The “New Cyanotype” (as dubbed by Mike Ware, but also known as the Ware Cyanotype) (see note 1)
This recipe was formulated by Mike Ware in response to solve some frustrations that he and I experienced with the traditional recipes, which include low sensitivity (resulting in long exposure times), the image tending to wash out during processing and stained highlights.
The main difference between traditional approaches and this formula is the use of Ammonium iron (III) oxalate, the preparation of solutions at high temperatures and the subsequent removal of excess Potassium Iron (III) Oxalate by filtration. The resulting sensitizer has an extensive shelf life and renders rich blue tones.
There is one further modification from the traditional methods, which is to add 1 to 2 drops of 40% citric acid solution per 1 cc of sensitizer just prior to coating a sheet of paper.
CHEMICALS FOR PREPARING NEW CYANOTYPE SENSITIZER
- Ammonium Iron(III) Oxalate (NH4)3[Fe(C2O4)3].3H2O
- Potassium Ferricyanide K3[Fe(CN)6]
- Ammonium Dichromate (NH4)2Cr2O7
0.1 g (see note 2)
- Distilled water to make
- Citric acid C6H8O7
- Distilled water
- Citric acid for processing prints
The following items should be on hand: a weigh scale, various small heat-resistant glass cylinders, stirring rods, a heating device or sustained temperature water batch, small funnel and no. 1 or coffee filter, dark amber storage bottles, and a UV-proof work space with good ventilation.
GPR Grade (98-99%) purity for all chemicals is adequate.
PREPARATION OF SENSITIZER
NOTE: All the usual chemical laboratory procedures and precautions apply when preparing these solutions. Work in a well ventilated space, wear protective goggles and gloves, and do not ingest the ingredients. Follow the instructions carefully and in the exact sequence listed below. This work should be carried out under tungsten light, not fluorescent or daylight. All solids should be carefully weighed, labeled and set aside ahead of mixing into solution.
- Measure out 20 cc of distilled water and heat it to about 70 °C (160 °F). Slowly add 10 g of Potassium Ferricyanide, stirring until completely dissolved. Maintain this solution’s temperature.
- Measure out 30 cc of distilled water into another beaker, and heat it to ca. 50 °C (120 °F). Slowly add 30 g Ammonium Iron(III) Oxalate, stirring until completely dissolved.
- Add 0.1 g of solid Ammonium Dichromate (OR see note 2) to the Ammonium Iron(III) Oxalate solution and stir until completely dissolved. Mix thoroughly.
- Carefully add the hot Potassium Ferricyanide solution to the Ammonium Iron(III) Oxalate solution, and stir well. Set the solution aside in a dark place to cool to room temperature for about one to two hours, during which time the solution will crystalize.
- Separate most of the liquid from the green crystals by filtration (Whatman no. 1 paper, but coffee filter paper will work). There will be about 15g of green, Potassium Iron(III) Oxalate, crystals remaining behind in the filter paper. This should be handled and disposed of safely since it is somewhat (but not dangerously) poisonous. At the end of this stage, the volume of solution should be around 60-62 cc.
- Add distilled water at room temperature to the yellow-green coloured solution to make up to a final volume of 100 cc.
- Filter the sensitizer solution one more time with fresh filter paper and store it in a labelled brown bottle kept in the dark. The shelf life should be at least 4-5 years.
- Measure out 10 cc of distilled water at room temperature, and add 4g of Citric Acid. Stir until dissolved. Store in another labelled bottle.
- Select, clean, and mark paper. Note the date and print # in pencil in the margin area.
- Measure out sensitizer: 0.4 ml for 4×5″, 0.6 ml for 5×7″, or 1.6 ml for 8×10″ areas, add 1 to 2 drops of 40% citric acid solution per 1 cc of sensitizer
- Tape the paper to the coating surface.
- Prepare the coating rod, layout out clean sheets of paper tissue for cleaning the rod and blotting the paper.
- Syringe up the solution, lay down a line of sensitizer and begin coating. Draw the coating solution into a syringe
- Blot the excess coating with a paper towel strip.
- Rinse and dry the coating rod.
- Let the coated paper sit for 1 – 2 minutes, until the shine of the coated surface dulls. Dry the coated paper for 5 minutes in a 100 degree F. stream of air.
- Assemble coated paper and negative in a contact frame.
- Expose the print to UV (artificial, peaking at around 420nm or direct sunlight).
- Inspect and continue to expose until the high values just appear green, the mid-tones are blue, and the shadow tones are substantially reversed to a pale grey-blue, giving the image a solarized look.
- Immerse the print face down in a 1% w/v citric acid bath for 1-2 minute. 1% w/v Sulfamic acid may be used as a substitute. replace after ten 8×10″ prints per 1 liter.
- Rinse the print.
- Gently wash the print face up for 15 minutes.
- Drain the print on a vertical piece of glass for 10 minutes.
- Air dry the print on a screen.
- – optional – Press the print to flatten in a dry mounting press and/or calender in an etching press.
Note 1: All of these procedures are based on Mike Ware’s extensive work, http://www.mikeware.co.uk/mikeware/New_Cyanotype_Process.html back
Note 2: If you can’t weigh out such a small amount, prepare a 20% w/v Ammonium Dichromate solution by dissolving 2 g of the solid in distilled water and making up to a final volume of 10 cc. Then, add 0.5cc of this solution to the Ammonium Iron (III) Oxalate solution at “Preparation of Sensitizer step 3“.