The above is the mode of casting usually practised in England ; but various modifica tions of the processes have been brought into Ise in Edinburgh and elsewhere.
Stereotype plates need careful examination md picking, to remove the imperfections in he casting. Small hollows, such as the loops 3f an a, an e, or an o, are liable to be filled up vith metal, owing to blebs of air in the mould, ind the fine white lines in wood-engravings tre sometimes filled up. Such matters should to corrected by the picker, who should also rut down, with suitable tools, such blank ;paces as might be liable to soil in printing. Before printing also, defective letters or words vhich cannot be corrected by the picker should to cut away, and types inserted in their place. these types are soldered into holes drilled ,trough the plate ; their stems being sawn off lush with the back.
Although the plates are cast of as equal a ,hickness as possible, they require, before printing from, to be accurately flattened at he back by means of a peculiar kind of lathe, n which a steel cutter, or knife, mounted in slide-rest, shaves off the metal from the back of the plate in concentric circles, until it is made perfectly even. They are then mounted upon blocks of wood or metal, to raise them to the same height as common types. The tendency of wood to warp when exposed to changes of temperature, or to oc casional wetting, has led to many projects for mounting stereotype plates upon blocks of cement or upon metallic mounts which might be applicable to plates of various sizes. When
wooden blocks are used, the plates are usually secured to them by clips at the edges, and sometimes by screws.
The process of stereotyping is one of the most important means by which the produc tion of cheap books has been facilitated of late years. For a work of limited and tempo rary demand it is unnecessary; but where the demand is very great, and likely to last for several years, it is all-important, since it enables the publisher not only to provide for the regu lar sales, hut also to meet, on short notice, ex traordinary demands for the work caused by peculiar circumstances, without the expense of having a very large edition printed at once. In most cases where the demand is uncertain, and in almost all where the demand is sure to be large, it is desirable to resort to stereotyping, because, although it increases the first cost of production, it enables the publisher to avoid, on the one hand, the risk of printing a great num. ber of copies which may prove unsaleable, and, on the other, the outlay necessary for the re composition of the types, in case the demand should exceed the number of copies first printed.