When a broken pane is to be replaced in a window, it is done generally without taking out the sash; but in the case of glazing the sashes of a new house, such as we have been supposing, it is done before the sashes are fitted into their places. If sashes are glazed with plate instead of crown glass, the only difference in the glazier’s method of proceeding is, that the pane being heavier, must be fixed in with greater attention to security. Sometimes a small beading or fillet of wood is used instead of putty, in which case it is either nailed or screwed to the sash.
Where skylights are used instead of windows, a different plan must be observed, since there are no cross bars to the sashes. In this case the squares of glass are fixed in somewhat in the way adopted in slating a roof, that is, the lower pieces are puttied in first, and the upper ones are lapped over them, so that each pane projects about three-quarters of an inch over the one next below it. This is to effect two objects,—to prevent the necessity of puttying the joints, and to exclude rain.
Ground, fluted, painted, stained, and embossed glass, are occasionally employed for windows. These need not be noticed, since the processes by which they are fluted, stained, &c., would carry us to details of too extensive a nature. So far as the glazier is concerned, rather more care and delicacy are required in proportion as the kind of glass employed is more costly or more ornamental.
In some of the better kinds of houses, rooms are provided with double windows, separated a few inches from one another. The object of this is, to prevent the room from being affected by rigorous cold from without; for a mass of air when stationary, conducts heat very slowly; the stratum of air between the two windows, therefore,—being stationary,—is slow to conduct the cold from without, or, more correctly, to conduct the warmth from within.
Sheet Lead for Roofs and Cisterns.
Whether the glazier precedes the plumber or the plumber the glazier, or whether the labours of both alternate during the building of a house, is a question of no great importance to our present object. We will therefore proceed to notice the kind of material employed by the plumber.
The comparative cheapness of lead, its admirable qualities, and the facility with which it can be cast and rolled into thin sheets, and drawn into pipes, cause it to be extensively used in building. The most productive mines of this metal in our own country are situated in Derbyshire, Devonshire, Cornwall, in Wales, and in the North; in short, the ore from which lead is generally obtained, called Galena, or Sulphuret of Lead, is found in all countries where the primary rocks appear at the surface. The ore greatly resembles the pure metal in brilliancy; but it is brittle, and not so easily fused. It frequently contains a sufficient quantity of silver to make it worth while to adopt a peculiar process in the reduction of it, in order to separate this more valuable metal. The ore is first broken into small pieces, and is then roasted in a reverberatory furnace, to drive off the sulphur. When this object is attained, the heat is increased, till the metal is fused, and then it is drawn off into moulds, which give it the form of blocks or slabs, called sows and pigs.
Sheet lead is made thus:—A large furnace is provided, into which pig-lead is thrown, and heat applied. When the lead is melted, a valve or cock is opened in the side of the furnace, and the glistening liquid metal pours forth, and falls on a large table, covered over with an even surface of fine sand, and having a ledge of an equal height above the sand all round it. When the melted metal is poured on the sand, two men, holding each end of a stiff wooden rule, called a strike, draw it along the table, resting on each side ledge: the liquid lead is pushed onwards by the strike, till it covers the whole surface of an even thickness, which of course is governed by the depth of the ledge round the table.
Milled sheet lead is formed by rolling a cast plate of the metal between large iron rollers, turned by machinery. These rollers are set closer and closer together, till the lead is reduced by rolling to the requisite degree of thinness. By this process, the lead is rendered more dense and more equally so, than it ever is by simply casting: milled lead, consequently, is more durable than cast-lead.
It should be here noticed that lead, when it is used for roofing, or for lining cisterns and gutters, is always laid on an even boarded surface, and not on battens or laths, like slate and tiles.