Cyanotype process 2 - Negatives, Exposure, and Development

The cyanotype negatives are mostly 50x60 cm (about 20"x24") continuous tone black and white films that are directly exposed from positive transparencies via enlarger. They are processed in D-76 and sometimes D-19 developer, fixed and washed. This enlarger transfer step allows me to manipulate the tonal range for the cyanotype and also on occasion to create multiple exposure negatives using several original transparencies.

I have also begun experimenting with direct digital generation of full-size negatives via scanning on my Minolta Dimage II high resolution film scanner. The negative is then generated by output to high-resolution inkjet printer on transparency film. I'm limited to 8x10 for these negatives unless I do mosaic printing, spreading the image over 2 or 4 8x10s. If done carefully, this has worked fairly well, though there may be a slight line where the sections come together.

I constructed a large UV exposure unit using eight 48" UV blacklight bulbs mounted on a large frame. The negative and coated paper are sandwiched in a glass exposure contact unit which I also built. Exposure times range from 30 seconds to 5 or 6 minutes, fairly short by cyanotype standards. The time will mostly depend on the intensity of your UV source and the overall density of the negative. Overexposure is preferable to underexposure. The paper can be inspected during the exposure if the negative and paper are taped down securely. After many cyanotypes, I have begun to get a feeling for how long is needed -- the tones will actually reverse from dark back to light.

Development of the exposed paper may be either in plain water or acidified water (using acetic acid). Many researchers have reported that acidifying the developer helps to achieve higher densities (darker more intense blues) and better tonal range.

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