. Bulletin - United States National Museum. Science. Wkii'.'â \' --^ *' â N 1 rS ":. Figure 17.âSiderography specimen piati:. 1819. Reduced from 8x6 inches. (Original in Constance Meade Collection, Oxford University Pi'ess.) by the old case-hardening method. Next a small cylinder of mild steel was rolled and pressed re- peatedly over the engraving, by means of a special machine, forcing the softer metal into the engraving until the image was transferred in raised lines to the cylinder surface. The cylinder was then hardened and used in its turn to impress the image into any number of mild
. Bulletin - United States National Museum. Science. Wkii'.'â \' --^ *' â N 1 rS ":. Figure 17.âSiderography specimen piati:. 1819. Reduced from 8x6 inches. (Original in Constance Meade Collection, Oxford University Pi'ess.) by the old case-hardening method. Next a small cylinder of mild steel was rolled and pressed re- peatedly over the engraving, by means of a special machine, forcing the softer metal into the engraving until the image was transferred in raised lines to the cylinder surface. The cylinder was then hardened and used in its turn to impress the image into any number of mild steel plates, this time once again in sunken lines. These plates were then hardened for printing. Thus a single engi-aving, however complex, could be copied exactly on to any number of plates. or the engraving could be repeated several times on the same plate. The blacks and whites of an image could be reversed by a change in the order of trans- ferring: if an extra cylinder was introduced, or if the initial engraving was made on a cylinder rather than on the flat plate then the final printing plate would hold the image in raised rather than sunken lines, and the printed result would be a white line design on a black ground. The siderography process had enormous advantages for bank-note printing. Since the plates were copied PAPER 71: SIR WILLIAM CONGREVE AND HIS COMPOUND-PLATE PRINTING 81. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States National Museum; Smithsonian Institution; United States. Dept. of the Interior. Washington : Smithsonian Institution Press, [etc. ]; for sale by the Supt. of Docs. , U. S. Govt Print. Off.
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Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
