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51.3 MB (51.0 MB compressed)
5319 x 3369 pixels
45.0 x 28.4 cm ⏐ 17.7 x 11.2 in (300dpi)
SHEILA TERRY / SCIENCE PHOTO LIBRARY SHEILA TERRY / SCIENCE PHOTO LIBRARY
The need to make thousands of prints for mass publications from engraved woodblocks was achieved in the nineteenth century by a process of electrotyping. Here, gutta percha (latex) moulds are made of the engraved woodblocks and after coating with blacklead (graphite), they are suspended in a tank filled with blue vitriol (copper sulphate solution). The moulds are connected to the positive pole of a galvanic or electric battery, the negative pole to a copper plate. A film of copper is deposited on the graphited surface of the moulds, and, after a certain time in the bath, reaches the required thickness. This layer is removed from the mould, reinforced with type metal and suitably mounted so as to withstand the enormous pressures of the printing presses.
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