Working with Metals
( Originally Published 1937 )
TIN (which is really sheet steel with a thin plating of tin) is the traditional New England material. Itinerant tinsmiths used to travel through the country, peddling needles, thread and buttons as well as doing tinkering and repairing. They made sconces, candlesticks, pie and cake tins, spice cans, etc. Many of these old products of the tin-smith's art are still in the attics of old homesteads. They serve as interesting models for the metal worker to study as starting points for his own designing. A great deal may be learned about the craft by measuring one of these pieces and attempting an exact copy. Paper patterns of each part should be made and fitted before cutting the metal. A knowledge of mechanical drawing, particularly the kind known as "Development of Surfaces" is useful to the worker in sheet metals, especially to the tinsmith who has to work out the patterns for new shapes.
Tin is made in such thin sheets that it is difficult to alter from its characteristic flatness by hammering, as one does with copper and pewter. Also its cheapness is such that the work of hammering is not war-ranted; since it is an established rule of craftsmanship that the more precious the material; the more work one is justified in spending; the reverse being equally true, that the cheaper or baser the material the less time one should spend on it. Tin must be treated very much like paper. If you wish to design for tin, you have but to work out the pieces in paper first, paste them together, bend them, curl them and twist them as you please. If you allow enough to paste the pieces together, say %" to that will likewise be sufficient for soldering the tin. Cut your patterns double. Then keep the pasted model and use the extra pat-terns for tracing the tin.
Curved frills radiating fanwise about the borders of candle sconces are put in with the wedge shaped end of a tinsmith's hammer, driving the tin into a carved notch in the end of a hardwood log. Their decorative quality is incidental to the fact that they are necessary to gather up the edges of the tin and draw them forward. Small convex bosses (such as feet for trays or candlesticks) can be driven out with a ball-pein hammer over little depressions in the end of the log.
The old pewter, so well-known in New England, displays a rare perfection of finish that is almost beyond the skill of the modern amateur, to whom all of the forms, moulds and special tools as well as the traditional training of the old craftsmen are not accessible. Nevertheless, his aim should be toward the acquiring of something of that skill. I do not mean that he should carry this so far as to produce work that shows no evidence of being made by hand at all; but he should aim at going beyond the ordinary summer camp production of hammered plates and ash-trays. The metal, being fairly costly, deserves to be-enriched by having a fair amount of labor applied to it in the working out of more complicated problems, such as pitchers, deep sugar bowls with fitted lids, hot water jugs, teapots, mugs and the like. A little chasing or engraving judiciously applied as a border may add a great deal to a piece that is already very satisfying in form.
We should keep a nice sense of fitness in expending our skill; not attempting to follow out the fineness of the goldsmith's art in dealing with a commoner material, but going rather for a freer, more rapid and exuberant style.
How TO SOLDER PEWTER
Fit the pieces to be soldered as closely as you can. Have both sides of the joint perfectly clean. Support the two pieces so that they stay together in the correct position and apply special flux to the joint. Take in your left hand a wire of special pewter solder, and hold in your right a bunsen burner or an alcohol lamp to which is attached a blowpipe. Blow gently and steadily, and focus the point of the flame on the end of the solder wire, which should be applied to the beginning of the joint. Bathe the surrounding metal gently with the flame until the solder melts and runs into the joint; and proceed along until it is finished. Never attempt to solder pewter with a soldering iron or ordinary solder.
Weigh out the metals and melt them in a ladle or small tin can. Bend a pouring lip in the can with the pliers. Then pour the metal into small grooves gouged out of a pine board. Don't forget to stir the metal well, and to skim it before pouring. Zinc chloride is made by dropping zinc into muriatic acid until the effervescing stops.
COPPER, BRASS, NICKEL SILVER AND STERLING SILVER
All of these metals are treated very much alike. They require annealing after they have been hammered for a little while. To anneal these metals make them red hot with a gasoline torch or over a forge, and plunge into cold water. The number of annealings on any piece of work should be as small as possible. Never attempt to anneal aluminum or pewter in this way because they melt at lower temperatures than red heat.
How to Solder or Braze These Metals
All of these metals may be joined with silver solder. Clean the joints thoroughly, coat them with a paste of borax or boric acid and water, support the pieces in the proper relationship and apply the heat. As the metal gets red hot lay strips of the silver solder against it. Or these strips may be set in between the pieces of metal before it is heated. Take care not to heat any part of the metal to a brighter color than the rest. This especially applies to brass, which may contain so much zinc as to make its melting point almost as low as that of, the silver solder. When the solder has run into the joint and filled it, allow the work to cool. Copper is usually brazed in-stead of silver soldered, because brazing spelter is much cheaper. The spelter is a low melting brass (about equal parts copper and zinc) used in the form of fine granules or filings. These are mixed with water and borax to a paste and applied to the parts to be joined. Then the work is heated as for silver solder.
The ordinary solder of commerce, known as soft solder, is usually made of equal parts tin and lead ("half and half"). It is suitable for joining tin, galvanized iron, zinc, and such articles of copper and brass as do not by their use or value warrant the trouble of hard soldering.
The usual tool is known as a "soldering iron," but it is never made of iron, always of copper. It is heated to about 600° F., which can be judged by holding it about 2" away from the cheek, at which distance it should feel fairly hot. Before it can be used the iron must be "tinned." The hot iron is rested against a rough piece of wood, and filed bright on one face. Immediately a piece of rosin is applied to the new metal and withdrawn. Quickly solder is rubbed on the point, and it flows promptly over the new surface of the copper. This is repeated for the other three sides of the point. Tinning must be renewed as it gives way to the black scum which forms while the iron is hot, especially if it is accidently heated to redness. Electric soldering irons are useful but do not hold much heat.
"Sweating" soft solder is done without an iron, in the manner described under pewter. Articles of brass, copper and tin may be wired together in the correct position, having first been thoroughly cleaned and fluxed, and heated to about 400 F. The solder wire is fed along the joint until it is complete. To be sure that the solder "takes" all over the metal you may, before sweating the parts together, "tin" all the surfaces to be soldered.
"Tinning" metals is accomplished in the following manner: (1) With steel wool or fine sandpaper rub up a strip on the edge of the piece to be joined. If the joint is to be sweated this strip can be the exact width of the joint. If it is to be done with the soldering iron, make it a little wider. (2) Apply flux to the clean strip. For galvanized iron use hydrochloric acid. For the other metals use the flux given, or a straight zinc chloride solution. Or use commercial soldering paste. Load the soldering iron with plenty of solder and run it along the fluxed area. If some areas do not "take," clean them again with the steel wool or emery cloth, apply more flux and repeat.
TO JOIN THE TINNED PIECES WITH THE SOLDERING IRON
Set them in their correct position. Place them so that pressure can be applied to the upper piece with a stick or the tang of a file. Then pressing firmly down, hold the soldering iron on the tinned part of the metal and melt the joint together. If the joint tends to spring apart, withdraw the iron and keeping up the pressure, allow each section to harden before going on to the next.
SHAPING BY HAMMERING IN A HOLLOW BLOCK
Let us for a simple example hammer a small bowl out of copper. Draw a 6" circle on a piece of 16--ounce copper and cut it out cleanly. Touch up rough places on the edge with a file. Now draw on the copper, concentric circles about %" apart. Your hardwood stump should have several saucer shaped depressions carved in the end grain, varying in diameter from 3/4" to 6" or more.
Method (1) : Put the center of the disc over the smallest depression and with your forming hammer drive the metal down into it (Fig. 27A). Move it to the next size and continue to drive the metal down until it takes the shape of the depression. These will guide its placing over the depressions. Move from the smaller to the larger until the copper has been worked right out to the edge. If the metal gets hard during this process anneal it. If the bowl is not deep enough at this point gather the edges up higher by the next method to be described.
Method (2): Hold your disc of copper at about 450 to the end of your stump (B) and touching with its edge the outline of the 3" depression. Drive the ball of your hammer lightly just inside the edge of the disc, forcing it into the depression. Rotate the disc as you go. When you have completed the circle you will have a little turned up rim, surrounding a flat bottom. Start another circle, striking on the next line 1/2" further in, and continue all around. By this time the outer edge may be crinkling a little. You must correct these crinkles by striking them with the hammer, filling in the space between the first and second circles with more blows. Your blows should be light but plentiful, rather than strong and few, and this applies to any kind of metal shaping. Continue inwards, using other depressions if advisable, until the whole disc has been worked. Then start again at the outside and draw it up further, repeating until it is as high as you wish, and annealing as often as required. These instructions apply equally to other metals (except, of course, that the annealing does not apply to pewter and aluminum). Some workers prefer to use pointed or rounded wooden mallets instead of the forming hammers, reserving the steel hammers for a final planishing (light hammering to refine the surface and give texture) when the shape is nearly finished.
How TO SHAPE COOKING VESSELS
It is time for someone to extoll the virtues of the tinned copper cooking vessels, for they are superior in many ways to the enamelware now in general use. A copper pot is practically indestructible. If hurled forcibly down on a concrete floor, it will receive a denting which can be taken out in a few moments with a hammer or mallet. But let an enamelware pot be dropped ever so gently and it is the recipient of an ugly bruise from which radiates a handsome series of line patterns. Between the lines are little chips of glassy material that eventually loosen and fall out, frequently in the food. A set of copper pots is an heirloom which can be passed from one generation to the next, but few enamel pots see more than two or three years' service, so that in the long run copper pots are much more economical. Add to this the rich and handsome appearance of the metal, and the quality of sentiment associated with things formed intimately by human hands.
Copper cooking vessels with flat bottoms and straight sides are either made in two pieces and brazed, or shaped over the stake from a disc. This is held over the stake with the edge of the stake under a circle that is drawn to represent the bottom. The projection to be turned up should not exceed about 3 1/2 ". Taller vessels are best brazed. Drive the metal down with a flat faced wooden mallet (C). Keep turning the disc until the circle is complete. The work will now resemble a ladies' straw hat with a floppy brim. Take up a steel hammer (D) and direct your blows against the junction of the "crown" and the "brim," forcing the brim to give way until the shape is all crown, keeping the work constantly turning. True up the bottom by hammering over a wide, flat-topped stake with wooden mallet, and flat-faced steel hammer or by laying the pot on a hardwood or iron block and working with the same tools from the inside.
The two-piece pots are made this way: Take a piece of copper of a width equal to the height of the pot plus about 3/4", and of a length equal to 3 1/7 times the diameter plus about 3/4". Make a kind of dovetail jointing in the ends and see that they fit neatly. Clean the metal around the joint, and bend your strip to a circular shape, fitting the dovetails into their proper places. Now holding the piece so that it does not spring apart, put it over a stove-pipe stake or a piece of heavy pipe clamped to the bench; hit the dovetails a few light blows with the ball of your hammer (E) to expand them and hold them from moving. Go along the joint tapping gently until it is fairly well closed. Apply a good coating of the brazing mixture on both sides of the joint, put it to the forge and braze.
File and scrape the surplus spelter from the joint. Put it over the stake and tip the end of the cylinder inwards for about 3/4", making a clean flange all round. With a sharp chisel cut another set of dove tails out of this flange. Then put the pot over a disc of copper cut for the bottom and trace the position of the dovetails in the bottom, and fit it, tapping the joint as you did for the side piece (F). Finally apply your paste and braze the joint.
When the joints are scraped clean you may planish the pot all over to true it up and enliven the surface. Then you have the question of handles. Single and double handles may be forged out of copper bars bought as scrap from your junk dealer. For the long handles (G) either make a wooden pattern and have them cast at the nearest foundry or buy some ready-made. Use at least two heavy rivets. They are started from the inside of the pot and riveted down over the holes in the handle, on top of a stake.
How TO LINE COPPER COOKING VESSELS WITH TIN
Copper cooking vessels must always be coated on the inside with pure tin to protect them against the acids of the foods, and to protect the foods against the poisonous compounds formed by the acids with the copper. These coatings are applied in this manner: First scour the pot free from all dirt, and boil in it a solution of lye or sodium carbonate to remove all grease. Then after rinsing, pour hydrochloric acid in it and move the acid around keeping it in contact with all the copper until it is bright, then pour out the acid. Now heat up the vessel on the forge and when it is quite hot pour into it a small quantity of pure tin, that you have melted and skimmed in a little ladle. Rub it briskly into the copper with a handful of clean waste. The copper will have to be evenly heated all over to get the best results. If part of the copper refuses to take the coating of tin, rub it with a piece of sal ammoniac (ammonium chloride) continuing to rub with the waste. Add more tin, if necessary, until the coating is smooth, thick and even. The coating should last several years in constant use, but as soon as it does show sign of giving way and exposing the copper, it should be promptly renewed.