The lasting quality of a copper range boiler as compared with an iron one, when used to heat hard water, is not worth the extra cost. The incrusted deposit that is the usual cause of boilers becoming destroyed in hard-water districts will make the copper plate fracture nearly as soon as it will the iron. An idea is prevalent that by using a copper boiler the accumulation of deposit from hard water, and subsequent fracture of the boiler, are prevented or avoided, but this supposition is groundless: a copper boiler is at no real advantage in heating hard water. In soft-water districts copper is largely used because iron will not long withstand the active rusting process that the soft water sets up. In such places copper boilers, copper cylinders, and lead, copper, or tin-lined pipes have to be used. The thickness of the plate of copper boilers varies, for copper being such an excellent wearing material (when water is in close con-tact on one side of it), the plate need not be thick, and 1/4-in. plate would be ample if it were not that copper is soft and cannot withstand heavy water pressure, nor the blows that the cook delivers against the boiler front with the poker.

Therefore the usual thickness is 5/16-in. body, with 7/16.-in. or 1/2-in. front-plate. If the boiler is large, and the water pressure exceeds, say, 40 ft., then either a thicker body-plate must be used, or brass stay-bolts must be placed across the body-plates. Brass or copper bosses must be brazed around the pipe holes, to allow of a sound joint being made; and, in hard-water districts, it is important to remember to order a manhole large enough to insert the hand for cleaning. A 3-in. hole and a 3-in. plug are usually sent to make the manhole and lid, but this is too small. The cost varies with the market price of copper, but the boilers are usually something under Is. per lb. Copper boilers, before they get beyond repair, should have a piece dovetailed in and soundly brazed.