Читать книгу Prints. A Brief Review of Their Technique and History онлайн

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We have now reviewed the relief processes, both dependent entirely on hand work, and the intaglio processes, engraving, dry-point, mezzotint, likewise relying upon manual power to prepare the plate for printing. In the etching group of intaglio devices, a chemical factor is called upon to lessen and accelerate the work of the hand. The last group to be considered, planographic processes, is based entirely upon chemical and physical action. The drawing to be reproduced is made with fatty crayon or ink upon a slab of a special variety of limestone; the stone is then treated with acidulated water, and with gummed water. As a result, when the stone is moistened, all those parts which have been drawn upon reject the water, but have an affinity for printing-ink, while the portions not drawn upon have an affinity for water and reject printing-ink, as long as they are kept moist. Neither by ridges nor sunken furrows, just from one plane surface,—hence the term “planographic,”—merely by the enmity of water and fatty ink are these lithographic impressions obtained. Plates of metal are often substituted for stone (zincography, algraphy), but the process always remains the same.