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.
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Hershel’s Original Cyanotype Formula
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Solution A
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Ammonio-citrate of iron
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20 parts
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Water
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100 parts
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Solution B
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Potassium ferricyanide
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16 parts
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Water
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100 parts
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Equal quantities of A and B are mixed just before use.
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A “Modern” Cyanotype Formula
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Solution A
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Green ferric ammonium citrate
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110 grains
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Water
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1 ounce
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Solution B
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Potassium ferricyanide
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40 grains
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Water
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1 ounce
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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.
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Dick Sullivan’s Recommended Formula
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Solution A
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Green ferric ammonium citrate
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27.2 grams
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Oxalic acid
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0.5 grams
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Water to make
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100 ml.
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Solution B
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Potassium ferricyanide
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9.2 grams
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Oxalic acid
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0.5 grams
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Ammonium dichromate
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0.2 grams
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Water to make
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100 ml.
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Lagrange Formula
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Solution A
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Ferric ammonium oxalate
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10 grams
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Oxalic acid
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1 gram
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Distilled water
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100 ml.
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Solution B
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Potassium ferricyanide
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10 grams
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Water
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100 ml.
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Use equal parts.
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C.B. Talbot Single Solution
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Potassium ferricyanide
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122 grams
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Liquid ammonia .880
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8 ml.
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Ferric ammonium citrate
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197 grams
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Distilled water
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1 liter
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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.
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Chambon Single Solution
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Gum arabic
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20 grams
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Ferric ammonium citrate
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30 grams
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Tartaric acid
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20 grams
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Distilled water
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200 ml.
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Dissolve completely and add:
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Liquid ammonia
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40 ml.
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Shake well and add:
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Potassium ferricyanide
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25 grams
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Distilled water
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100 ml.
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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.
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U.S. Liquid to Metric Measure
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Ounces
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Drams
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Milliliters
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1
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8
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29.57
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0.125
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1 (60 minims)
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3.697
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0.03381
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0.2705
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1
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Fisch Ferro-Prussiate
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Solution A
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Tartaric acid
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95 grams
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Water
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375 ml.
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Ferric chloride sol. (sp. gr. 1.45)
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80 ml.
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Liquid ammonia .880, not more than
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175 ml.
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Solution B
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Potassium ferricyanide
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70-80 grams
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Water
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270 ml.
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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.
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Colas’ Ferro-Gallic Formula
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Gelatine
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10 grams
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Ferric chloride (syrupy)
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20 grams
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Ferric sulphate
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10 grams
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Tartaric acid
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10 grams
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Water
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300 ml.
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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).
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Lietze’s Ferro-Gallic Formula
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Gum arabic
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6.7 grams
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Ferric chloride (solid)
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5 grams
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Tartaric acid
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3.3 grams
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Monsell’s salt
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3.3 grams
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Water
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100 ml.
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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).
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Nakahara’s Ferro-Gallic Formula
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Gum arabic
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15 grams
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Tartaric acid
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2 grams
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Sodium chloride
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9 grams
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Ferric chloride
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15 grams
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Ferric sulphate
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10 grams
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Water
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110 ml.
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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).
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Brown Toner for Cyanotype
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Bleach
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Sodium hydroxide
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5 grams
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Water to make
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1 liter
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Toner
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Tannic acid
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20 grams
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Water to make
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1 liter
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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.
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Uranotype
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Sensitizer
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Green ferric ammonium citrate
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110 grains
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Uranic nitrate
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35 grains
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Water
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1 ounce
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Developer
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Potassium ferricyanide
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22 grains
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Water
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1 ounce
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Caution: Uranium nitrate is highly poisonous--do not allow to come in contact with skin--wear gloves, goggles, and a long-sleeved shirt.
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Avoirdupois to Metric Weight Conversions
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Ounces
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Grains
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Grams
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0.03527
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15.43
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1
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16
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7000
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453.6
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1
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437.5
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28.35
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1
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0.0648
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