Gum Bichromate Workflow 2012 ©

MAKING THE NEGATIVE:

Image↵Mode↵8 Bits/Channel 

Image↵Auto Color

Image↵Adjustments↵Color Balance↵-35 Cyan

Image↵Adjustments↵Hue/Saturation↵+30 Saturation

Image↵Mode↵Multichannel

Split Channel

Image↵Adjustments↵Invert

Image↵Adjustments↵Levels↵Auto

Image↵Adjustments↵Curves

Apply Curve:

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MAKING THE PRINT:

Using the Cyan negative, I start with two layers of Cyanotype (old Cyanotype formula with 1% Ammonium Dichromate solution for added contrast—6 dropper stems per 20ml of liquid, 10ml A + 10ml B).  I expose enough to achieve slight tone in step 3.

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Starting with the Magenta negative I mix equal parts of Ammonium Dichromate sensitizer with Gum Arabic (12 dropper stems of each) and about and inch of pigment (Schmincke Pthalo Blue for the cyan, Permanent Carmine for the magenta and Cadmium Yellow Middle for the Yellow).

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SET 1:  I expose and develop enough to achieve slight tone in step 3 and repeat with the Yellow and Cyan negatives.

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SET 2:  I then increase the Gum to Sensitizer ratio to 13:11 (for greater contrast) and expose and develop the three layers long enough to achieve slight tone in step 8.

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SET 3:  I increase the Gum to Sensitizer ratio again to 14:10 and expose and develop the three layers long enough to achieve slight tone in step 3.

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Using the same 14:10 ratio and the Cyan negative I do a short exposure (about 30 seconds) with Lamp Black.

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