Page 16 - PCMI Journal July 2018

David Allen | Emeritus Professor | Cranfield University | UK Photochemical Machining: Where has it come from, and where is it going?
The spread of knowledge is often tightly controlled for political purposes and whilst illuminated manuscripts hand-written by monks were an excellent source of knowledge such manuscripts were unique and took a very long time to produce.
Woodblock printing has been used as a faster method to produce illustrated books since 200 AD. Its main principles include carving into a wooden block to create recesses, the spreading of ink onto the flat (uncarved) wooden surface and transferring the ink onto paper by the application of pressure (letterpress).
The next major development was to use metal as the ink transfer medium instead of wood. The Gutenberg Bible was the first major book printed using mass-produced movable metal type in Europe. Written in Latin, the Catholic Gutenberg Bible is an edition of the Vulgate, and was printed by Johannes Gutenberg, in Mainz, in present-day Germany, in the 1450s.
The nineteenth century saw the beginnings of photography as we know it today and with it came the development of a new type of photosensitive resist known as photoresist. J.N. Niépce has been credited with the first photoetching, having succeeded in 1826 in etching pewter (an alloy of tin and lead) through a photoresist stencil formed from bitumen of Judea asphalt that had been developed in a mixture of lavender oil and mineral spirit [Hepher]. Niépce’s pewter plate was the source of the first photograph from nature, made in a camera obscura with an eight-hour exposure to sunlight! Niépce experimented further by reproducing an engraving by Isaac Briot (1585-1670) as shown in Figure 1.
Figure 1. (Left) Engraving of Cardinal d’Amboise (Right) Photoetched plate of the engraving made in 1826 or 1827.
Issue 131 July 2018 PCMI Journal 15