RE: Jim Patterson Cuprotype
Are there and examples of Cuprotypes on the web you can point us to?
From: Christina Z. Anderson firstname.lastname@example.org
Date: Mon, 15 Oct 2007 08:40:54 -0600
Subject: Jim Patterson Cuprotype
As I mentioned before, when assisting the Lewis bromoil workshop at Penland
this summer, I had a delightful student named Jim Patterson from New
Jim has been a photographer since a small child, working with alt processes
of all sorts. He was very much into photo chemistry and is a physician who
does occupational hazard medicine. He was like a walking tome of chemistry
information, and at the end of the workshop even typed up several pages for
all participants of the hazards of each chemical we talked about.
He kindly shares his formulas and notes on his development of the
below, and has said I could share it with the list. I could never get a
hold of Bernie Bertridge, as his email address didn't work, so I have no
idea if this formula is in any way like his.
Jim has sent me a bunch of step wedges he printed in the processes, which
the paper, below, refers to, if that doesn't make sense to you.
Jim suggested it might be an option to do a cyanotype, then a cuprotype,
then a layer of gum to do a tricolor cyanocuprogumprint. If we can't seem
to name tricolor gum over cyanotype (or is it tricolor gumover cyanotype?)
think of what fits this one will give us.
Please respect Jim's research by crediting him if you use this formula
anywhere. All notes are copyright him.
CUPROTYPE (Obernetter's Process, Ferrocupric Process, Copper Print)
by Jim Patterson 10-5-2007
J. B. Obernetter developed his process in 1864. The original formula is
noted in Jan Arnow's "Handbook of Alternative Photographic Processes",
1982, page 113.
"Copper Print" is from a 1978 Popular Photography "How to" guide. See
http://pinhole.stanford.edu/cp.htm for details.
GENERAL: A contact printing photographic process analogous to Cyanotype;
full size negative, print frame, UV exposure. The image is reddish-brown
copper ferrocyanide. All solutions are w/v (weight in a final volume),
dissolving each salt completely before the next is added, in 10% less water
than the final volume. Make up to final volume when all salts are
dissolved. Use very pure chemicals and distilled water, and plastic or
glass trays, vessels, stirring rods, etc. Try these processes at your own
risk. The chemicals can cause property damage, environmental damage,
personal injury, or even death. Store the stable solutions in brown glass
bottles, plastic caps, plastic cap liner (corrodes metal). Damp coated
paper (high humidity) may damage negatives. Use kitchen plastic wrap
between the negative and paper if needed. Sunlight and florescent light
the coated paper. Agitate trays during processing.
PATTERSON'S modified Obernetter's Process (MO3)
SENSITIZER: 100 ml distilled water
(Stable) 12grams ferric ammonium citrate (green)*
12 grams copper sulfate, hydrated (CuSO4.5 H2O)
*ferric ammonium oxalate & ferric oxalate do not work; precipitate
Light sensitive component; mix in safelight area (yellow bug light,
DEVELOPER: 1000 ml distilled water
(stable) 10 grams citric acid (hydrous or anhydrous)
10 grams ammonium thiocyanate (NH4SCN)
(can substitute potassium- or sodium-
Or make a 10% C.A, 10% A.T. stock solution and dilute 1 part stock
9 parts water.
CLEARING BATH: 750 ml distilled water + 250 ml DEVELOPER (1 part
developer : 3 parts water)
TONER: 1000 ml distilled water
(Stable) 20 grams potassium ferricyanide (K3Fe(CN)6)
(or make a 20% stock solution and mix1 part
stock: 9 parts water)
WASH: 900 ml tap water + 100 ml white vinegar, or add 5 ml glacial acetic
acid (CAUTION: noxious fumes) to 955 ml water. If your tap water has
use distilled water to avoid blue staining. This is a 0.5 % acetic acid
Coat paper with sensitizer in a darkened room with yellow bug light or low
wattage tungsten lights; no fluorescent or sunlight. Dry with forced air
(fan, no heat) & expose in print frame to UV light until an image is
present. Work out your own exposure time. I have kept coated (no
dichromate) dry paper in a dark, dry place for 3 days and it works ok. I
don't know how long it lasts. I usually coat, dry, and expose the same
Adding a drop of Kodak Photoflo to the sensitizer makes it coat better.
Tween 20 might work (I didn't have any) but I'm unsure if it's compatible
Tray develop in DEVELOPER until the shadows clear of orange color and are
pale gray. About 3-5 minutes. Highlights may have a slight orange stain
the end of development. The developer will be slightly orange in color
(iron salts). One shot developer. Do not save or reuse.
Place directly into CLEARING BATH, series of 3 tray or solution changes,
until highlight are clear (paper white) and solution is clear. If you
get all the orange out (iron salts) the print will be blue stained in next
step. About 5 minutes, longer with thick or unsized papers. The image is
now copper (I) thiocyanate, which is a dye mordant. (You can stop at this
point and dye-tone the image with basic dyes (methylene blue, basic brown,
basic fuchsin, etc) in a 2.5 % acetic acid dye bath (0.1% dye). Wash in a
2.5% acetic acid wash and dry. 2.5% acetic acid is 1 part vinegar : 1 part
water.) Or continue on for the Cuprotype if you are not dye toning.
Place directly into TONER until fully toned to reddish brown image (About
15-20 min). The image is now copper ferrocyanide.) A tray of toner can be
used for more than one print but discard when it slows, and do not pour
into the stock bottle. The thiocyanate from the prints causes it to break
down. Discard at the end of a work session.
Transfer to WASH, 3 or more tray or solution changes until highlights are
clear and solution is clear. Check the back of the paper. About 10
minutes. Thick papers clear slowly. Thin or dip sized papers clear
If your tap water is alkaline or hard, final wash in distilled water +
vinegar as above.
Dry and marvel.
CONTRAST CONTROL: Do NOT use potassium chlorate, as the copper chlorate
that forms is EXPLOSIVE when dry!!! It may be better to tailor your
negative to the characteristic curve with 1 drop dichromate to clear the
highlights. I use 30% ammonium dichromate drops (CAUTION: dermatitis,
carcinogenic; handle carefully), with 0-4 drops in 2 ml sensitizer.
Ammonium persulfate and hydrogen peroxide do not work. (Just for your
I tried potassium chlorate in a very safe area and it didn't work either.)
PERMANENCE: USDA tests show that copper ferrocyanide used as a pigment in
outdoor fences holds up well. Probably as permanent as Cyanotype, and does
not bleach on light exposure.
AMIDOL TONING: see the Copper Print http reference. Works fast. 250 ml
water, 5 grams citric or acetic acid, 0.2 gram amidol. Soak the print for
minute, wash in the WASH and dry. It darkens dramatically to a dark warm
brown as it dries. I think the copper ferrocyanide acts as a mordant,
binding the amidol, which oxidizes to the familiar dark brown as it dries.
GALLIC ACID TONING: Brown image, lower Dmax just as with Cyanotype.
PAPER: I have used Crane's Diploma Parchment (very sharp image, no
bleeding, & ferricyanide stain clears easily). Arches Hot Press Watercolor
Paper (slight texture) and Cold Press (moderate texture) work but are slow
to clear the ferricyanide stain. (See TROUBLESHOOTING) I am sure other
papers work, but some do not. Don't use buffered paper or paper filled or
sized with calcium carbonate or magnesium carbonate as alkalis bleach the
image. Works on cotton fabric also.
TROUBLESHOOTING: Low Dmax: double coat the paper, drying between coats or
size the paper. Blue Staining: Iron contamination of solutions, iron not
cleared completely in CLEARING BATH, or toner (ferricyanide) was not washed
out of the print. Increase the clearing or wash times. If a thick paper
has a yellow ferricyanide stain after a long wash, you can soak it in a
solution of 500 ml water, 5 grams acetic acid, 5 grams zinc sulfate & 5
grams sodium sulfite, which converts the potassium ferricyanide to zinc
ferrocyanide, a white pigment used in marine paints. Then WASH to remove
excess salts and dry.
ARCHIVAL WASH: Don't! The long alkaline tap water wash will dissolve part
of the image making it fuzzy or weak. Use tray washes of dilute acetic
MOUNTING & STORING: Don't use buffered mats or papers. See PAPER above.
EXPOSURE: I use a homemade UV unit of eight, 18-inch black light bulbs
Home Depot about 3 inches from the print frame. My exposure time is about
minutes with no dichromate added. 30-150% longer with increasing
COPPER PRINT: A printing out version. Develops in water. See the http
reference. I get staining of highlights and bleeding of shadows, but
Obernetter's gives sharp prints with clear highlights.
EXPERIMENTAL NOTES: I tried the original Obernetter's formula:
ferric chloride, copper chloride, with added concentrated hydrochloric
Developer: potassium thiocyanate with added concentrated sulfuric acid and
some senstizer added (why?). Slow process, very long scale and very
difficult to clear the iron salts. Split tones with reddish brown shadows
and blue highlights were common, due to cyanotype reaction in the toner
all ferric salts not removed in washing. Almost impossible to clear the
iron with a water wash. The developer is dark blood red and can't see the
print unless you pull it out of the solution. I don't recommend it.
I first modified the formula (MO1) to use 1 % citric acid instead of
hydrochloric acid and sulfuric acid in the sensitizer and developer
respectively, and left the sensitizer out of the developer. The clearing
bath I added to get the iron out and keep some thiocyanate ion in the bath
to keep the copper (I) thiocyanate in the print by common ion effect. It
is also slow (20 min exposure) but clears the iron out easily. Very fine
grained smooth image. The 21 Stouffer step wedge gives about 18 steps.
(OM2) I next tried ferric ammonium citrate to replace the ferric chloride
with a great increase in speed and about the same long scale on step wedge.
(OM3) is the process above, with ferric ammonium citrate and copper
If you have very long range negatives, such as an older process with glass
negatives, the long range of the process without dichromate may match well.
The best print is probably from a long range negative with 1 drop
in the sensitizer to keep the highlights clear and the scale matching your
negative. Photoshoping the image to match the scale of the process will
probably work great. With very high dichromate levels the print is
and much longer exposure.
The Copper Print is analogous to the New Chrysotype by Mike Ware, in that
the potassium ferricyanide and copper sulfate are mixed together as the
sensitizer and the process is mostly a printing out one with washing
(developing) in water. But without ligands (complexing agents) like
citrate, acetate, etc., the copper precipitates as copper (II)
just as gold does in chrysotype without the 3,3 dithiopropionic acid
I tried disodium EDTA alone, sodium citrate (tribasic) alone, ammonium
citrate (tribasic) alone and combinations with sodium acetate as in the
reference. The starting weight ratio of copper sulfate, hydrated, to
citrate is 1:4 which is also about the molar ratio. Speed is fast, but
staining of highlights and bleeding is a problem, just as with the New
Chrysotype with low ligand ratios. By increasing the ratio to 1:5 and 1:6
the staining of highlights is reduced and the contrast is increased, but
Dmax is decreased and exposure is increased, just as with the New
Chrysotype. Also, as with New Chrysotype, the Copper Print sensitizer is
unstable after mixed and must be coated, exposed and washed (developed)
quickly. I never got prints as sharp and clean with this process as with
the modified Obernetter's. I also had great difficulty with ammonium
persulfate causing a precipitate (potassium persulfate was worse.)
dichromate worked better for me.
I also coated paper with ferric oxalate 10 % solution and exposed. Very
fast exposure. (1 min.) This can then be placed in TONER directly for a
cyanotype, or transposed to copper ferrocyanide by using a reagent of
sulfate, complexed with citrate (1:5 sodium citrate) and ammonium
thiocyanate The reagent is unstable after mixing and must be kept in
separate bottles and mixed just before use. It is slow to convert to
(I) thiocyanate, and then it is cleared and toned just as for Obernetter's.
The image tends to be grainy. Obernetter's has stable reagents and is
faster to complete.
The image is redder, grainier, & printing speed faster with increasing pH
of the sensitizer used. I like the color of the modified Obernetter's
detailed above. Lower pH sensitizers respond to smaller doses of
dichromate. Higher pH sensitizers take a lot of dichromate to modify
contrast. GOOD SOUPING! I know you real photographers can make great
images with these processes.
Christina Z. Anderson
Assistant Professor, Photo Option Coordinator
Montana State University, VCB 220
Bozeman Montana 59718
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