Brazing
2 of the 6 encyclopedias on this shelf carry an entry for Brazing. Both are reproduced below, so you can see where they agree and where they differ.
The Encyclopedia of Founding (1892)
Soldering with an alloy of copper and zinc. This operation is usually confined to joining copper, zinc, and iron surfaces, and in order to effect a solid junction the surfaces to be united must be made clean and bright. The brazing alloy, after being granulated, must be wetted with ground borax and water and then dried, after which it must be strewn over the gap or crevice, or between the two pieces to be united, which are then exposed to heat until the solder flows between them. The solder may be rendered more fusible by the addition of a little zinc. See SOLDERING; SOLDERS; CAST IRON TO BRAZE. Breast-hole is the hole in front of the cupola, just back of the spout, at which place the tap-hole is formed. Much of the trouble caused by slag gathering at the tap-hole is attributable to the very careless manner in forming the tap-hole. Sand is used for this purpose without reference to its refractoriness, the consequence being that the intense heat gradually melts it into slag, and it issues from the hole at every tap. If the heated fuel in front is made as level as possible, filling all the spaces with pieces of coke before the sand is introduced, and no more than about three inches of a well-dampened and refractory mixture be rammed therein, much if not all of the trouble from slag at that point will cease. See CUPOLA; SPOUT; SLAG; TAP-HOLE.
Collier's New Encyclopedia (1921)
the act of soldering together the surfaces of iron, copper, brass, etc., with an alloy composed of brass and zinc, sometimes with the addition of a little tin or silver.
What Has Changed in the Last Century
The 1892 Encyclopedia of Founding described a single trade practice: granulated copper-zinc spelter, wetted with borax and water, strewn into the crevice and heated in the forge until it ran. That recipe still works, and borax is still sold as a brazing flux, but brazing is now defined by temperature rather than by alloy about 450 C (840 F) is the accepted line separating brazing from soldering and the filler metals have multiplied to include silver-copper-zinc alloys, copper-phosphorus for copper pipe, nickel alloys for jet-engine parts and aluminium fillers used with fluxes that let car radiators and heat exchangers be brazed by the million. Heating has moved off the open fire into gas-shielded and vacuum furnaces, induction coils and molten-salt dip baths, which produce joints clean enough to need no pickling afterwards. One health change the old books could not have anticipated: cadmium, long added to silver brazing alloys to lower their melting point, has been largely driven out of general use because its fumes are toxic.
Written for this edition, 2026.