CHAPTER IV. PRINTING FROM THE BLOCK.
A half-tone block to give results commensurate with the care needed in its preparation, must be handled by the machine man with care and consideration.
The blanket on the tympan or cylinder must be replaced with something harder, else the soft pressure of the blanket will blur the print.
The block must also be made ready, not by putting cut-outs on the tympan or cylinder, but underneath the block, and there as thin as possible.
The ink must be good and not too thin; the rollers must be free from flaws and not too tacky. In fact, as much care is required on the press as during the photographic and subsequent operations. Indeed photo-engraving and zinc etching would have come into popular use more rapidly than they have, if printers had been willing to give them the special “making-ready” attention they require. Despite all prejudice and indifference, “process-engraving” so called, has made continuous improvement ever since it came into use, and the good work goes on. The most delicate gradations of light and shade discernible in nature, may, from the photographic plate, be rendered in pure black and white by means of any of the methods given in this work. All that nature displays, and all that imagination compels, may be reproduced indefinitely.
With regard to the storage and keeping of zinc blocks after using, Mr. T. Bolas, in the Photographic News of September 24, 1886, says, “they should not be washed with the usual lye, but should have a few drops of paraffine oil poured upon them; and after this has been well rubbed in by a soft brush kept for the purpose, the paraffine should be well wiped away with a soft cloth. If the block is to be stored away for a long time, it should be waxed. The best way of doing this will be to make it rather warmer than is necessary to melt wax, and then to rub it over with a piece of yellow bees’-wax, after which the excess is wiped off with a piece of flannel.”
Sometimes zinc blocks are electroplated with copper or nickel (a necessity when they are to be used for certain color work), and such blocks should also be treated in the same way as the bare zinc, as they cannot be safely cleaned with the lye solution.