Cyanotype and Other Ferric
Non-Silver Processes

by Ed Buffaloe

There are a myriad of different blue print formulae:  virtually every ratio of ferric ammonium citrate to potassium ferricyanide has been tried at one time or another.  Early on, the brown form of ferric ammonium citrate was used, but today the green form is used exclusively as it is more sensitive and produces a longer tonal scale.  Most of the ferric non-silver processes, other than cyanotype, have fallen out of use, but I provide them here in case anyone should wish to experiment with them.

The two cyanotype solutions keep indefinitely, stored in brown glass bottles.  Bacteria tends to grow in Solution A.  Simply filter it before use.  Coat with a rod or brush.  Double coating is recommended for greater depth.  Air dry or use very low heat.  Almost any paper can be used, but best results are had with non-buffered papers (i.e., papers that are still somewhat acidic) such as Arches Platine, Crane’s Platinotype, or Whatman’s.  Cyanotypes must have an acidic environment, or they will fade, so they are generally mounted on non-buffered mount board.

Negatives should be somewhat contrasty, in the 1.2 to 1.4 density range.  Exposure is made in sunlight or under an ultraviolet lamp.  Print very dark, as the image is reduced considerably in the wash.  Wash in tap water.

Toning is possible.  Though not necessary for permanence, toning can give interesting variations on print color.  A 5% solution of lead acetate is said to give a deeper ultramarine color or sometimes a grey or violet color (at longer toning times), though the solution is quite toxic.  Tea and coffee are also used as toners.  A teaspoon or two of instant coffee in a liter of water is my favorite toner.  Christopher James has a lengthy section on toning in his book.

 

Hershel’s Original Cyanotype Formula Solution A Ammonio-citrate of iron 20 parts Water 100 parts Solution B Potassium ferricyanide 16 parts Water 100 parts Equal quantities of A and B are mixed just before use. A “Modern” Cyanotype Formula Solution A Green ferric ammonium citrate 110 grains Water 1 ounce Solution B Potassium ferricyanide 40 grains Water 1 ounce Filter before use.  Use equal volumes of A and B, and develop in running water.  If the water is alkaline, a little citric acid should be added to counteract the alkalinity, which should be followed by a final wash in two or three changes of plain water. Dick Sullivan’s Recommended Formula Solution A Green ferric ammonium citrate 27.2 grams Oxalic acid 0.5 grams Water to make 100 ml. Solution B Potassium ferricyanide 9.2 grams Oxalic acid 0.5 grams Ammonium dichromate 0.2 grams Water to make 100 ml. Lagrange Formula Solution A Ferric ammonium oxalate 10 grams Oxalic acid 1 gram Distilled water 100 ml. Solution B Potassium ferricyanide 10 grams Water 100 ml. Use equal parts. C.B. Talbot Single Solution Potassium ferricyanide 122 grams Liquid ammonia .880 8 ml. Ferric ammonium citrate 197 grams Distilled water 1 liter Dissolve the ferricyanide in the water and let stand a few hours.  Add the ammonia, then the ferric ammonium citrate, and stir with a glass rod. Chambon Single Solution Gum arabic 20 grams Ferric ammonium citrate 30 grams Tartaric acid 20 grams Distilled water 200 ml. Dissolve completely and add: Liquid ammonia 40 ml. Shake well and add: Potassium ferricyanide 25 grams Distilled water 100 ml. Mix thoroughly and allow to stand for a quarter of an hour before use.  Print color is improved by a solution of 50 ml. eau-de-javelle in a liter of water.  (Eau-de-javell is also known as sodium hypochlorite, ozone bleach, and Labarraque’s solution.)  To make:  add 1 ounce sodium carbonate to 4 ounces of water, shake well; then add 320 grains of bleaching powder [chloride of lime], shake well again and filter out the residue.)  This can probably be made into a two-solution formula by separating out the last two ingredients.  U.S. Liquid to Metric Measure Ounces Drams Milliliters 1 8 29.57 0.125 1 (60 minims) 3.697 0.03381 0.2705 1 Fisch Ferro-Prussiate Solution A Tartaric acid 95 grams Water 375 ml. Ferric chloride sol.  (sp. gr. 1.45) 80 ml. Liquid ammonia .880, not more than 175 ml. Solution B Potassium ferricyanide 70-80 grams Water 270 ml. Dissolve the tartaric acid in the water, add the iron solution, then add ammonia with constant shaking until neutral.  Add now the ferricyanide solution with constant shaking, cool, and store in well-corked bottles in the dark. Colas’ Ferro-Gallic Formula Gelatine 10 grams Ferric chloride (syrupy) 20 grams Ferric sulphate 10 grams Tartaric acid 10 grams Water 300 ml. Coating should be done with a fine sponge, taking off any surplus sensitizer with a second sponge, only just moist with sensitizer.   Development takes place in a gallic acid solution (one part acid in 320 parts water). Lietze’s Ferro-Gallic Formula Gum arabic 6.7 grams Ferric chloride (solid) 5 grams Tartaric acid 3.3 grams Monsell’s salt 3.3 grams Water 100 ml. Monsell’s salt is basic ferric sulphate, also known as ferric subsulphate.  Development takes place in a gallic acid solution (one part acid in 320 parts water). Nakahara’s Ferro-Gallic Formula Gum arabic 15 grams Tartaric acid 2 grams Sodium chloride 9 grams Ferric chloride 15 grams Ferric sulphate 10 grams Water 110 ml. Dissolve the gum in hot water and add the rest of the chemicals in the order given.  Development takes place in a gallic acid solution (one part acid in 320 parts water). Brown Toner for Cyanotype Bleach Sodium hydroxide 5 grams Water to make 1 liter Toner Tannic acid 20 grams Water to make 1 liter Bleach the cyanotype print until it takes on an orange-yellow color, then wash thoroughly.  Place print in toner and tone to desired color.  You can also use a mild solution of ammonia or sodium carbonate to bleach the print. Uranotype Sensitizer Green ferric ammonium citrate 110 grains Uranic nitrate 35 grains Water 1 ounce Developer Potassium ferricyanide 22 grains Water 1 ounce Caution:  Uranium nitrate is highly poisonous--do not allow to come in contact with skin--wear gloves, goggles, and a long-sleeved shirt.  Avoirdupois to Metric Weight Conversions Ounces Grains Grams 0.03527 15.43 1 16 7000 453.6 1 437.5 28.35   1 0.0648

  

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