Printing

Moulding.—The face of the forme is then carefully brushed over with oil, the open spaces between the lines being packed with card or pieces of thin metal to prevent the cracking of the flong when moulding. A piece of the damp flong about an inch larger all round than the surrounding bearers is placed face downwards (tissue side) on to the forme and, by means of a stiff brush with a long handle, is beaten by hand evenly into the type until a uniform depth is obtained. The "blanks" (de pressions) on the back of the flong are then filled in with felt or card and covered with a strong sheet (usually brown paper). Both the forme and the flong are then placed into a drying press, being kept under pressure until the flong is baked dry. The flong is then carefully removed from the forme and becomes known as a matrix, or, as the stereotyper calls it, a "mat." This is then trimmed, and a long piece of brown paper, called a "tail," is pasted on to one end. The latter acts as a guide to lead the molten metal on to the face of the matrix when the plate is being cast.

Casting.—The matrix is then placed in a casting box which consists of two flat surfaces, the top part being hinged so that it may be thrown back in a perpendicular position. When the matrix is placed in the box it is held in position by two steel gauges which not only determine the thickness of the plate but prevent the molten metal running out at the bottom and sides of the casting box. When the matrices and gauges are correctly positioned the top is lowered and clamped to the lower surface. It is then tightly secured by means of a screw, the whole of the box being tilted into a perpendicular position. The mouth of the box is bevelled to allow the molten metal to be easily poured in. This is done by means of a ladle. A few moments are allowed for the metal to set. When the box is opened the gauges are removed and the matrix relieved from the newly cast plate, the casting operations being repeated from the same mould according to the number of stereo plates required. The plate has then to go through a series of finishing operations to put it in a proper condition for printing. The plates are mounted on a block of wood to bring the printing surface to type height.

Newspaper and Periodical Printing.

It is in newspaper and magazine production that stereotyping has made the greatest progress. Speed is essential in these particular branches of print ing, and instead of a wet flong a special manufacture of dry flong is used, the matrix being moulded either by cylindrical pressure, usually known as a "mangle," or by means of a special press on the platen principle. The matrix is then dried and when thoroughly free from moisture is placed in a casting box which is lialf cylindrical in form and conforms to the diameter of the cylinder of the printing machine on which the plate is to be printed. Metal is then pumped direct from the metal pot into the casting box. When the plate is cool it is removed from the

box in a semi-circular shape.

Automatic Casting.

The ever-increasing demand for speed and accuracy in the production of newspapers has brought into general use an ingenious machine called "the Autoplate." This is an American invention, capable of producing two plates in a minute in place of the one plate in three minutes, which was the usual time taken to cast a plate when the work was done by hand. On the Autoplate the matrix is fixed into clips and carried to the casting box, which, when closed, is flooded with molten metal pumped from a large metal pot. After a short "dwell," the casting box is opened and the plate removed from the matrix, the former being cooled by a system of water circulation. The plate is then mechanically bored, routed and finished, ready for the printing press, every operation being automatically controlled.

A later development in the automatic casting of stereotype plates is the invention of a Swiss engineer and is known as "the Winkler." In this instance, a "perfect plate" is produced without resorting to the usual finishing operations. The metal pot is directly connected with the casting box and the weight of the metal in the pot provides the necessary pressure to cast a large sized plate without leaving surplus metal to be trimmed off. This machine produces two finished plates per minute.

Electrotyping.

Electrotyping is an electrolytic method of producing a duplicate printing plate. In this process a mould from the original is taken in wax or prepared lead, on which a coating of copper is electrolytically deposited.

When Volta invented the galvanic battery in 1799, the foun dation of the process was laid. About 1839, two Englishmen (Thomas Spencer, of Liverpool, and C. J. Jordan, of London) and Prof. Jacobi, of St. Petersburg, were experimenting with the making of plates by the science of electrometallurgy. About the same time, J. A. Adams, a wood-engraver in New York, is credited with having made an electrotype, which was used for printing in 1841; this process he also used for duplicating illus trations for Harper's family bible, which was issued between 1842 and 1844. To obtain a mould he used a soft metal. About 184o Smee's battery was introduced, making the deposition of copper a commercial proposition. About this date graphite was first used to make the surface of a mould made in beeswax conductive. A French cabinetmaker, M. Victor Morel, took a prominent part in improving the process for printing purposes. He was ultimately engaged to install a foundry in the establish ment of Cassell (London). Electrotyping owes a debt to this publishing and printing house for the experiments they made at great cost, with a view to perfecting the electrotyping process. Beeswax as a moulding medium was first used by them.