Making Tin Can Toys
by Edward Thatcher 1919
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HOW TO MAKE SOLDERING FLUID
Soldering fluid may be very simply made as follows: Pure zinc is dissolved in muriatic acid until the acid will not dissolve any more of the zinc. The solution thus obtained is then allowed to stand for a time and is then strained through a cloth and poured into a bottle which is kept tightly corked when not in use. First purchase about six ounces of muriatic acid, from a druggist. Take care not to spill any of this acid on the hands or clothes. Next get some pure sheet zinc. The sheet zinc employed for stove mats as it is sold in the plumbers' shops is not suitable for making soldering fluid, as this form of zinc is alloyed with other metals. Pure zinc may be very easily obtained from old dry batteries which may be found anywhere.
Remove the paper covering from the battery and crack it open with a hammer-remove the carbon from the center of the battery and dump out all the powdered material. Soak the zinc covering of the battery in warm water to remove any paper or material adhering to the zinc and then cut the zinc into pieces about 1/4 inch square. Find an old tea cup or earthen-ware marmalade jar and pour into it about half a teacupful of the muriatic acid. Set the vessel containing the acid out of doors or near an open window and away from all steel tools, so that the fumes of the acid may escape and not be breathed into the lungs or rust any tools.
Pour a small handful of the zinc cuttings into the acid. The acid will attack them at once and a strong bubbling action will result. When the bubbling action dies down add more zinc cuttings about every fifteen minutes. When the acid shows no sign of attacking the zinc as it is added, the acid is said to be "killed" and the soldering fluid is made. It may be used at once if necessary, but it will be much better if it is allowed to stand over night with the zinc residue left in it. It is then strained through a piece of muslin cloth into another cup or jar and the fluid is ready for use.
Soldering fluid may be kept in a wide-mouthed glass bottle or a marmalade jar; either vessel must be tightly corked when not in use. This soldering fluid may be used as a flux for any soft soldering operation in place of the soldering paste, but it is not as satisfactory a flux for the tin can work as the paste. The best use for it in connection with the tin can toys is to keep it to dip the point of the hot copper in occasionally to clean the tinning at the point of the copper. While the prepared soldering paste is best for all soldering operations connected with the tin work, other fluxes may be used if nothing better is at hand. These are resin, olive oil, cottonseed oil, automobile lubricating oil, and paraffin; but these fluxes are not very satisfactory in inexperienced hands. The soldering paste is best for all soldering operations.
Preparing a Joint for Soldering
Cleaning and Scraping
If the copper is thoroughly tinned and the heater and materials are ready for use as described in Chapter IV, then several practice pieces should be soldered together before attempting a joining on any real work you may have ready to solder. If the tin is bright and clean, it need not be scraped at the joint where the solder is to go. Rusty spots should be scraped bright if in the path of the solder. Paper, labels or paint must be cleaned away. If a can has been well rinsed with hot water when the contents are emptied, it will present no difficulties to the soldering, but a can that has been emptied but not rinsed presents a more difficult surface to solder; particularly tomato, fruit, or condensed milk cans. This, of course, applies only to the inside of these cans. Tobacco, coffee, cocoa, tea cans and the like offer no resistance to the solder without washing. The yellow lacquer used to line some cans need not be scraped off. Solder will adhere well to tin so treated, but paper, paint, etc., must be scraped from the path of the solder. The scraped part need only be a quarter of an inch in width on each side of the joint; the rest of the paper labels or paint will be removed in the hot lye bath used before painting the can.
The scraping may be done with an old knife, or a regular scraper furnished by the dealer in tinners' tools as illustrated in previous pages. When scraping the tin bright, do not scrape it so hard that all the tin will be scraped away from the inner sheet of iron, as solder will stick to tin much better than to iron. If the tin is not very dirty, a piece of emery cloth or sand paper may be used to clean the joint. Paint cans, cans that have contained stove blacking, rubber cement, varnish, shellac, etc., should be thoroughly boiled in a strong lye bath before soldering; paint is usually made of oxides and oxides are a sure preventive of soldering. The lye bath is made by adding two heaping tablespoonfuls of lye or washing soda to the gallon of boiling water. Cans boiled in this solution for five minutes will thoroughly cleaned and free from paint, paper labels, and practically anything likely to be found inside or outside of a can. The lye or washing soda, may be obtained at any grocery store. Care should be taken not to get any of the lye solution on the hands or the clothes as it is very caustic and will burn the hands and ruin the clothes if not immediately washed off. The work should be handled with a wire hook while in the bath and well rinsed with water when removed from it. The same lye bath is used before paint is applied to tin work, when all forming, soldering, riveting, etc., is done. It removes the flux, acid, and finger marks, leaving a clean surface on which to paint.