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Alternative Photographic Processes - (Hand made photographic -emulsions and processes)

Processes - Photogravure 1879 -

Discovery Photogravure is a photomechanical process. i.e. the prints are made using a printing press. It can produce high quality prints in large quantities. The process is derived from Talbot's photoglyphic engraving, but was not invented until much later. It was invented in 1879 by the Austrian printer, Karel Klic (1841-1926). Karl Klic went on to develop screen gravure (retrogravure), a process that was widely used for newspaper printing until the 1910s. Process Photogravure consists of etching an image on a copper plate, previously-prepared with a grained surface, so that the etched area can hold printing ink. Description of the process 1. Prepare a copper plate by cleaning with a weak acid then with potash. 2. Lay a ground upon the copper plate. The ground is made by up of fine dust and bitumen. Warm the plate gently until the bitumen adheres to it. 3. Use the original negative to make a carbon positive on a transparency, and allow to dry. 4. From the carbon transparency make a carbon negative onto, say, Autotype tissue. This is called a resist because it will, at a later stage, resist the action of the etching fluid. 5. Lay the resist on the grained copper plate and develop (as for a carbon print) with warm water. Then dry the resist, using alcohol to do so. This will leave a coating of gelatin on the ground copper surface, thinnest in the shadow. 6. Etch the copper plate through the resist. Do this by placing in a dish containing perchloride of iron. 7. Wash the resist off the copper plate, then print from the plate. The printing is normally performed by a professional copper plate printer. I believe that the notes above were taken from a book published in the late 19th century. Below is a rather different description based on an account in Looking at Photographs by Gordon Baldwin Alternative description of the process Proceed as above, except replace steps 3, 4, 5, 6 by: 3a. Use a negative of the picture to be reproduced to create a transparent positive 4a. Coat a tissue on one side with gelatin sensitised with potassium dichromate, then expose it to light under the transparent positive. The gelatin will harden more on those parts receiving the greatest amount of light. 5a. When wet, firmly press this tissue, gelatin side down, onto the prepared copper plate, then peel away the backing in warm water. 6a. Place the plate in an acid bath, where the parts with the least covering of gelatin will be etched more deeply. 1893 Lecture The process above was described at a lecture given to the Photographic Society of Great Britain in 1893. The journal Photography, commenting on the lecturer, Mr Dennison, reported: "... the Society, and photographers generally, have been in luck's way to secure so capital an exposition and so lucid a lecturer upon an almost unknown process." [Photography: 2 Mar 1893] Result The photogravure process is generally highly regarded, being able to produce high quality copies, with the images with charcoal blacks and bright whites, embedded in the fibres of the paper. Results using rich sepia ink can also be very attractive. Photogravure images have been described as having the subtlety of a photograph and the art quality of a lithograph. [Appalachian Arts web site] The finished picture shows the mark of the plate around the picture. The process can produce



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