christinazanderson at gmail.com
Sat Oct 27 13:57:33 GMT 2012
For those interested in the cyanotype toning discussion, I received an email from Jim Patterson outlining his cuprotype process and some new changes that you might be interested in. He said I could share it so here it is, below:
From Jim Patterson, New Orleans, 2012
CUPROTYPE: A photographic print of copper ferrocyanide on paper. It is reddish brown (Hatchett’s Brown pigment). This is a modified Obernetter’s Process (1864). These directions are a simplified version over my original 2007 posting and I find the Cuprotype is much more stable in alkaline solutions than Cyanotype, so a longer archival wash is appropriate at the end (a change in my opinion).
GENERAL DESCRIPTION: paper is coated with an iron/copper salt sensitizer, contact exposed through a full sized negative to UV light, and developed in 2 solutions to produce the final print of copper II ferrocyanide.
PAPER: good quality smooth hot press watercolor paper such as Arches, Fabriano, etc.
SENSITIZER: Dissolve 12 grams of Ferric Ammonium Citrate (green) and 12 grams of Copper Sulfate pentahydrate in 100 ml distilled water. Store it in a brown glass bottle.
CONTRAST AGENT: Dissolve 7.5 grams of Ammonium Dichromate in 30 ml distilled water. Store it in a brown glass dropper bottle.
DEVELOPER: Dissolve 10 grams of Ammonium Thiocyanate and 5 grams of Citric Acid in 1 liter of distilled water.
TONER: Dissolve 20 grams of Potassium Ferricyanide in 1 liter of distilled water. Store it in a brown glass bottle.
OXIDATION DYES: various older photo developers will produce an oxidation dye in the Cuprotype which is quite stable. These colors are similar to Willis’ Aniline Process and many of those images have survived 100 years.
Amidol: reddish brown color
p-phenylenediamine + pyrogallol or resorcinol: dark brown
p-phenylenediamine + catechol: warm to cool black, depending on ratio
DETAILS: (safelight area, yellow bug light or low wattage tungsten) Tape down a piece of paper on a flat level surface. Add 1-4 drops of Contrast Agent per 2 ml sensitizer for increased contrast and keeps the highlights clear. Add 1-2 drops of 10% Tween 20 solution if needed for coating smoothly. Use a coating rod or flat synthetic sable brush moistened in distilled water to coat. Dry with a fan or hairdryer on low heat.
Expose through a full sized negative to UV light or sunlight in a split back print frame.
Place in the Developer with agitation for 2 minutes. A pale gray image of copper I thiocyanate forms and the solution becomes orange (iron salts). Wash in 2-3 changes of water with a pinch of citric acid (about 1/8 teaspoonful per liter) for 1-2 minutes each until paper is clear of the iron stain (orange color). If you don’t remove all the iron salts you will get a cyanotype in the next step instead of a cuprotype.
Soak in the Toner for 5 minutes or more with occasional agitation where the copper II ferrocyanide image forms. Development can be stopped early by removing it and washing. Wash in 3 or more changes of water with a pinch of citric acid for 3 minutes each to clear the yellow ferricyanide stain from the paper. You can then do a 30 minute wash for archival purposes. If you don’t get all the yellow ferricyanide out of the paper, it will spontaneously decompose into a cyanotype in the next week.
CORRECTION: In my previous posting I advised against a long wash. Since then I have done side by side testing in sodium carbonate alkaline solutions, and cuprotypes are much more resistant to fading in alkaline solutions than cyanotypes. Adding a splash of vinegar or a pinch of citric acid helps prevent any problems if your water is alkaline.
Stop here for the Cuprotype, or continue on for other colors which are pretty stable.
OXIDATION DYES: These are oxidation dyes of the salon permanent hair dye type. These dyes increase the density and contrast, so expose/develop the Cuprotype to a lower density to avoid overexposure. These dye baths are clear but have a short life. Mix just before use. Discard when it becomes discolored. PPD and Amidol are very fine powders that suspend in the air and land on everything and you will find brown or blue-black spots on your clothes, paper, counter, etc if not very careful. Mix these agents in a different area than the clean room.
AMIDOL: see directions in Jim Patterson Cuprotype on the net.
PPD + PYROGALLOL or RESORCINOL: Dissolve 0.3 grams of Sodium Bisulfite in 100 ml warm water. Dissolve 0.5 gram of p-phenylenediamine and either 0.5 gram of pyrogallol or resorcinol in the bisulfite solution. Pour on the print and agitate for 1 minute, wash well in water to clear the developers out of the paper, and hang up to dry where the color develops by air oxidation.
PPD + CATECHOL: Dissolve 0.3 grams of Sodium Bisulfite in 100 ml warm water. Dissolve 0.5 gram of p-phenylenediamine and 1gram of catechol in this solution. Pour on the print and agitate for 1 minute where a brown color develops. Wash as above to clear the developers out of the paper and hang up to dry where the warm black color develops by air oxidation. Higher catechol concentrations cause a cooler blue-black color.
SAFETY: Use nitrile or vinyl gloves, a dust mask, an apron and safety glasses to prepare solutions. NOTE: The old photo developers and Ammonium Dichromate can cause poison ivy type skin rashes, and are toxic by inhalation, ingestion, or skin absorption. Most are carcinogens. The FDA does allow up to 5% PPD in commercial hair dye. Use gloves or tongs to process prints and don’t spill the solutions on tabletops, etc. Use a wet cloth or wet mop to clean (as opposed to dusting, blowing, or sweeping) to avoid creating dusts that can be inhaled. Clean trays etc before they dry or dark stains may result.
Christina Z. Anderson
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