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Tri-Color Gum with Cyanotype
My tri-color gum process may be different from others’ in three areas: 1/ Digitally created color-separation negatives, These contribute to the success of my prints, as well as to their distinctive “look.” This look may not be suitable for anyone else. What follows are some details that more seasoned alt-process
printers may find useful, but are by no means a fail-proof step by step guide.
First, a couple words on my imagery: from way back I’ve been interested in intermixing scenes from different times and places to suggest something beyond the surfaces and the obvious. I leave the simple straightforward and confrontational approaches to the traditional silver prints that I continue to make. With digital images, I can freely manipulate and use subjective colors, colors that don’t have to be perfect or correct. A great variety of methods are on hand to connect and interlace images in the digital arena, much superior to physically cutting and taping pieces of Kodalith films together as I once did for photo-silkscreen. Other than that, I do not hold any central theme or philosophy with my imagery, except that there be a hint of ties to photographic reality and that each is a new vehicle for discovery.
DIGITAL COLOR SEPARATION NEGATIVES When I’m satisfied with an image on the computer screen, I take the following Photoshop steps to color-separate it into 3 separate full size greyscale negatives: The density range I usually aim for is about log 1.0. However, one of my “more successful” prints, one of a dead bird, was made from negatives printed in color inks on an HP printer with a much higher density range. So when I say, “I don’t know” in answer to the question, “What’s the negative density range for gum or cyanotype?” I’m not putting anyone on. It appears that anytime I felt I found some sure way to do one thing, something else would happen to remind me that I don’t know it all. I encountered many difficulties when I first began making gum prints: it was not clear which paper to use; my exposing light (a sun lamp) was highly inadequate; plus a myriad of other problems. I was also using panchromatic film, making “in-camera” separations, holding RGB filters in front of the camera lens for three exposures onto 3 separate pieces of black and white film. I also made color separation negatives from color transparencies by enlarging in the darkroom. Both of these methods were not only tedious but often produced negatives very difficult to print - densities and contrasts that were hard to control and working in the dark with panchromatic film was definitely not fun. The fact that I got a few halfway decent prints is something of a small miracle, and represents hundreds of hours of frustrating work! Digital negatives by comparison greatly simplify the process. Nowadays I use color images from digital cameras as well as scans from slides, and the negatives print much more predictably. CYANOTYPE
Many well-sized papers work well with gum printing. For many years I used Rives Heavyweight, a nice paper but also very soft – it abrades easily and with more than a couple layers of gum you begin to get a grainy effect. Some folks may find this grainy look desirable but not me. Watercolor papers seem to do better. Paper choice also affects the cyan layer a lot, as each paper will give a different blue, bluish green, or royal blue after a layer of gum is laid on it. The paper is not additionally sized (watercolor papers are already well-sized) but soaked in hot water for about an hour to pre-shrink, and allowed to dry thoroughly before use. Watercolor papers I have found to work well include Fabriano UNO and Fabriano 50. I use the traditional cyanotype formula (“classic” solution A: 50 g ferric ammonium citrate to 250 cc water; solution B: 25 g potassium ferricyanide to 250 cc water). To print the cyan layer with the “C” negative, the one from the Red channel, I use 2 parts A with 1 part B of the stock solutions for increased printing speed. I also add a little vinegar to the first wash, or soak, to further increase speed and to smooth out the highlight tonality. A word of caution: the addition of vinegar to the wash water will also cause some of the blue to float and it will reattach to the tray and everything else. To minimize the problem, use a fresh bath of vinegar with water for each print. In addition, the print needs to be immersed in it in one smooth motion or edge lines could form. The cyan layer is “developed” for only as long as it is necessary to be free of the yellow unexposed emulsion. In most cases this takes no more than a couple of minutes.
GUM I prefer to mix my own gum by dissolving gum-arabic powder or granules in water, at 1 part gum to 2 parts water. After it’s all dissolved I add a few drops of 100% thymol (10 grams thymol in 10 cc of
isopropyl alcohol) to preserve the solution. I find this gum to “develop” cleanly and in less time than the graphic arts product often called Gum-14, which can vary a lot from batch to batch and often
contains too much preservative to develop (re-dissolve) quickly.
EXPOSURE When dry, the print is placed emulsion to emulsion in contact with the “Y” negative on a light table, registered by eye, and affixed with short lengths of removable tape. Place the combination in a contact printing frame or the vacuum bed of a “plate burner” and expose for an appropriate time under UV lights - using test strips to determine proper amount of exposure. DEVELOPMENT Place the exposed print in a tray of slightly warm water - about 85 º F - for a minute or two. Then transfer to a second tray filled with room temperature water (70 to 80 º F). Leave it floating faced down for about 5 to 10 minutes, then check to see how it’s developing. There is a lot of leeway at this point - unless the print is grossly over or under-exposed, development is usually complete in about 10 minutes. When development is judged to be complete I give the print a quick rinse in cold water and hang it up to dry. At this point a minute amount of pigment will still run off the image, which I generally do not try to prevent since it is part of the process. If that were not acceptable, I would give it more exposure and longer development.
RED (MAGENTA) GUM
HOW I GOT STARTED It was Phil Davis who first suggested combining cyanotype with gum. Apparently records of this kind of this combination can be traced back to the early years of the 20th century though I have never seen any of the prints - actually I have hardly ever seen any historical tri-color gum. After my initial experience of using cyanotype with gum sometime around 1990, the advantages were so obvious that I have been using this combination ever since. Phil also convinced me to mix my own gum, and introduced me to the concept of 2-color separation. Additionally, I learned BTZS system (Beyond The Zone System) from Phil, and this made me understand the whole business of sensitometry, the relationships between exposure, development, density, and contrast--a tremendous shot in the arm for both my silver work as well as the alt processes. (And it was Phil who introduced me to Franklin Enos, who did so much before his death in the mid-Eighties in getting me started with casein and gum, and Sandy King with carbon.) WHAT ELSE DO I DO DIFFERENTLY & WHY For single-coat processes I have never found it necessary to size the paper beforehand. At one time I did size papers for printing tri-color gum and tri-color casein but the process of sizing and hardening can be both messy and time consuming! One of the beautiful things about using cyanotype in tri-color gum is that the paper needs no additional sizing. (Did I hear a chorus of “Hallelujah”?) I always wondered why people do things that are not really necessary just because some “authority” told them to do so. I usually prefer stumbling along on my own instead of doing a lot of reading or research on others’ working methods. Only after some experience would I compare my experience with those from others. My methods consequently may be very different from those of the “gurus” but they have worked fine for me. And to me, the goal in making gum prints, or anything else, is absolutely not to just produce great- looking prints. The prints are but by-products of our search for technical and aesthetic answers, and not ends in themselves. If I were able to spell out the exact foolproof methods of making tricolor gum prints, what would be left? Cibachrome (Ilfochrome) is bright, colorful and permanent, and not hard to do at all in a closet darkroom, and it comes as a kit with foolproof instructions. But can anyone imagine making Cibachrome prints and showing them off at APIS? There is just no one-size-fits-all way to make gum prints. I believe that the variables are too numerous for anyone to lay out a failsafe method. In fact, I’m convinced that I have just scratched the surface in terms of the potentials of this medium. Not infrequently as I go through my reject piles wondering which ones I ought to discard, the prints I rejected earlier because of some perceived technical flaws may present themselves on second consideration as beautiful, fresh, and worth keeping! What that means is that great technical command is not easy, nor absolutely necessary to make good images. Having fun doing it is crucial: “fun” in this sense is synonymous to the exhilaration of being able to ride the bicycle for the first time without falling – WOW, I’ve gained new ability and new insight! I’m addicted!
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3. Split Channels - separating the RGB file into 3 distinct grayscale documents.
6. Print on the proper transparency material. Using black ink only, I usually
print on the readily available (and cheaper) overhead transparency material for inkjet instead of the premium quality variety from Pictorico. Printing on
Pictorico OHP with color inks obviously would also work and may alleviate some problems such as banding that sometimes occur.
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Text and images copyright 2003 by Sam Wang. All rights reserved. |
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