Gum Printing, Then & Now

by Christina Z. Anderson

In 1998 I took my first alternative processes class at Montana State University and fell in love with gum printing. It is not surprising it became my process of choice. I came to photography while pursuing a degree in painting, and gum was as painterly a photographic process as there is. I ended up pursuing two degrees concurrently, one in photography and one in painting—I just couldn’t give either area up!

For those readers who don’t know what a gum print is, the term “photographically controlled watercolor” is probably more appropriate. In a way it is not really a photographic process, but a photosensitive process wherein light hardens a layer of gum Arabic mixed with pigment and photosensitive ammonium dichromate in direct proportion to the amount of light received. This means that under the shadow or thinner areas of the negative, a deeper layer of color is hardened, and under the highlight or denser areas of the negative, a shallower layer of color is hardened. With simple water development, the unhardened gum Arabic washes away, leaving a positive facsimile of the negative image. Once dried, this layer is tough, and another layer of pigmented, sensitized gum can be brushed on top and exposed in exactly the same way. Multiple printings can deepen the tonal range of a print, or create a realistic tricolor image. As you can imagine, with each layer requiring its own wet and dry cycle, this translates to a day or two to complete one gum print. However, along the way, there are unlimited possibilities for painterly alteration.

My intentions to do gum exclusively and intensely were delayed 5 years by the ensuing teaching job at MSU, family, and life in general, so it was not until January of 2003 that I returned to gum printing in full force. During those five years, from 1998 to 2003, digital photography took hold and turned our analog world upside-down. For gum printing, this was a good thing and I’ll explain why. Gum printing is a contact printing process, requiring a negative the same size as the resulting image. In 1998 I was either shooting large format 4x5 negatives and making small gum prints, or I was laboriously enlarging these negatives with Kodak Direct Duplicating Film up to 8x10, a film that was taken off the market a while ago. If I wanted larger than 8x10 I had to do a two step negative to positive to negative process on regular sheet film. I had not completed my extensive historical research into the gum process at that time, and therefore I was not aware that many photographers throughout gum’s 160 year history had used paper negatives made from enlarged bromide prints. Now, that would have been much easier.

The historical way to make a tricolor gum print required a laborious amount of analog darkroom work to make enlarged color separation negatives under red, green, and blue filters. Fast forward to today: with a press of a button in Photoshop to “split channels”, instant tricolor separation negatives result. There are few tricolor gum prints from the late 1890’s to the early 1900’s, but chances are, with the simplicity of tricolor negative making today, this is one area that will experience a renaissance.

As far as digital negatives go, in 1998 thanks to Dan Burkholder they were finally getting off the ground. I can still remember the APIS (Alternative Process International Symposium, Santa Fe, New Mexico 1999) meeting where Burkholder passed around the flimsiest pale orange negative I had ever seen—it utilized colorized inks in an Epson printer, which he had discovered held back a lot more light than appearances would have you believe!

At the same time that Burkholder was making his digital negative discoveries, Photoshop was getting better, Epson printers were getting better, and transparency substrates such as Pictorico were created that could hold ink without puddling. All of these factors contributed to a perfect time for a resurgence of alternative contact printing processes.

At my third APIS in 2003 I was fortunate to connect with Sam Wang from Clemson University. There I saw Wang’s tricolor gum prints that blew me away. How could someone get realistic color and smooth skin tones with the gum process? I then attended graduate school at Clemson University to study under Wang. Two years immersion in gum printing plus research through 60,000 microfilm pages of the British Journal of Photography and every book on gum that is in print gave me a solid grounding in the process.

While at Clemson I took a workshop on Precision Digital Negatives, a custom curve system developed and taught by Mark Nelson (see PrecisionDigitalNegatives.com). This was the final piece of the puzzle for my personal understanding of how gum works. Nelson’s system is methodical and specific, and utilized colorized negatives with no black ink in the mix. His system is able to pinpoint which color ink fits which process—for instance, gum bichromate requires a different color negative than platinum. Once such things as standard printing time and color of negative are determined, the development of individual curves is simply a matter of measuring and entering data into the software’s spreadsheet. Suddenly I was able to make observations more grounded in scientific practice. For instance, one finding was that a yellow pigment’s curve looks different than the curves for blue and magenta watercolor pigments. When I thought about it, I realized this shouldn’t be surprising! We use different colors of filters under the enlarger’s tungsten light in the darkroom—from yellow to magenta—to change the contrast of variable contrast papers. Just so, UV light is responsive to color as a filtering mechanism, except that with gum, the colors we use are not only in the digital negative but also in the pigment. When you think about it, in light, yellow is opposite blue, and therefore UV light which is from the bluer end of the spectrum should probably be blocked better by yellow and allowed to pass easier by blue. Throughout history blue has been said to be the fastest exposing pigment, and this makes logical sense. With Nelson’s system, you can quantify this kind of information.


Does gum printing require complexity and curves? No. There are as many ways to gum print as there are practitioners, each promoting his or her own path. I have seen glorious gum prints made from simple negatives printed out on typing paper in a cheap printer. I have also seen my students, who have learned the more complex ways of gum, create a perfect tricolor gum print their first try. If you have gum printed before, and failed, the more methodical ways will ultimately make the process easier and more predictable. One author from the late 1890’s remarked that for some reason, when workers fail at gum, they blame the process and not themselves. Gum has had a bad rap since its very beginnings.

My research has shown me that there is nothing new under the sun in gum printing, and, in fact, there are many old ways of gum printing that have application today. Gum’s heyday was 1894-1920, and then resurrected again in the 1960’s. I have learned most from the turn of the century books. My research will be compiled into a book devoted exclusively to gum printing that is on its way to completion by the end of this year. In the meantime, a 26 page, short version of the gum process to get you started is one chapter of my Alternative Processes Condensed, A Manual of 11 different contact printing processes.

We are hungry for hands-on processes to connect with our work. We get so much of our information through the television and the computer, that is mediated or once removed from our senses. We crave a direct sensual experience with our work today — or, at least, I do. While I am gum printing, I am unaware of time and my surroundings — my focus is so tied into the work at hand. To live in a time where we can combine the best that analog and digital have to offer in hybrid forms of image making is a blessed thing.

Reprinted from MAGNAchrom Magazine, Vol 1, Issue 6. www.magnachrom.com

You can download the entire PDF here:
MAGNAchrom.v.1.6.2.ChristinaAndersen.pdf