The act of engraving text and image onto materials for commonfolk to read has dated back to 750CE. The first engraved printing units were wood engravings, such were seen in the Chinese Diamond Sutra that was created in the year 868.
After these wooden engravings gained popularity, people started to make printing units out of metal plates using different types of metal – specifically copper and pewter. These metal plates were made able to print by a process in which an image in wax or bitumen was drawn on, or transferred to, the surface of the plate and nonimage areas removed by action of appropriate acids.
Photoengraving was only invented in 1813 by researcher Joseph Nicephore Niepce. He coated a pewter or copper plate with a photosensitive asphaltum and exposed the surface to bright sunlight through an etching of a portrait, which served as a positive image. Sunlight passing through the background of the etching hardened the asphaltum, while the protected areas, under the inked portion of the etching, were developed in oil of lavender and white petroleum to create an image in exposed metal. This image was then etched into the plate, and from the intaglio image, prints were made on a copperplate press.
Example of photoengraving on wood
In 1851, wet-collodion process for photography was introduced, and it provided a means for producing a photographic negative as the basic element in the preparation of engravings. This photographic process also provided a method of stripping the photographic image from the glass plate, permitting assembly of a number of images for plate making, and also making possible the geometric reversal of the image needed in letterpress plate making to produce a right-reading print on paper.
Soon after, the halftone process allowed people to produce shades of grey, in which the image is broken up into dots, and variations of gray tones are obtained by varying the size of the dots, thus controlling the amount of ink laid down in a given area.
The discovery of the halftone screen was primarily responsible for the development and growth of photoengraving; further growth was related to other developments in the printing and allied industries. The introduction in 1935 of the first practical colour film for amateur and professional use probably did more to accelerate printing developments than any single invention. By making bulky studio-type colour cameras obsolete and permitting the use of readily portable camera equipment for the production of colour images, on-the-spot colour photography became possible, greatly increasing the use of coloured illustrations.
At approximately the same time, the commercial production of coated paper and heat-drying printing inks for letterpress printing began. Many colour developments for films, printing processes, and materials followed.
Now in our current society, photoengraving is used for specialty printing, such as foil stamping, embossing on paper, wood and cork branding for the wine industry and chocolate coin engraving and molding plates. It is also used by designers to simulate various products for photography shoots and right reading plaques for casting in bronze.
R E F E R E N C E S
http://www.bauerengraving.com/
https://www.britannica.com/technology/photoengraving/Modern-photoengraving-techniques
