by Terry Holsinger
Stock Solution A
Water 100 ml
Ferric ammonium citrate 20 grams
Sometimes this solution will grow a bacterial mat.
Remove the mat and continue using the solution.
Stock Solution B
Water 100 ml
Potassium ferricyanide 8 grams
Mix 1 part A with 1 part B
The working solution is a bright yellow-green color.
Coating paper can be done under normal room lighting conditions.
Use a foam brush. Rinse it in distilled water and you can use the same brush for a long time.
Let dry in the dark. You can use heated air to speed drying.
Apply a second coat if desired and dry again.
Expose until the high midtones lose detail. They will turn a dark brownish green.
Wash until all the yellow-green is gone
Dry and display.
If any part of the unexposed coated paper begins to turn dark you most likely have:
1) a buffered paper on which the image will not form correctly and may fade as well; or
2) some other form of chemical contamination that may affect the image.
If you feel the image does not contain enough contrast, you can add a small amount of dichromate before coating. Or if the image is too light, try another coat of the working solution.
The image formed with this process is made of Prussian blue, a very long-lasting pigment; it may outlast the material it is printed on.
This process is not kind to fragile papers. The wash can take a good deal of time to completely remove all the unexposed solution.
You can coat any material that will absorb water--fabric and wood come to mind.
On the Llano County Backroads - 5x7 Cyanotype
Gorman Falls, 2002 - 5x7 Cyanotype