The hot copper, charged with solder, is passed slowly along the joint and as the tin to be soldered receives enough heat from the copper, the solder leaves the copper and adheres to the tin, firmly uniting it.
Heating Apparatus.—Some form of heating apparatus is necessary to heat and maintain the soldering copper at the melting or flowing point of the solder. The copper may be heated in a gas furnace especially made for soldering coppers, or over an ordinary gas stove burner or a common blue flame oil stove, or a charcoal fire, a wood fire burned down to embers, or a plumbers’ gasoline torch, but never in a coal fire. Coal contains too much sulphur which oxidizes the copper and renders it useless for soldering purposes.
The Blue Flame Oil Stove.—For heating the coppers in my country shop, I use a blue flame oil stove, one of the less expensive sort, with the asbestos ring wick and the short removable chimneys. The stove has two burners and will heat from four to six coppers at once. The flames may be regulated nicely so as to give just the required amount of heat and this stove consumes very little kerosene, and, therefore, costs little to operate. In [Fig. 16], it will be noticed that there is a curved hood over each stove hole. These hoods may be easily made from part of a large can or of a piece of tin or sheet iron bent into shape. These hoods conserve the heat and throw it about the coppers. I also place a piece of heavy wire netting over the grating of the stove holes to support the coppers and to permit their being laid to one side, out of the intense heat, when not immediately needed.
The blue flame oil stove forms the most satisfactory arrangement for heating coppers that I have ever used in the country. These stoves are easily taken care of and are understood by almost everyone. The directions should be nailed up alongside the stove and carefully followed, particularly as to cleaning the burners once or twice each season.
Fig. 16.
The Gasoline Torch.—The plumbers’ gasoline torch is often used by experienced metal workers for heating coppers. In inexperienced hands, this torch is rather a dangerous affair. Only one copper may be heated at a time and it is difficult not to overheat the copper in the fierce roaring flame. The cost of the torch and the cost of operating it are both greater than the blue flame kerosene stove. However, in experienced hands, it is safe enough and very useful about the shop. In using such a torch the directions should be most carefully followed; all joints, filler openings, etc., must be airtight when operating or a disastrous fire or explosion may result. The tiny jet opening in the burner must be kept clean.
The Gas Furnace.—In my winter shop in the city where gas is available, I use the gas furnace shown in [Fig. 16]. This is a most satisfactory and widely used heater for soldering coppers, as it gives an intense blue flame that may be easily regulated.
When using a heater of this sort, one must be sure that it is lighted correctly or a smoky yellow flame will result. To produce a blue flame, air must be mixed with the gas; just as it is in a bunsen burner or an ordinary gas stove, for that matter. Gas is admitted to the furnace through a small nozzle at the end of the mixing flue near the rubber hose connection. Air is admitted in the slot under the gas nozzle; a movable slide encircles the mixing flue over the slot to control the amount of air admitted. This slide must be tightly closed over the air vent when the gas is first turned on.