A polished copper plate is grained by dusting resin or asphalt powder on its surface, and afterwards fixing it by the application of heat. A tissue negative print is made, squeezed on to the grained plate, and developed in the usual way. The plate is etched through the tissue. The action of the etching mordant—perchloride of iron—being in exact proportion to the light and shade of the developed print.
The printing is a necessarily slow, and therefore costly, item. This limitation to their production, however, enhances the value of photogravure prints.
Ink Photo.—What is known as the ink photo process of reproduction is interesting chiefly on account of the remarkable fidelity with which engravings of the finest and most intricate texture can be reproduced by its agency. It is essentially a photo-mechanical process, but differs from others of a similar character, inasmuch as the vigour and expressive power of the original is to a considerable extent preserved. Colour values also, as far as they can be expressed by the engraver's art (see p. 11), are reproduced by ink photo methods with surprising accuracy, and the intensity of impression, that peculiar feature of prints from engraved plates, is almost invariably well sustained. A careful criticism of the appended illustration and frontispiece done, this process will reveal many other interesting points of practical value.
CHAPTER VIII
APPRECIATIVE CRITICISM—AN EDUCATIVE PRINCIPLE—AN ANALYSIS—REALISM IN ART—A RETROSPECT