[] * Cyano * Van Dyke * Hypo Iron * Vitamin C * Seawater Plates

Copper Print

Below are the "original formulas" [published in the Summer 1979 issue of Popular Photography's How to Guide]. Cor Breukel has been working on improving the process though consultation with me. I have created a page for his version.

SAFETY NOTE: always wear gloves and safety glasses. I also recommend a lab coat or other outer garmet, long pants and closed toed shoes.

There are two related formulas, use the one you can get the materials for. The resulting mix is the same.

FORMULA 1, to 20ml of water add:

4.8 grams	sodium hydroxide
3.7 grams	citric acid
3.7 grams	acetic acid (glacial, 100%)
2.5 grams	copper sulfate
let cool, then add:
2.0 grams	potassium ferricyanide
0.5 grams	potassium persulfate

NOTE: add in order listed. adding acid directly to the potassium ferricyanide could result in your DEATH!

A safer way to mix this formula is:

FORMULA 2, to 20ml of water add:

5.0 grams	sodium citrate
5.0 grams	sodium acetate
2.5 grams	copper sulfate
let cool, then add:
2.0 grams	potassium ferricyanide
0.5 grams	potassium persulfate

You will need to coat starch sized paper twice or agar sized paper once.

Will take approximately 6 minutes exposure in direct sun in a contact printing frame. Your negative need to be a little stronger than for a silver print.

To fix, gently wash in water for five minutes.

To intensify:

to 250 ml of water add:

5 grams of acetic or citric acid 0.1-0.5 grams of Amidol (2,4 diaminophenol dihydrochloride)

This will not keep and needs to be made up fresh. Immerse the copper print in above until the color stops changing. (fast reaction), then wash and dry. The print will get noticably more intense upon drying, especially if you do the final drying under a household iron or in a dry mount press.

The formulas will work on cotton frabric as well. I don't know how well it will hold up to washing. As copper salts can be mildly toxic, I would not recommend for clothing.

STRANGE ADAPTATION

This is the formula for a direct postive copper print. Noticably less sharp but whiter whites.

to 25 ml of water add:

5 grams of sodium citrate
5 grams of sodium acetate
2.5 grams of copper sulfate
2.0 grams of potassium dichromate (nasty carcinogen!)

expose paper from 5-20 minutes and develop in 1% sodium ferrocyanide [NOT ferricyanide!] then wash for a few minutes in water.
 

Copper Toner

an interesting adaptation if you want to tone silver prints

selenium toning first gives different results, as do other tones before or after copper.