When, from an original of black lines on a white ground, it is desired to make a reverse block—i. e., white lines on a black ground—a negative is first made from the original, and from that negative a transparency is made; and a print made upon the zinc from that transparency will be a reverse of the original.
Thus far I have tried to make plain the details of a process which is as fascinating and as pretty as any in photography, and which supplies results which could not be attained by the most expert workers two years ago. And since those experts first obtained even tolerable results by zinc etching, like {62} everything else in photography, it has made wonderful progress. At first we were delighted and content when a block was obtained with relief sufficient to enable us to print it upon an ordinary press with type. But now we can get from the zinc surface all the qualities which are given by the lithographic stone. Indeed, the process of zincography bears a very strong general resemblance to that of lithography; of course, it varies therefrom in matters of process detail. The manipulations of zincography, however, are no more complicated in their nature than the details of printing, etc., from stone. Crayon drawings, ink work in line and stipple, rubber work, in fact, anything that can be drawn on stone can be drawn on properly prepared zinc, with the exception of engraved lines (intaglio), the structure of the zinc not giving the yielding brittleness of stone. The great departure made possible by zinc plates exists in the fact that they can be bent to the surface of a cylinder, thus displacing the reciprocating bed and stop-cylinder of the lithographic press with the continuously rotating plate and impression cylinder of the zincographic press, which, at the same driving speed, produces double the number of impressions printed on the lithographic press. To Mr. Bernard Huber, of the Huber Printing Press Company of Taunton, Mass., belongs the credit of designing the only American zincographic press in existence, and which is now in successful operation in several lithographic establishments. It is a thoroughly American machine in design and construction, and while no glowing prophecies of its immediately taking the place of lithographic presses are indulged in, yet this kind of press has its place and use, and will by its qualities win favor in the trade.
Many lithographers are beginning to give correct attention to zincography, but few are willing to give the time and constant experimenting to the subject that has been given by Messrs. Harris & Jones, who during the past three years have operated the zincographic presses in their lithographic establishment known as the Providence Lithograph Co. Having taken the selling agency of the Huber zincographic press, they offer to those who buy the press full instructions in zincographic surface printing.
These suggestions are given right here, first because we are now about to take a step higher in zinc etching—a step which will lead us to results which lithography can scarcely equal in some particulars—and second, because it is the policy of this work to withhold no information which the novice will need in supplying himself with a perfect outfit for doing the best of work. For the same reason the advertisers have been chosen, rather than received in the usual way.
PART II. PHOTO-ENGRAVING IN HALF-TONE.
CHAPTER I. RETROSPECTIVE.
The former chapters have treated entirely upon the production of blocks in line—i. e., where the picture has been made by a draughtsman, the half-tones and gradations being communicated by a greater or less thickness of line, or by dots, or stipple, or hatching.
The picture for such blocks may have been specially drawn for the process, the same size or larger, or it may be a copy of some woodcut or engraving already in existence, but if it is desired to reproduce blocks from drawings, paintings, or photographs, then an entirely different method must be adopted, and the smooth gradations of half-tone levelled, so to speak, so as to bring the high lights and the shadows upon one plane.
In photographs from nature (or from washed drawings or paintings) the scale of gradations runs, as it were, in a series of short steps from the deepest shadow to the highest light, and a block made, say in bichromated gelatine, from such a negative can give no half-tones, as the inking roller could only touch the deep shadows properly.
Now the subject of making photographs applicable for the illustration of letter-press, instead of woodcuts, has occupied the attention of experimentalists from the early days of the art-science, as the records of the Patent Office show.