The Gum Print ~ Paper Preparations

Preparing the printing paper for a gum print shapes much of how that print will appear in the end. In gum printing, the handling of paper sizing and the thickness of the gum mixture is a handshake on how the pigments will be suspended in the emulsion and bound to the paper in the finished print. It is that combination of attributes that set up how the final image will look on the printing paper. Not enough sizing in combination with too thin gum solution and the pigments stain the paper and that pretty much ruins the print. Too much sizing and and a thick gum mixture results in the image sitting on the surface, which is the explanation for the print below, a test on just how much I could get away with on the 'heavy' side, respectively. All the colors sit absolutely on the surface, in addition to losing some of the transparency in the layers, resulting in a colorful print, yet, again, with little texture or detail. What becomes obvious is that the print looks more like a Pastel than a gum. Not to my liking. It's a personal thing.

Before sizing though, I highly recommend shrinking the paper. An extra maneuver yet I believe an important one if you intend on multiple print layers. Each print layer is floated in water, and being rag, tends to shrink just a wee bit each successive dry down.

My method: I bring  1000 ml of water to 120-125 degrees. Pour into tray and begin placing the pre-cut sheets one by one in the water and let soak for at least thirty seconds. I soak mine for a minute, then pull out and let dry. I am making two 16x20 drying frames to dry paper flat and even. The reason I go the extra mile is that really good rag paper, like Platine or other good heavy weight papers, will indeed shrink under the conditions of gum printing. You want as much shrinkage on that first run to mitigate any further future shrinkage.

The sizing of a paper is part of the story. The paper is also important. The paper needs "tooth" to be well suited for gum printing. Tooth being the ability of the paper not to be too smooth, which doesn't give the gum solution much to hold on to. After each coating and printing, the gum print is "floated" in a tray of room temperature water. That part of the gum area that wasn't affected by the UV light will begin to float off the paper. That area that was affected by the UV light won't. It has become impervious to pretty much anything at that point and will only be floated off of those tonal ranges that have yet to be fully, or partially affected by UV light. This is why print time is very important to know for controlling the amount of color floated off a print, and, at which tonal value.

Left: as the gum Arabic color layer is floated away at some areas affected by UV light, it can leave areas where there is no gum, spaces where there needs to be some paper connection to the gum, to keep the gum attached to the paper base. This is where the paper's "tooth" comes in offering this bridge between gum and paper.

My personal choice for paper tends to fall on Arches 140 lb Hot Press Watercolor paper. It doesn't feel 'rough' but it does have this 'tooth', and I get very good results from it.

After the shrinkage dry down, the next step is sizing. As in gum printing itself there is leeway in sizing, in the sizing solution, and number of sizing layers. How much do you want to size the paper before printing. Knox Gelatin is probably the most used sizing in history. Arrow Root is likely close behind. Gelatin is cheap and easy to find, being every grocery store. Sizing can range from as little as 2%, up to 5%. Sizing is also recommended to be done twice. That, from the old books, and my own recommendation.

My personal choice of sizing my paper is two sizing runs of 2 1/2% gelatin solution. This was not the case with the print below. The above information was learned from the print below. 

Sizing Formula:
Gelatin Sizing; 2 1/2%

Distilled Water              280 ml
Knox Gelatin                     7 g    (1 packet)

Take 100 ml (room temperature) water ~ Add 7 g gelatin
Let sit 15 min for absorption
Add 180 ml Water @ 120 degrees to make 280 ml

*Submerge paper 30 seconds each side
For larger sheets of cut paper, or for several sheets at a time, a larger mixture can of course be made up, either doubling or even quadrupling the above formula. Know Gelatin comes in a box with four 7 gram packets. For a full mixture using all of the packets; for large paper or several sheets.

Distilled Water              1120 ml
Know Gelatin                    28 g

Take 450 ml (room temperature) water ~ add 28 g gelatin
Let sit 15-20 min for absorption
Add 670 ml Water @ 120 degrees to make 1120 ml
Same paper treatment as above.

The mixing formula for the below print is from memory, although autobiographical memory is something we don't lose over time. Making prints is autobiographical memory. As seen in the print, there is little texture and detail. There is also not a lot of tonal separation, which translates to colors sort of mooshing together, more than enhancing each other. This was an early gum print, when I was still testing the boundaries of viscosity and pigment intensity, and finding answers. The colors aren't transparent so they tend to dominate regions of the print where a density is variant from another.

Paper; Pre-Shrunk; 2 coats of 5% gelatin sizing

Gum Mixture: (approximately) 30%
4 (CYMK) color print layers

Gum Dichromate Print ~ "Sunset Fern Ridge"

1985 ~ 5"x7" ~ Unique

Vaneta, Oregon