U of S | Mailing List Archive | alt-photo-process-l | RE: Gum Calibration 3 (Dark Tricolor)

RE: Gum Calibration 3 (Dark Tricolor)

By all means experiment. It is the best way to learn gum.
Just looking at you note and remembering previous posts I have a few comments.
It seems to me that diluting your stock pigment solutions with additional gum will lead you to weakly pigmented layers. I can only judge that basis my use of Daniel SMith pigments, but somehow I do not suspect that other brand contain 2x the amount of pigment. Your statement that individual layer are too dark and hence the need to add more gum leads me to the conclusion that you coating is too thick. That would also agree with your difficulty of smooting the layers out. It is just about impossible to smooth thick layers of gum.
I would suggest dilute your stock solution with dichromate 1 part stock + 1 part dichromate and skip the additional gum. Measure the amount of the mix that you use to arrive at consistent layer thickness.
FOr coating pour the mix on paper, quickly brush it in making sure it is spread all over the print and start rolling with the foam roller (I roll in one direction up and down and them side to side). Keep rolling applying less pressure as you go. You will end up with a very smooth coat (my practice is about 1 minute). If you keep rolling too long the mix gets too tacky you will start see roller marks.
The roller has to be damp, but not too wet. Try coating 5-6 sheets at a time. By the time you are done with the first sheet the roller will have the correct dampness to it and would have picked some paint for a steady state work. By the time you get to the 6 or 8th sheets you will have the feel for the coating.
If the roller becomes too wet (long rolling times) just roll it over dry paper towel.
Remember that the most creative tools for gum are the brush and sprayer bottle during development. They might help you more then overly compicated negative systems.
Have fun and keep us posted.

> Date: Mon, 27 Oct 2008 13:35:06 +0200
> From: mail@loris.medici.name
> Subject: Gum Calibration 3 (Dark Tricolor)
> To: alt-photo-process-l@usask.ca
> I mixed stok paint/gum solutions as following:
> 1. 15ml Schmincke Aureolin Modern (208) PY151 + 65ml gum = 90ml total
> 2. 15ml Schmincke Ruby Red (351) PV19 Rose + 165ml gum = 180ml total
> 3. 15ml Schmincke Helio Cerulean (479) PB15:3 + 165ml gum = 180ml total
> As you can see above, tricolor mix will consist of 2Y + 1M + 1C for
> neutral grays. (3Y + 1M + 1C is remains on the warm side with my
> paints...)
> I will dilute the paint/gum stok solution 1+1 with gum at time of use, and
> I will add equal amount of 10% ammonium dichromate solution to the working
> strength paint/gum solution; I like the consistency I get with 1 part gum
> solution (which is 1+2 gum powder+water w/w) + 1 part dichromate (v/v)
> solution...
> I will fully calibrate each color individually (using Luminosity channel
> at Lab mode), but since the paints look quite strong even at working
> strength, I will probably(!?) end up with a tricolor print that looks too
> dark when the colors are printed over each other (as noted by others
> before).
> If I end up with a print that is too dark, then I will do a final
> calibration printing all colors together (hopefully giving a balanced
> grayscale gradient), and make a curve that is going to be used before
> splitting the channels of the original(*), again using the Luminosity
> channel of the source image.
> (*) This curve will be used to lighten the image (applied to the
> Luminosity channel - in order to keep the colors intact), so that it
> prints right.
> I hope to get a print that is both colorful (no muted colors because of
> excessive paint dilution pass the optimum chroma) and luminous (thanks to
> the lightening curve)...
> David, I think this is close to what Denise Ross is doing by increasing
> saturation - but in a more controlled manner methinks...
> Short list of calibration phases:
> 1. Calibrate Y, M and C individually (= curves for individual R, G and B
> channels, uni-dimensional approach)
> 2. Print tricolor grayscale step tablet (three-dimensional approach)
> 3. Calibrate tricolor print (= curve for composite RGB image)
> Short list of negative making phases:
> 1. Apply the "composite" curve to the original RGB image
> 2. Split channels
> 3. Apply the respective "channel" curves to each channel (+ colorize - if
> using colorized negatives) and print the negatives
> I'm starting tonight, with Cyan. Will post whenever I progress. Any
> thoughts? Please warn me if I'm making an obvious mistake, since all this
> will take precious time and effort -> I want to be sure I'm not fighting
> against windmills.
> Regards,
> Loris.

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