Fig. 3.
From a purely mechanical point of view the construction of the copperplate press ([Fig. 3]) is of an exceedingly simple character. Its primary purpose is to produce a heavy and uniform pressure on the plate during operation.
After being charged with a special pigment and cleaned as hereafter described, the plate is laid, face upwards, on the iron bed or table of the press and in contact with the paper, and passed through between two iron cylinders. These cylinders are so adjusted as to produce an exceptionally heavy pressure. Such are the simple elements of a process which, however, requires much closer investigation.
In its application to lithography the following are the only requisites for copperplate transfer printing.
A stick of prepared transfer ink—whiting, free from grit—transfer paper, and a plentiful supply of soft rags. Likewise, an iron plate with a gas jet underneath ([Fig. 4]), a square of printer’s blanket, and a damp book consisting of twenty or thirty sheets of blotting or other absorbent paper slightly and uniformly damped.
Fig. 4.
A good copperplate transfer paper can be made according to the recipe given in [Chap. III.], but unless a fairly large quantity is used the commercial qualities will be found most economical.
Copperplate printing, in its application to lithography, is a simple operation, but it requires extraordinary care for its successful execution. The conditions under which lithographic transfers are made from a copperplate engraving are vastly different from those which control copperplate printing for ordinary purposes of reproduction.