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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

References

John Barnier, Editor.  Coming into Focus.  San Francisco:  Chronicle Books, 2000.
George E. Brown, F.I.C.  Ferric & Heliographic Processes.  London:  Dawbarn & Ward, Ltd, 1900.
Christopher James.  The Book of Alternative Photographic Processes.  New York:  Delmar, 2002.
Bernard E. Jones, editor.  Encyclopedia of Photography.  New York:  Arno Press, 1974.
John A. Tennant.  The Photo-Miniature.  Tennant and Ward:  New York, January 1900.
 

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