A New Cuprotype?

Raghu Kuvempunagar · 2026-04-28T00:50:06-0400

Jan de Jong said:
Emulsion
10ml dest water
2 gr FAC
1 gr Copper Sulfate
1 gr Thiosulfate

apply this to a sheet of paper, let dry.

I exposed here some flowers and the top one is the oiled paper-negative previously used for the FerroBlend. No new oil applied.
Exposure with UV 365nm flood light direct on top of the glass for 10 minutes.

Development
' Rinse very well with normal water changing the bath about 4 times.
developed from the light golden brown color with following mix.
- move the paper as little as possible ie no shaking of the tray just keep it covered with the developer. .

Jan, I noticed that you sensitiser recipe is similar to the one here, but the proportions are different. Is there a good reason to prefer one over the other in terms of speed and image characteristics? Just curious to know if you done controlled experimentation comparing one with the other.

p.s. I also noticed that you're engaged in convesation with Vincenzo in the same FB post that I shared here. That's great because you/Niranjan would be able to provide clarifications to his questions based on your experience with the process better than anyone. Let's hope the interaction throws more light about the chemical pathways of this process.

Jan de Jong · 2026-04-28T02:15:12-0400

Raghu Kuvempunagar said:
Jan, I noticed that you sensitiser recipe is similar to the one here, but the proportions are different. Is there a good reason to prefer one over the other in terms of speed and image characteristics? Just curious to know if you done controlled experimentation comparing one with the other.

p.s. I also noticed that you're engaged in convesation with Vincenzo in the same FB post that I shared here. That's great because you/Niranjan would be able to provide clarifications to his questions based on your experience with the process better than anyone. Let's hope the interaction throws more light about the chemical pathways of this process.

Interested by the pfd by Vincenzo, I wanted to do some quick tests, to see if we have a process only reacting with the paper fibers or a solid forming somehow. I wanted to make a strong solution and keep it simple for my test. I think my initial recipe was more 2gr FAC 1 gr copper sulfate and 0.5 gr Thio. So for now reason I took above. Just made sure I noted it down. For the tests I used a UV Floodlight direct on the glas, so exposure is between 7-10 minutes only then. I tried to get an idea first with some tests and the UV flashlight, but noticed the sensitivity is very low, probably 5 - 10 times less than normal cyanotype with this recipe.
Having some samples thereafter, I noticed Vincenzo mentioned that after exposure the color should be dark brown when it was a solid forming. He seemed to have found that is not the case. So for that reason I added my samples from after exposure and after wash in that post.
Then the "development" with K-Ferri + K-Ferro mix solves the problem of the clearing. The print will develop in the dark chocolate brown, the whites will be almost stay white. (same as in the 2 color example I posted in this tread earlier)

Certainly very interesting all. My basic interest is : Making a solution, which can be influenced under the action of light. So atom/ molecule A + B + light -> give solid - for image. requirement should not use dangerous chemicals.

nmp · 2026-04-28T09:41:01-0400

Jan de Jong said:
Interested by the pfd by Vincenzo, I wanted to do some quick tests, to see if we have a process only reacting with the paper fibers or a solid forming somehow. I wanted to make a strong solution and keep it simple for my test. I think my initial recipe was more 2gr FAC 1 gr copper sulfate and 0.5 gr Thio. So for now reason I took above. Just made sure I noted it down. For the tests I used a UV Floodlight direct on the glas, so exposure is between 7-10 minutes only then. I tried to get an idea first with some tests and the UV flashlight, but noticed the sensitivity is very low, probably 5 - 10 times less than normal cyanotype with this recipe.
Having some samples thereafter, I noticed Vincenzo mentioned that after exposure the color should be dark brown when it was a solid forming. He seemed to have found that is not the case. So for that reason I added my samples from after exposure and after wash in that post.
Then the "development" with K-Ferri + K-Ferro mix solves the problem of the clearing. The print will develop in the dark chocolate brown, the whites will be almost stay white. (same as in the 2 color example I posted in this tread earlier)

Certainly very interesting all. My basic interest is : Making a solution, which can be influenced under the action of light. So atom/ molecule A + B + light -> give solid - for image. requirement should not use dangerous chemicals.

Here is a link to an interesting set of experiments regarding reaction between copper sulfate and sodium thiosulfate where the outcome is dependent on the variables such as ratio of the two, concentration and time. A solid product is obtained when the reactants are in higher concentration which does not dissolve once formed. Perhaps that might be the clue to what is going on here. My earlier conjecture was based on this article but then I couldn't find it.

:Niranjan.

nmp · 2026-04-28T09:44:12-0400

Raghu Kuvempunagar said:
Jan, I noticed that you sensitiser recipe is similar to the one here, but the proportions are different. Is there a good reason to prefer one over the other in terms of speed and image characteristics? Just curious to know if you done controlled experimentation comparing one with the other.

p.s. I also noticed that you're engaged in convesation with Vincenzo in the same FB post that I shared here. That's great because you/Niranjan would be able to provide clarifications to his questions based on your experience with the process better than anyone. Let's hope the interaction throws more light about the chemical pathways of this process.

Sorry Raghu, I don't have Facebook account. I can barely read the post without Facebook locking me out.

:Niranjan.

nmp · 2026-04-28T09:49:23-0400

Jan de Jong said:
I noticed Vincenzo mentioned that after exposure the color should be dark brown when it was a solid forming. He seemed to have found that is not the case. So for that reason I added my samples from after exposure and after wash in that post.

Frankly, the color on paper sometimes has no bearing to the actual color of the pigment in the bulk. Depending on the size and resultant scattering, the observed color can be quite different for sub-micron particles. So the color of the print can not be used as a definitive proof of the presence or absence of a particular molecule.

:Niranjan.

A New Cuprotype?

Raghu Kuvempunagar

Jan de Jong

nmp

nmp

nmp

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