The Robert S. and Margaret A. Ames Collection of Illustrated Books
Methods of Printing and Illustration
Woodcut is an ancient medium of illustration, the image being created by cutting away areas of the surface of a block of wood so as to leave lines that receive ink for transfer to paper. Woodcut is a relief process.
Engraving, whether in wood or on a metal (usually copper or, later, steel) plate, is a technique whereby ink is infused into lines that are cut into the base material either by hand or the application of acid. Known as intaglio, engraving is the reverse of the relief technique of woodcut. There are several forms of engraving (e.g. dry point, mezzotint, aquatint, etching) but all employ the same basic production method.
Lithography, in contrast to woodcut or the various engraving techniques, is a surface form of printing whereby an image is drawn in a greasy medium, usually a crayon, upon a stone or metal plate. Once drawn, the image is then etched onto the plate by wiping or brushing the image with a mixture of gum arabic and acid, following which the plate is washed with turpentine which removes the original drawing.
Next, ink and turpentine are rubbed onto the stone, replacing the original crayon; the non-inked areas are protected by the gum in the etch. At this stage the plate is flooded with water to wash off the gum. Then, lithographic ink is applied to the plate by a roller, traditionally of leather, called a brayer. The ink is attracted to the still greasy drawing but is repelled by the water on the bare areas. This process involves placing the treated plate face up on the press and covering it successively by a sheet of dampened paper, blotting paper and a thick sheet of fibreboard called a tympan. The pressure of the press transfers the image from the plate to the paper.
Chromolithography, which produces multi-colored
images, is a very difficult process that employs a separate plate for each color,
with the dampened paper being pressed against each plate progressively to achieve
the desired effect. The tonal capabilities and the ability to use the lithographic
plates for thousands of impressions was the chief advantage provided by lithography
over engraving. The earliest book in the exhibit to be lithographed is John
C. Fremont's Report on expedition to the Rocky Mountains and the west coast,
published in 1845.
Photography had made its appearance in Western exploration accounts well before the "Great Surveys." J. C. Fremont had taken a daguerreotype camera on his first expedition but was unable to operate it and one wood engraving by Nathaniel Orr is noted in Vol. V of the Railroad Surveys as having been taken from a daguerreotype. But these, and a few other examples, were the exception until reliable methods of photoengraving and photolithography became commercially available in the post-war period.
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