass. Sal-ammoniac is also utilised, sometimes in conjunction with chloride of zinc. The small worker who does but a moderate amount of soldering will find it convenient to use a soldering paste such as “Fluxite,” which is sold in a tin, and can be kept handy and applied to the work with a sliver of wood. “Tinol” is a paste flux in combination with a solder.
Preparing Zinc Chloride (“Killed Spirit”).
—Make this flux at home from finely snipped new sheet-zinc and pure hydrochloric or muriatic acid. (This is sufficiently cheap at any working druggist’s stores, and infinitely preferable to the contaminated oil-shop quality known as “spirits of salt.”) Stand the acid outdoors in a stoneware crock, add the zinc cuttings a few at a time at first, and when the first violent ebullition moderates, put in the rest. Be sure to provide an excess of metallic zinc, observing that a quantity remains undissolved after all chemical action ceases. Leave the metal in the liquor for twelve hours (covering the crock with a pane of glass), then decant and filter into a wide-mouth glass jar of handy size. Do not add water to the concentrated zinc chloride solution; dilution is sometimes recommended, but should never be done; the heavy, slightly syrupy, water-bright liquor should be used as it is. The alleged “cleaning” qualities of this chloride can scarcely be admitted to exist, and its principal function is to shield the surfaces of the work from oxidation; this it fulfils by the formation of a viscid glaze on the heated metal when the salt reaches its anhydrous (waterless) condition by evaporation. The addition of water to the flux, therefore, only uselessly prolongs the period occupied by evaporation, and wastes heat.
Always remove all trace of flux from finished work, first by soaking in water, and afterwards by washing with soda, soap, and water. Otherwise, there is the risk of the work being corroded.
Special “soldering solutions,” obtainable ready prepared, should not be used in preference to zinc chloride made as before explained or to the well-known paste fluxes.
Applying the Flux.
—A short heavy bottle about 3 in. or 4 in. high is best for