ROLLER, used as part of the inking apparatus in letter-press printing, is of modern invention. In the old process of applying the ink to the surface of types, stuffed leather balls were made use of, which were not only difficult to keep in proper order, but were inapplicable to cylinder-printing. The first improvement on the stuffed balls consisted iu covering them with a soft and elastic composition, such as was employed in the Staffordshire potteries. Catching at this idea, the inventors of cylinder printing +machines made rollers by coating longitudinal and rounded pieces of wood with the composition, by means of casting in a mold. This invention came generally into use. between 1814 and 1818, everywhere superseding balls, and rendering printing machinery 'practicable.
The method of is very simple. A roller may be of any length, to suit work of different kinds; for hand-presses it is usually about 30 in. long, but longer for machines. according to their dimensions. The thickness is about 3 in., of which the composition on the wood is probably three-quarters of an inch all round. The wooden center being fixed upright in an iron mold, the composition is pbured in when in a hot liquid state. and then left to cool. When cold, the mold, whicli is in
halves, finely-jointed and held together, is opened, and the roller taken out: by a little trimming it is ready for use. The composition consists of a due proportion of fine glue and treacle or molasses, boiled together, and thoroughly blended—the result being a substance resembling soft india-rubber. The proportions of the two ingredients depend -on the state of the atmosphere. In summer, one pound of glue to one pound of treacle may form a suitable but in winter it may be requisite to give three pounds of treacle to one pound of glue, in order to insure the proper elasticity. Rollers, in time, :shrivel and waste by use, and the composition may then be remelted, along. with some 'small addition of new materials. In' all cases, the rollers require to De kept very clean,. and suspended in a rack when not in use. The manufacture awl supply of rollers for printers constitute' a distinct business in London; but elsewhere, as far as we know, every printing establishment of any consequence possesses means of fabricating rollers for itself.