Tod Gangler (artandsoul@mindspring.com)
Thu, 07 Oct 1999 10:24:04 -0700
And now, for all those fans of Carbro who have been breathlessly waiting,
here is a version of the Vivex B Carbro sensitizer that worked extremely
well for me with Kodak's Fine Grain Positive film, once upon a time:
Solution A: mix the following in 1 liter of water:
50 gm Potassium Ferricyanide
50 gm Potassium Bromide
15 gm Ammonium Bromide
Solution B: mix in 1 liter of water:
15 gm Chromic Acid
Solution C
15% Chrome Alum solution
To make 250 ml. of sensitizer, mix (50 ml Sol. A) + (12-30 ml Sol B) + (10
ml Sol C). Use this sensitizer at 60 degrees F.
I used to soak my tissue in cold water for 1 minute, then squeegee onto
glass. Then I would sensitize the tissue in a tray for 2 min. 45 seconds.
I would lay the film positive on glass and wet with 1/10% acetic acid (3 ml
acetic acid per 1000 ml water.) I would roller-squeegee the tissue into
contact with the film positive and leave the sandwich together for 15
minutes. Then, removing the tissue, I would combine it with a final
support sheet for 20 minutes before immersing in a tray of hot water,
peeling the tissue off, and processing.
Most of the Carbro sensitizer recipes that use chromic acid are two part
sensitizers, where the tissue is immersed separately in each for varying
periods of time to achieve different effects. In this recipe, all 3 parts
are combined into a single sensitizing bath, however the proportions of the
recipe may be changed to achieve some of the control that the 2-part
sensitizers offer. Briefly, adding more Chromic Acid will produce a
lighter image with less relief, and using less Chromic Acid gives a darker
image with more relief. The amount of Chrome alum needs to be carefully
adapted to the hardness or softness of the gelatin in the pigment tissue.
Using more than 15 -20 ml of 15% Chrome Alum solution per 250 ml total
sensitizer solution will probably overharden most tissue.
Good luck,
Tod Gangler
Seattle, Washington
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