If applied to the entire surface, the result is very like a half-tone process block in appearance. This is seen in the illustration on page 85, in which the shading medium has been applied everywhere except in the few white spots.
Such an application is particularly useful for evening or twilight subjects, but it is more usual to employ them locally, especially for skies. They are also largely used by some artists for figures, in the manner shown in illustration on page [65,] in which the shading is so effectively used on the waistcoat and hat of the man.
The pattern of the tint varies greatly, there being more than a dozen distinct designs, a few examples of which are given on page [91].
These shading media are introduced on to the zinc block after printing from the negative (see Chap. [VII.]), for which purpose transparent sheets of gelatine, on which the required pattern has been engraved and previously inked, are used. By pressing these on to the albumen or other surface of the block, an ink impression is transferred, which accordingly protects the surface during etching in the same manner as the rest of the picture. The "shading" need not be restricted to the blank spaces only, but may be pressed on to any part or the whole of the block; and there is no reason why two or more different patterns should not be used in combination on the same subject. The gelatine sheets being transparent, the process worker can see exactly where to apply them, and can do so with considerably intricacy.
SHADING MEDIUM ON PEN SKETCH VIGNETTE.
(Original 5 x 4.)
In sending to the etchers a drawing in which a shading medium is to be introduced, the practice is to mark such portions as are to be shaded by scribbling over with blue pencil; this is at once understood better than written instructions. It had better be stated whether a dark or light tint be required; also whether it is to be vignetted or shaded all over. Vignetting is the most usual, as seen in the accompanying block, page [92.] It is usual for the process people to make a slight additional charge for the introduction of tints; especially if at all complicated. And, of course, if special experiments in the combination of various tints be intended, requiring special care, fair consideration must be made for the additional trouble and labour.