A peculiarity of Monotype composition is that, while the keyboard produces the perforated roll in the usual sequence from beginning to end of the story, the casting machine reverses the process by starting at the end of the composition and finishing up with the beginning.
The metal used for casting type is a mixture of lead (five parts), antimony (two parts), tin (one part), and sometimes a small addition of copper. Lead forms the chief part of all type metal, as it melts easily and fuses readily with other metals; but lead alone is too soft for the service required of type. Antimony is brittle and gives hardness, and tin is added to impart toughness. Lead and antimony in approximately these proportions make an alloy which has the unusual quality of expanding slightly, instead of shrinking, when cooling, thus permitting a full, sharp cast in all parts of the mold. Tin flows readily when melted and increases the smoothness of the cast on the surface of the mold. A small quantity of copper may sometimes be added to give still greater toughness.
The metal used for small sizes of type is commonly harder than that used for the large sizes, the softness of the metal gradually increasing with the size of type made. Script types and faces with delicate lines are usually cast with metal a little harder than that used for the normal and bolder faces.
The foregoing refers more particularly to type cast by the regular foundries. The metal used in automatic casting machines, like the Monotype, contains a larger proportion of lead and less antimony; while the metal used for casting line-slugs in the Linotype machine is composed of still larger proportion of lead and very little of the other two metals. Stereotype metal and metals used for leads, slugs, furniture, etc., are largely lead.
Large types, such as are used for posters and large bills, are made of wood. The smallest size for practical use is 48-point, or 4-line pica. Sizes of wood type are multiples of the pica, and are so named, as 8-line, 10-line, etc. They are much cheaper than metal types, though not as durable or satisfactory for printing. The wood commonly used is maple, and the letter is made on the end of the grain. It must be well seasoned and polished. Pine and other soft woods are used for very large sizes of wood type and poster engravings.