Gum Bichromate Photography
Gum Bichromate photography is another form of alternative photography similar to Van Dyke and Cyanotype, only much more involved. After working with Cyanotype and Van Dyke prints in lab, we decided that we wanted to try other types of alternative photography and Dr. Bordley suggested trying Gum Bichromate. This process was discovered in 1839 and is similar to carbon printing. Some good sources for information on this are past project work and journals that specialize in alternative photography.
Our purpose in this experiment is to produce a high quality print using Gum Bichromate photography. We intended to reproduce the experiment of Autumn Borchak, but use different variables such as: types of paper, concentrations of gum Arabic, exposure times, amounts of sizing and hardening solutions, amounts of pigment, and internal and external sizing.
Paper. Handmade paper from hardwood pulp with internal sizing. Also used Cyanotype and embossing paper.
Pigment: Grumbacher watercolor in Gum Arabic 14 degrees baume
Knox food gelatin
Bicarbonate of Soda
Formalin: 3% solution
Negative with glass frame like Cyanotype
Tray for developing
UV light source
Preshrink paper. Use a large pot that can be put on a hot plate and fill with hot water, use hot plate to keep hot. Place each sheet of paper in water and turn once to check for airbells. Allow water to sit for 15 minutes then remove and hang to dry.
Sizing the paper: Fill pot with water and sprinkle gelatin over water and stir gently until gelatin is all wet. Allow to sit for 15 minutes then place paper one sheet at a time in water, turning each sheet once to check for airbells which you brush off. After ten minutes, flip stack and remove from pot, the first piece in is the first piece out. Lightly wipe with fingers to aid in drying before hanging to dry. This step must be done twice. Save yourself two weeks of work and do it twice the first time! Size then hardening bath, size and then hardening bath again!!
Glyoxal hardening bath: Fill pot with about a liter of water, more if you have a large amount of paper. This can either be made with a 1% solution of glyoxal or a 3% solution of formalin. Use 15 to 25 ml of formalin per liter of solution. Add 10 ml of methyl alcohol per liter of solution and 1/2 teaspoon of bicarbonate of soda per solution (baking soda). The formalin is toxic so remember to wear gloves and goggles. Place paper in one sheet at a time and allow to sit for 7-10 minutes, flip stack over and remove, the first one in is the first one out. Gently wipe solution off with fingers to aid in drying. Hang to dry. Note: this solution can be reused for second hardening bath. Do not pour this down the drain. Between used, store in glass jar and cap lid tightly. This step is very important to making the experiment work. If this step is not done correctly with the sizing, you will not get any results.
Sensitizer: This solution is prepared from a mixture of 13% solution of potassium dichromate in a 1:7 ratio with distilled water. Suggested starting point is 100ml of total solution. The potassium dichromate is also toxic so glove and goggle use are necessary. This solution must be mixed with the gum Arabic solution.
Gum Arabic: Use a 1:2 ratio of gum Arabic with distilled water, suggested starting point is around 100ml for total solution. Heat the gum Arabic mixture on the hot plate in a glass beaker for 30 minutes. Be sure to keep the hot plate at a very low setting, this will boil and spill over very easily. After 30 minutes, the mixture must sit for 10 minutes before it can be used. Add pigment after 10 minutes, about 1ml of pigment per 100 ml of solution. This can be measured by dropping pigment into beaker until the solution rises 1ml. Then the gum Arabic and potassium dichromate mixture must be mixed in a 1:1 mixture. If you are using more than one pigment, first divide the gum Arabic solution into separate beakers in equal amounts for each color adding the pigment and then the potassium dichromate.
Exposing: Using a paint brush, lightly brush the pigment onto the dried paper first horizontally and then vertically making sure to cover fully. This must be done in a room with a safe light so as not to expose the paper prematurely. After allowing paper to dry, about 10 minutes, place paper in negative and expose to UV light source. If exposing in sun, exposure time will be 1-3 minutes. If exposing in UV light box, exposure time will be 5-7 minutes.
Developing: After exposure, place in tray of room temperature water to soak, face down. Unexposed gum Arabic will wash away after 6 minutes and full development will take about 30 minutes. Note: If an image is appearing when you expose and disappears after developing, you probably do not have enough sizing in your paper. Make sure you size and harder each sheet twice before starting exposure. Hang to dry.
On our first attempt at this project we only sized and hardened the paper once, although some of our handmade paper had internal sizing. After exposing our paper in the UV light box, some of our paper had prints on them, while others did not. However, after developing, all the prints washed away. After the fist experiment we had no clear image. We suspected that our problem was either with the gum Arabic solution or the sizing of the paper. Therefore we changed the gum Arabic mixture from a 1:3 mixture to a 1:2 mixture hoping that an image would form and repeated the exposure and development process.
This did not produce a clear image, although the paper was stained by the pigment, so we determined that the gum Arabic was not the problem. Dr. Bordley suggested that we size and harden the paper twice before using because it was possible that the pigmented solution was soaking into the paper.
For our second attempt we sized and hardened the paper twice before applying the gum Arabic solution. We used the same 1:2 mixture and again tried to expose in the UV light box without success. We determined that the sizing was not the problem either. Since these two attempts were not successful, we decided to try experimenting on our own. We changed the experiment by not preshrinking, sizing, or hardening the paper. We also did not heat the gum Arabic or add any pigment to the paper. Surprisingly, this produced the only prints that we were able to create and all of the unexposed gum Arabic washed away. Once we determined that this would produce an image, we varied the exposure time and exposed the paper in the sun.
We determined that the pigment that we used was not a high enough quality to be used in this experiment and therefore when we eliminated the pigment, we produced a print. Generally any type of pigment sold in the bookstore is not a high enough quality. Some suggestions for continuing this experiment are to use thick paper (the thinner paper tore after multiple washings). The optimum exposure time for these prints is between 3 and 5 minutes. This produces a high quality print that is both dark and detailed. This experiment requires large amounts of time for unforseeable problems.
Original Plan versus Final Experiment:
In our original plan, there were many complicated steps that were required to obtain a print. However, in our final experiment, we discovered that these steps were not necessary to make a nice print. Our final results were colored from the pigment, rather they were colored from the gum Arabic and potassium dichromate mixture. We maintained our original purpose by varying several elements of the experiment, however it clearly became our objective to achieve one clear Gum Bichromate print. Although this experiment is extremely interesting, we suggest that you do not begin experimenting without ample time to finish.
We would like to thank Dr. Bordley for his assistance, guidance, and understanding concerning our experiment. We would also like to acknowledge that we were using the project of former student Autumn Borchak in procedure and history for our experiment. In addition, we are grateful to Emily Weingrovius for allowing us the use of her pulp. Also, many thanks to Kate Rambo and Jerry Whitaker for their patience and experienced advice in our struggles in the lab.
Meghan Rogg and Carrie Thompson