Silver is also a metal of history. The ancient Greeks knew of it as the metal electrum, an alloy of gold and silver, of a brilliant pink-whiteness. Silver is now used largely as a silver-gold or silver-copper alloy, in which the gold or copper is present in approximately 10 per cent. Only rarely is the pure metal used, as for filigree work or for alkali retainers.

Pure silver melts at 960 deg. Cent., and is commonly placed second in tables of ductility and malleability. It does not oxidize in air when heated. All of these qualities point to the supposition that it is readily weldable. But though pure silver is made into filigree work, it is always soldered. The common alloy for jewelry being a combination with copper would suggest at once that soldering or brazing is necessary. In recent years, however, silver has been successfully joined in the electric welder, both to itself and to other metals. Because of its high heat and electric conductance it requires more current, as is also the case with copper.

1 "The Goldsmith's Handbook," G. E. Gee, p. 136.

The joining of silver to silver is effected in jewelry shops with a mouth or gas-air blowpipe and with fine silver as a solder. Other solders are alloys of silver and copper; silver, copper, and zinc; and silver, copper, zinc, and tin. These alloys are given in order of their melting points, the most refractory first. The flux is borax.

It would be well to bear in mind that tin is even more harmful to the working properties of silver than it is to gold and aluminum. Even fumes of tin will alloy with silver and make it brittle. For this reason tin should not be used in solder.