This method of making the blocks is more complicated. As there are no lines in a wash drawing, or in a photograph from nature, or in a painting, it is necessary to obtain some kind of grain, or interstices of white, on the zinc plate, as in a mezzotint; so between the drawing or photograph to be reproduced and the camera, glass screens covered with lines or dots, are interposed, varying in strength according to the light and shade required; thus turning the image of the wash drawing or photograph practically into “line,” with sufficient interstices of white for printing purposes.
The coarseness or fineness of grain on these blocks varies according to circumstances. Thus, for rapid printing on cylinder machines, with inferior paper and ink, a wider grain and a deeper cut block is necessary.
The examples in this book may be said to show these process blocks at their best, with good average printing. The results from wash drawings, as already pointed out, are uncertain, and generally gloomy and mechanical-looking.
The reproductions of pencil, chalk, or charcoal drawings by this process are generally unsatisfactory, even when printed under good conditions. The blocks are shallow as compared with the zinc line process, and are double the cost.
INTAGLIO PROCESSES.
PHOTOGRAVURE, AUTOTYPE, DALLASTYPE, ETC.
Photogravure.—First, a photographic negative is taken direct from the picture to be reproduced, and from this an autotype carbon print is taken and transferred on to glass or silvered copper, instead of on the paper used in making carbon prints for sale. This picture is in delicate relief, and forms the mould, upon which copper is electrically deposited. After being made “conductive,” the carbon mould is placed in a galvanic bath, the deposit of copper upon it taking the impression perfectly.
Another method is to transfer the same mould upon pure, clean copper, and then operate with a powerful biting solution, which is resisted more or less according to the varying thickness of carbon mould to be penetrated. Thus the parts to be left smoothest are thick of carbon, and the parts to be dark are bare, so that the mordant may act unresisted. This, it will be perceived, is the opposite way to the process above given, and is therefore worked from a “transparency,” or photographic “positive,” instead of a negative. This is the Klick and Fox Talbot method, and is very commonly in use at present.
The process of “photogravure” is well known, as employed by Messrs. Boussod, Valadon, & Co. (Goupil), of Paris, and is adapted for the reproduction of wash drawings, paintings, also drawings where the lines are pale and uncertain, pencil, chalk, etc.; the greys and gradations of pencil being wonderfully interpreted. In London the intaglio processes are used by many of the firms mentioned on page 240. They are now much used for the reproduction of photographic portraits in books, taking place of the copperplate engraving.