The Gum Bichromate Process

13 The Gum Bichromate Process OVERVIEW AND EXPECTATIONS At first glance, the gum bichromate process looks amazingly uncomplicated. However, to nearly every one of my students who has been seduced by the process, and for those artists who are dedicated to it, gum is one of the most complex in the alternative genre. Gum bichromate printing is certainly seductive due to its limited chemistry, simple water development, and unlimited color potential with watercolors of the artist’s choice. Gum printing is quite flexible and easily combined with other processes and graphic disciplines. Because of its pigment, paper, and brush roots, gum bichromate is one of the few photographic processes capable of achieving that wonderful element of gesture—gesture being that painterly expression of the “artist’s hand” in the creation of a mark. In this chapter I, as always, give you a little history and describe how the process works. I then discuss the negative and a technique, euphemistically referred to as registration, that will allow you to place multiple applications of color on the same piece of paper without losing the original sharpness of the image. You will also learn how to make a gum print from a single contact negative. You’ll learn about mixing the chemicals for the sensitizer and the relationship among the three primary ingredients in the technique: gum arabic, a dichromate sensitizer, and watercolor pigment. This is followed by instructions for applying the coating, processing, and the reapplication of the sensitized coatings. A discusion about development and clearing gum prints is included, and the chapter concludes with a comprehensive trouble-shooting section. 220 Figure 13–1 Christopher James, Grace in Gum, 1977 This is from a series of gum bichromate portraits that I made from damaged internegatives that had been thrown in the trash in the Harvard photography labs. The final negative was enlarged on SO- 339 direct duplicating film (now SO-132) and then abused for several days with gum bichromate applications, paint, ink, dyes, bleaches, and etch- ing tool abrasion in wet emulsion. (Courtesy of the author) 221 Figure 13–2 Robert Demachy (1859–1937), Cigarette Girl (Gum bichromate print reproduced as a photogravure in Camera Notes, Vol. 6, No. 1, July 1902) Robert Demachy was an artistic force in the 1880s and began to interpret his work in gum in 1894, because it allowed him to use consider- able handwork and was similar to the feelings he had when looking at Impressionist paintings. Demachy founded the Photo-Club de Paris and was a stalwart member of the Linked Ring as well as an honorary member of the Royal Photographic Society. In spite of his success, Demachy completely divorced himself from photography in 1914. T H (Courtesy of the George Eastman House, Rochester, E B NY) O O K O F Considering the surface simplicity of the process, you’ll sionate and stubborn of all alternative process artists when A L T notice that there is a lot of information to absorb, and I it comes to their particular way of doing the process. I can E R N want you to see that the variables within gum printing are just imagine many of my friends reading that last sentence A T I infinite. If you investigate the process beyond this book and saying, “He’s talking about me!” V E you will find published evidence that will occasionally You’ll find that you’ll be able to make excellent gum P H O seem contrary to portions of the information in this chap- prints using, and adapting, the instructions in this chap- T O ter. Some of that information will work quite well for you, ter. Just relax, keep notes of what you are doing, and real- G R A whereas morsels of other instruction will not work for you ize that the gum process will reward you if you work at it P H with equal success. In gum printing there are very few without a need for instant gratification. Have a great time I C P absolutely correct ways to do anything, and much of what individually modifying the myriad elements of the tech- R O C has been previously published has simply been the proce- nique to suit your own personal working style, imagery, E S S dure of choice for the individual teacher or author. In my and intentions. E S experience, gum bichromate printers are the most pas- 222 Collotype: Calotype The Collotype is a photomechanical/lithographic-like process invented by Alphonse Louis Poitevin (1855) in which a pane of ground glass is coated with a bichromated gelatin. The coated glass is next baked to create a fine reticulated (grainy-mezzotint-like) surface. The baked glass is next exposed to a negative under UV light, and the bichromated gelatin hardens in proportion to the exposure, as in a gum bichromate print. The plate is then washed, so that the unexposed/unhardened gelatin washes out, and then coated with glycerin. The glycerin coating allows the remaining bichromate to be hygroscopic (able to absorb moisture from the air) in proportion to the degree of the bichromate’s exposure. To make a print, the plate is rolled with greasy lithogra- pher’s ink; the ink adheres to the exposed areas of the plate with the least water content, and then printed on paper. Commercial usage was common following the perfection of the process by Joseph Albert in 1868. The Calotype, invented by William Henry Fox Talbot in 1835, is the name for the first photographic process to Figure 13–3 produce a negative that would facilitate the making of a Cover of Issue # 3, The Pencil of Nature, 1844 direct positive. In the Calotype process a piece of high- (Courtesy of the Royal Photographic Society) quality writing paper is sensitized with a solution of silver iodide: potassium iodide and silver nitrate. Prior to exposure, a second solution of silver nitrate, acetic acid, A LITTLE HISTORY and gallic acid is applied to the paper (increasing the An interesting hypothesis from a book by Picknett and light-sensitivity), dried, and exposed to UV light. The Prince entitled, Turin Shroud—In Whose Image? The Truth exposed image is then resensitized with a solution of Behind the Centuries-Long Conspiracy of Silence (Acacia gallo nitrate of silver (gallic acid and silver nitrate) that Press, 1994) suggests that Leonardo da Vinci (1452– causes the latent image to emerge. The print is then 1519) may have been the creator of the Shroud of Turin S S E fixed in a solution of potassium bromide or sodium chlo- by using a mixture of dichromated egg with human or ani- C O ride, and after it has dried, used as a negative (some- R mal urine. Guess whose image is on the Turin shroud? — P E times waxed, or oiled, to enhance the transparency of why, it’s da Vinci’s self-portrait, of course. The book’s T A the paper negative) in contact with a newly sensitized authors, if correct, would give Leonardo da Vinci credit M O piece of paper to produce a direct positive. This process, R for the first photographic image several hundred years H C I following some improvements, was renamed the Talbo- before the medium’s “official” beginning. To put this curi- B type and is, in current definition, much like a salted paper M ous factoid in context, the publisher’s catalogue is rife with U G print. In 1844, Talbot published the second photograph- books dealing with conspiracy theories dating back to the E H ically illustrated book, The Pencil of Nature, hand tipping fourteenth century. Who knows? Considering everything T 3 his Calotypes throughout the manuscript. else da Vinci accomplished, it might be true. 1 R E T P A H C 223 when he discovered that paper impregnated with potassium bichromate was sensitive to light. Ponton modestly christened his discovery the Pontontype. In Ponton’s process, paper was coated with a potassium dichromate solution and exposed to sunlight using objects to create a negative image. The exposed print was then washed, to remove any unexposed dichromate, and dried, leaving a sepia brown positive image that consisted of chromium dioxide. The print was rather handsome at first but tended to fade to a gossamer-like green after several months. Ponton’s single solution Pontontype is directly related to the idea behind Poitevin’s Dusting-On process (1858) and a sizing technique for liquid emulsions on paper, both of which are covered later in this text. A year later, in 1840, Edmund Becquerel (1820–1891) added to this rapidly expanding base of knowledge by producing images using starch in combination with iodine. It was Becquerel, by the way, who first figured out that Daguerreotypes could be supplementally intensified by the continuation of the Daguerreotype’s exposure through a red glass filter. In 1854, William Henry Fox Talbot began working on the concept by observing the ability of potassium dichromate to have a hardening effect on a colloidal gel- Figure 13–4 atin that was directly proportional to the degree of UV Antoine Francois Jean Claudet (1797–1867), Woman, 1844 light that the gelatin received. Fox Talbot’s modest success (Salted paper print from a Calotype negative) Claudet learned the Calotype process from Talbot but bemoaned the fact in this area was followed by the work of Alphonse Louis that it was too slow and less perfect than the Daguerreotype that he had Poitevin (1819–1882), who continued the investigation learned from Daguerre.

Load more