Printing on Celluloid.

Some of our readers (says the Printing Times) have doubtless seen pleasing specimens of engravings printed on celluloid or xylonite plates, but they probably do not know that there is difficulty in securing satisfactory and permanent impressions with this material. This difficulty, independent of the expense of engraving, has necessarily made the plates costly; but it is claimed that it has been overcome with a new process of printing by which the celluloid or pyroxyline compound is subjected to the action of heat and pressure while in contact with the engraved plate. The process is thus described in the American Stationer:—

In carrying out this process it is deemed advisable to use an ink which will exert under heat and pressure a softening or penetrating action upon the pyroxyline surface, so that the coloring matter it contains will be forced into or effectually attached to the material. Any ink that contains a solvent of pyroxyline may be used, but the employment of an ink in which the coloring matter is in the form of a pigment, and which also contains a binding agent for holding the particles of pigment together, is recommended. The printing is performed by preference with an ordinary engraved plate, and one having a highly-burnished surface, and it is said to have been found practicable to make use of plates in which the lines are of the most delicate character, and also plates having plain surfaces, the design being transferred or applied thereto in any similar manner.

If an engraved plate is to be used, it will be inked and made ready in any convenient way according to the method of the engraver's art, and, when desired, placed in contact with the pyroxyline surface to be printed, and the latter subjected to heat and pressure, the heat to be from 180° to 230° Fahrenheit, and the pressure sufficient to cause the material to flow into the engraved lines, which will be continued usually for about a minute, the heat and pressure being preferably applied to the material through the plate.

In printing upon sheets or other thin pieces of material, the sheet to be treated is placed in what is known as a « steam-table press, » with the surface of the sheet that is to receive the impression in contact with the ink surface of the plate, and the heat and pressure are applied as specified. If the sheet of material is exceptionally thin, it will be desirable to back it up with a layer or layers of blotting-paper, or other elastic material, for the purpose of preventing or correcting inaccuracies which are likely to be caused by any inequalities in the plate or the sheet, and to prevent the sheet from adhering to the backing, a layer of any non-adhesive substance—such as metal or tinfoil—may be interposed.

In treating thick sheets or pieces of material there is danger of the heat and pressure causing the material to flow, which will cause the impression to be blurred or distorted. This danger is obviated by using a die or mould which conforms in shape to the thick sheet or piece which is to receive the impression, in which the material is closely and compactly fitted, so that its shape will not be affected by the heat and pressure, and the displacement of the surface to be printed on will be prevented. Any die or mould which will prevent a change in the surface which carries the impression may be made use of.

The printing may be accomplished in any other substantial manner, the essential consideration being the use of heat and pressure. By applying heat, the surface of the pyroxyline compound is softened, and, by means of the pressure exerted thereon, the material is caused to flow into the engraved lines in the plate. By this means it is said that results can be produced upon the material used which are in every way equal to those produced upon paper. The process is patented.