First Successful? 3 color gum print

Getting there.

It is certainly satisfying.

Cyanotype and VDB over pigment

These prints are made by layering cyanotype or Van Dyke brown over an pigmented inkjet print.

The images are first blurred and then printed light (high key) on watercolor paper.

A full sized negative is created and printed onto an overhead projector sheet.

The emulsion is applied, dried and then exposed.

Development is as normal for cyanotype and VDB prints.

Cyanotype over pigment

Van Dyke Brown over pigment

Summer of Alternative Photography

Van Dyke Brown Print

• Selenium toned

Gum Print

• Multicolored gum

Gum Oil Print

Carbon Print

Cyanotype Print

• Coffee toned
• Tea toned 
• Tannic Acid toned
• Cyanotype on glass

Lumen Print

Chemigram

Anthotype

Gum Printing - Operation

Anyone who played the Milton Bradley game "Operation" when they were younger knows the feeling. You take a deep breath, get you fingers just right on the tweezers, pick a piece that you want to try to take out, slowly, very slowly, you work the tweezers into the space. You are almost there. You squeeze the tweezers together and pick up the funny bone, then you start to raise it out of the body. BZZZZZ!!!

Damn!

Gum printing is similar. But much much worse.

This morning I had the following experience.

I spent time going through my photos to choose one I wanted to print.

I made converted it to a negative in Lightroom, carefully adjusting the shadows and highlights to print well (or not). I added a halftone screen in Photoshop to encourage smother tonal transitions.

I fed the Pictorico OHP transparency film into the printer and set the drying time per pass to 30 milliseconds.

Slowly, but surely, the negative emerged from the printer.

I registered the negative onto the watercolor paper by marking the corners of the image with an imperceptibly small dot.

Earlier, I had prepared the gum emulsion for coating the paper. 12ml of gum arabic was drawn up into a syringe and put into a small metal mixing bowl (which was prepared by mixing 30g of powdered gum arabic with 100ml of water and stirring, stirring, chilling, stirring, waiting, stirring, etc). 9g of lamp black was carefully weighed and then mixed into the gum. Mixing, mixing, mixing. Then, donning rubber gloves, another syringe draw 12ml of poison, I mean Potassium Dichromate from its light safe bottle and injected it into the gum. Mix, mix, mix.

The next step is tricky, and critical. The emulsion needs to be coated evenly and smoothly onto the water color filling the area that will be covered by the negative. I use two Hake brushes. One for the first coat. Big, fast, accurate strokes are required to get an even coat before the emulsion starts to gel. Brush strokes and brush hairs are the enemy. Much cursing happens at this point. So far, I am living with slight imperfections. Maybe a sponge brush would be better. The second brush is used at the point where the gel is coated and is starting to get sticky. The idea is to smooth out the surface as much as possible. Long even vertical strokes, long even horizontal strokes both with little more than the weight of the brush touching the surface. Did I mention that the paper starts to warp from the moisture making it necessary for the brush to traverse a hilly landscape. All the while wearing rubber gloves to keep from accidentally absorbing chromium into my body.

Then the paper is hung in a dark space to dry. A fan is helpful.

The exposure then takes place in a UV lightsource box. The paper is carefully sandwiched with the negative between two pieces of heavy glass (I don't have a contact printing frame yet). The negative must be in tight contact with the paper. UV light (wavelength 370 nanometers) is dangerous to the eyes, so UV protective sunglasses are worn. After many tests and trials (hours and hours), I have settled on 1 minute exposures. Even this is not certain.

The print is then removed from the lightbox and placed face down in a water bath. It is now that things get tricky. The gum that is supporting the pigment gets soft. It has been slightly hardened where the UV light made it through the negative (shadows) but it is still very very fragile. Any slight touch on the bottom of the tray, back of the hand, thongs (I have done all of these) and you are back to square one. Yes. START OVER!

30 minutes and two changes of water later (which means three chances to ruin the print) the print can be hung to dry.

Once dried, it can be evaluated. Too light, start at the top and recoat for a second exposure. Doing a tri-color print? You are 1/3 of the way there (if you are very lucky). Oh, I forgot to mention, for multiple coats, the paper shrinks like cotton does and needs to be preshrunk at the beginning of the whole process to minimize this. That means a hot water bath and hand drying.

Are you exhausted just reading this yet?

The insanity of the process is what makes it so rewarding (maddening) I am starting to understand why so many great artists lose touch with reality.

Gumoil step test

The purpose of this test was to calibrate exposure for gum printing.

I used a 3:1 ratio of gum to sensitizer. 

The step chart goes from 100 black to 0 white in 20 steps.

I made 6 exposures from 30 seconds to 3 minutes in 30 second increments.

It was developed face down for 15 minutes with one change of water after three minutes. I then gave it a rinse with soft running water. It was put in the sun to dry before painting.

After drying, I applied a complete coverage of lampblack oil paint and then rubbed off with paper towels until it was a clear differentiation between exposed and unexposed gum. Then, after a quick soak to wet the paper, it went in a 15 second bleach. I used Clorox concentrated (8.25%) diluted to 6 percent and then mixed 1:6 with water. Another gentle rinse took it to this point.

The 30 second exposure was not enough to harden any of the gum. 1 minute showed hardening down to about 45 and 1.5 minutes down to 60. The highlights also cleared best at 1 minute.

I think about 4 more steps (of 20) were clear from the 1 minute exposure and 3 from the 1.5 minute exposure. Longer than 2 minutes, maybe only and additional step cleared and not very well. 

After drying, I attempted to apply a second coat of oil. To differentiate the two applications, I thought I would choose another color. I chose, Van Dyke Brown. I am not sure why, but it was a disaster. First it was very stick and hard to apply. Then, when rubbing it with paper towels, it pulled off paper, black oil paint and the kitchen sink. It was sticky like glue. When I rinsed it, it came right off without any bleach. Very strange indeed.i won't use that color again.

Anyway, I think that this has shown me that 1 minute to 1.25 minutes exposure works best. If less shadow is desired, the negative could be leveled to lift them to around 85 (from 100).

gumoil with halftone negatives test

Unfortunately I used negatives instead of positives (positives are required for gumoil prints to be positives). I think they look pretty good. The 50 lpi looks like it has better gradients than the grayscale. I am almost convinced, that for gum printing, halftone is the way to go.

From left to right: grayscale, 50 lpi, 25 lpi, 12 lpi halftone screens

gumoil prints

Here are a few gumoil prints of sunrise at Angkor Wat in Siem Reap, Cambodia

1.5 minute exposure. Highlights cleared in first bleach bath (etching) and then a coat of Payne's Gray.

2 minute exposure. I left this one in the bleach a bit too long and all the gum cleared. I left the highlights as they were.

45 second exposure. My favorite. The bleach cleared just enough for the second color (Payne's gray) to fill in. The second bleach then cleared the highlights in the clouds and the waterlilies.

Anyone who knows Angkor Wat will recognize that I forgot to reverse the positive before printing and ended up with a horizontally flipped image.