SOFT SOLDER—SHEET TIN—THE PROCESS OF SOLDERING—HEATING APPARATUS—ELECTRICAL SOLDERING COPPERS—THE COMMON SOLDERING COPPER—FLUXES—TINNING THE COPPER—HEATING
Soft Solder.—When two or more pieces of metal are joined together with a metallic cement, they are said to be soldered.
Sheet tin, of which cans are constructed, is always soldered with soft solder, a mixture of lead and tin, usually 50 per cent. lead and 50 per cent. tin.
This solder is usually supplied in wire or bar form at any hardware or electrical supply house.
Copper, brass, bronze, iron, silver, gold, and practically any metal except aluminum may be soldered with soft solder.
Sheet Tin.—Sheet tin, so-called, really consists of a thin sheet of iron coated on both sides with tin. This coating of tin serves several purposes. It enables the solder to adhere easily; it prevents the iron from rusting; and when the sheet tin is made up into can form, the tin coating protects the contents of the can from chemical action on the iron.
The Process of Soldering.—Soft solder is applied to the metal to be soldered in a molten state and this operation requires considerable heat. When heat is applied to metal it usually oxidizes that metal; that is, dirties it.
Solder will not adhere to oxidized metal. The metal must be protected with a coating called a flux while being soldered. Soldering paste, soldering fluid or “killed acid,” resin, paraffin, heavy oils, and vaseline all serve as fluxes, some better than others. The soldering paste is by far the best, as will be shown later.
Soft solder is applied to the tin, on the point of a hot soldering copper, often wrongly called a “soldering iron.” A soldering copper consists of a pointed bar of copper suitably fixed to an iron shank which is firmly set in a wooden handle. The point of the copper must be well coated with solder or “tinned,” so that when it is heated it will pick up the solder and convey it to the joint to be soldered.