That printing was pretty much what I could extrapolate from the book's description of the process. That first print was a four color print; cyan, yellow, magenta and finally black. The final image was amazingly good, considering image colors and textural detail. What I didn't have yet was the understanding about printing to the light. My son was wearing a white sweater, with little textural detail, leaving mostly a zone 8 white. As a first trial run, it wasn't bad. I will post that image, after I make a digital photo copy decent enough to show.
The gum print image I am posting today was probably the fourth or fifth print I made at the time. As I have noted before, there are levels of variables that control the final print image. One of those variables is sizing. Sizing is important. The principle of making an optimal gum print has to do with keeping the gum layers connected to the paper base, referred to as the paper's "tooth". This doesn't necessarily mean a rough feeling paper. It has to do with the paper's fibers and how that paper is sized. As a substrata, the paper/gum contact is not continuous in all areas. Think of this relationship relating to density range/tonal range of the negative to gum layers being affected by the UV light.
I tend to print the black layer first, for two reasons. The first being it not only sets up the framework of the image, showing enough to know what the image is, and secondly, it also indicates the print time/float time relationship. A good sturdy black in a scene is usually from zone 1 through zone 3; dMax black (zone 1) up through zone 3, or the shadow area with detail. The printing process proceeds in the same relationship as densities in a negative during development. Zone 1 arrives first, before zone 2 arrives at that density, then zone 3 density develops in, right through zone 7, in order. Once the development of the negative reaches zone 5, zone 1 thru zone 4 is permanent, and no amount of further development will alter their densities. This is the same process procedure for gum printing.
As in the development time of a negative only controlling the highlights, by variation of time, so works the gum process control of the tonal range permanence via time. The affect of UV light reaching the colloid material holding the pigment is to make that area hardened, to the extend of the amount of light reaching it. The longer the UV light falls upon the colloid the more permanent it becomes, and less affected by water; floating. What that translates to is simply that the print time affects how much of that gum layer becomes permanent, considering the affect of the float time, washing away that gum that wasn't affected by the UV light during printing.
Back to the first black layer and print time/float time. I know roughly the density range of the negative I'm using. That tells me the ball park estimate of the 'total print time'. That would refer to that print time that holds zone 7 in place during floating, with a 2-3 minute float time washing away excess gum and leaving just enough in the highlights to leave textural detail, and nothing more. Printing to the light. Extrapolate from that and we arrive at estimates for print time for black, up to zone 3. If the 'total print time' is say twelve minutes, which would make everything pretty much permanent up to zone 7, then the first pass using black, the print time I would use would be somewhere around 5-6 minutes, depending on how much black I want to show up in the final image.
More control variables show up in the floating process, being there is float time, and float temperature considerations. I begin with the coldest tap water possible because if the cold water isn't floating off enough of the gum layer as you might like, then warming the water increases the affect of the floating, considerably. If I begin with water temperature around 70 degrees and that isn't removing enough gum, then I heat the water to 80 degrees and float 30 seconds to 1 minute and reevaluate. If not enough, warm the water to 90 degrees and continue. If that doesn't get it, then you go to warm water and an artist's brush, for direct manipulation. The tricky part of that procedure is that using this method tends to remove most if not all gum you are brushing, unless a very soft brush loaded with water, for the least amount of gum removal as you brush. Another option is using something like a water pick or any controllable way to softly run water over the surface of the print, with ability to alter water temperature.
The print I am posting here is an experiment in sizing. I had begun with a single sizing using Knox Gelatin at 2 1/2%. That offered up a fairly good surface for that first gum. I began double sizing the paper using 2 1/2% solutions each dip. This print was made using a 5% gelatin solution in a single dip. The question being, is a 5% sizing equal to (2) 2 12% dips. It does. The gum connected to the paper without as much tooth, staying on the surface sufficiently to become visually evident, as can be seen in the image below. This is the only image I made using this sizing. All of the early gums were made using a paper negative.
Gum Dichromate Print
"Fern Ridge at Sunset" ~ 5x7 ~ Unique
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