Category Archives: Gum Bichromate

Prep Work

Well, today was spent prepping paper for gum and gum-over-platinum printing. I did two batches of 10 sheets of 11×15 Rives BFK. The first batch had an oxalic acid pre-bath. The last time I used Rives BFK for a platinum/palladium print, I got these funny discolored blotches, which could be attributable to paper pH, so I’m trying the acid pre-bath to see if that makes a difference. Twenty sheets doesn’t sound like a lot, until you realize that I can really only size paper in 10 sheet batches because that’s about all my clothes-drying line in my darkroom can handle. In any case, it’s enough to get me printing for a few weekends, so I won’t have to do it again for a while. It’s a necessary evil in the gum printing process, because without it your gum image would dissolve off the paper in the development step.
Here’s my darkroom sink with ten sheets of sized paper hanging up to dry:

Freshly sized paper, hanging to dry

Sizing is an interesting creature – basically it’s Knox unflavored gelatin with a hardening agent added. To make it, you put a box of four 7 gram packets in 300 cc’s of cold distilled water, let the gelatin bloom for 30 minutes give or take, then mix the bloomed solution with enough water to bring it to 1 liter. Place this new solution in a water bath and heat until the gelatin solution reaches 140 degrees Farenheit. Add your hardener, mix, then you’re ready to coat. I have a bain marie pot that I use on a hotplate for heating the gelatin so it doesn’t scorch, and I can do it in my darkroom instead of on the kitchen sink.

Here’s a shot of my sizing mixing setup-

Sizing prep station

Sizing needs a hardening agent to help it stand up to repeated soakings in water. Hardeners are all something other than pleasant chemicals – typical hardeners are Chrome alum, Glyoxal and Formaldehyde (Formalin), in ascending order of toxicity. This time I decided to give the chrome alum a try because it doesn’t off-gas, has minimal effects from exposure, and requires the least safety gear for handling (latex gloves are sufficient). I had been using Glyoxal before, which requires good ventilation. My darkroom has minimal ventilation, and at this time of year, fresh air comes with a massive temperature penalty. Formalin pretty much HAS to be used outdoors, so that’s not happening either.

Here’s my Chrome Alum, 5% mix-

Chrome Alum

Isn’t it a lovely purple color? Don’t mistake it for grape Kool-Aid though…

New batch of Rives BFK arrived today!

I got a new batch of 100 sheets of Rives BFK from my favorite supplier, Bostick & Sullivan, today. I’ll be having a sizing marathon this weekend getting all that paper ready for gum printing. I’ve not tried a lot of other papers yet, to keep the variables down, but I’ve been quite happy with the Rives BFK so far. It’s a 90# watercolor paper with good wet strength, and I’ve been able to coat up to five layers so far without having to re-size. After I get through this lot, I’ll have to try the Lana Aquarelle I have sitting around. I’m also going to try using an alum-based hardener in the sizing instead of glyoxal because it’s not exactly practical to try and size paper outdoors in this weather, and my basement darkroom doesn’t have good ventilation.

Why I do this stuff

So far this blog has been long on pictures and short on words. Lucky you. I figured it was time to actually write something, and now was as good a time as any to explain how I got into all this giant cameras and funky antique process stuff. The story of it kind of mirrors the story of how I got in to photography to begin with- almost by accident.

I started doing photography after college, as something to do while looking for a job. I originally thought I would learn JUST enough to use it to record subject matter for painting and drawing. It was a means to an end. That plan went out the window when I saw my first negatives come out of the developing tank, and was even more firmly convinced that this was the thing for me when that first print appeared in the red-lit tray on a rack in my bathtub.

Back maybe six or eight years ago, there was this big scare that Ilford might go bankrupt and that silver gelatin paper might go away, and maybe even film too. Well, I was so much in love with wet darkroom printing that I figured it was time to learn how to do hand-coated processes so I could keep using my 4×5 that I liked so much. I didn’t realize what a Pandora’s box this would open. Prior to this epiphany, I was only vaguely conscious of the existence of antique/alternative processes. I knew cyanotypes existed, and someone in a class I took once did some VanDyke Brown prints on fabric. I saw a handful of platinum prints at the View Camera conference, but that was about it.

That event was I think the turning point for me because it was there that I also saw people working in wet plate collidion. My eyes were opened to the possibility of what could be done without commercially manufactured products. After seeing some more prints,
I decided I would try platinum printing. I was mostly shooting 2 1/4 inch square roll film with some 4×5 mixed in at the time, and 4×5 negatives were big enough to learn on, but platinum like almost all other alternative/antique processes is mostly insensitive to non-UV light. This means that you can’t enlarge an image to whatever size print you want from a small negative- you have to work from a negative the size you want the finished print to be.

Realizing the limits of 4×5 prints rather quickly, an 8×10 camera ensued. 8×10 is a beautiful size print but a pain in the ass of a camera. Along came my Argentina trip and a 5×7 joined the family. And so on. Platinum printing became my mainstay as I grew to love the medium for itself, to the point that I have all but retired my enlargers, and only work in contact printed alternative processes. I’ve dabbled in wet plate and I’ve even learned how to make daguerreotypes.

This is my medium, these are my processes, and this is the how and why I make my photos.

More recent gum work

Torso, TC Ong

This image is a simple two-color gum bichromate print. Burnt Sienna and yellow ochre if memory serves correctly. Both layers were manipulated with a watercolor brush to create texture in the background.

Recent Gum Work

Three recent gum bichromate prints. Gum bichromate is perhaps the most labor-intensive photographic process because it involves building an image, one layer of pigment at a time. Most gum images need at least two layers, but often three or four are a minimum. Even working rapidly, you can only do about two layers a day. Gum is one of those processes that is all about the choices you make adding up to a finished product. All three images are whole-plate size images, 6.5 by 8.5 inches. Whole plate is the original photographic format, having been designed by Louis Daguerre for his first camera. Whole plate has a long and varied history, having come in and out of fashion repeatedly. It is enjoying a small modern-day renaissance not only for its historical echoes but for its aesthetically pleasing proportions and relative size.

This first image is a gum over Ziatype. Ziatype is a printing-out version of Palladium. A printing out process is one where the image is fully formed during exposure, and does not need a chemical developer to produce a final image. Ziatypes are really neat because they offer a very wide range of contrast, color and tonality depending on how you mix the chemistry. I do the Ziatype under the gum to start with a sharp base image with well-defined shadows and midtones.  The gum builds on top to add physical texture and create color.

The second image is a pure gum image, with only two layers, black and blue. As you can see, it is possible to create a successful gum image with only two layers of pigment. I manipulated the layers to bring out the blue color and the detail in the hair.

The final image is a four layer gum bichromate. It is a pretty accurate representation of the model’s actual skin color, but it is made from a single black-and-white negative. I worked it over with a watercolor brush during the printing process to bring out the highlights on the model’s back.