Water-jacketed Cupola
The Encyclopedia of Founding (1892)
The Keims cupola is jacketed, and is described by the inventor as follows: In this new cupola there is no burning out at or about the tuyeres; there are no clinkers to be chipped off daily, and repairs to be made before another heat can be run; and the bottom need not be dropped for months, if you so desire. To accomplish these results the inventor uses a three-foot water-jacket, with the tuyeres placed as near the bottom of the jacket as possible; the blast being upward, and the jacket not allowing anything to adhere to it, prevents burning out or clinking. The lower portion is part and parcel of the jacket (but not water-jacketed), and is lined with fire-brick, so as to retain the heat in the metal well and to prevent chilling. This improved bottom and jacket may be used in connection with the old cupolas now in use by simply taking off enough of the bottom of the old in which to insert the new, thus avoiding any great expense in making the change. As there is no hanging or clogging in this cupola, the blast has perfect circulation throughout the entire mass that is to be melted, and so is a great fuel-saver, as every particle of fuel is used to the best advantage. As the heat of the jacket cannot be raised above 240 deg. Fahrenheit, it will readily be seen that there will be no burning out, and that with ordinary care a jacket will last as long as a steel boiler; for the whole arrangement is made of 1/4-inch steel plate, and as the overflow is higher than the jacket, it would be only through gross negligence if it should burn. In fact, the jacket would be the coldest point as long as any water remained. The metal produced is of the best quality, and has a ring almost equal to bell-metal.
What Has Changed in the Last Century
When The Encyclopedia of Founding printed Keim's own sales pitch in 1892, the water-jacket was a novelty bolted onto existing cupolas to stop the shell burning through at the tuyeres. The idea itself won: by the mid-twentieth century water-cooled, and often lining-free, cupolas were standard in large iron foundries, running continuously for weeks rather than needing the bottom dropped after each heat. What has gone is the cupola's dominance. Coreless induction furnaces took over most iron melting from the 1960s onward, and air-pollution rules from the 1970s, which demanded afterburners and bag-filters on the stack, closed many of the small cupolas Keim was selling to; the survivors are mostly big continuous units, plus the cupolas that melt rock for mineral wool.
Written for this edition, 2026.