A New Cuprotype?

[Raghu Kuvempunagar]

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]

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]

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]

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]

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.

 

[Jan de Jong]

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.

The assumption in the pdf article if I take a shortcut that it was more an adhesion of chemicals rather than a solid forming, indicating that direct after exposure not a dark color of the emulsion would support that. That was the reason why I wanted to revisit it.
For that reason I posted in the Facebook as a reply the left image, showing left, Just after exposure, and then the lighter coffee colored the wet print after wash.
The second image I just took now, so few days later. That was developed with the K-Ferri - K-Ferro mix. returning the image the much darker brown. You can see the blue staining which was a result of not washing well. On another print the next day this did not happen.
Because I wanted to have some quick tests, I put the UV floodlight direct on the glasplate, under which a dried flower but still green stem of the Narcissus flower. It seems the dried flower blocks a lot of the UV. exposure was between 7-10 minutes. It is really slow and needs a lot of UV.
I guess to get deeper into the how much thio or what effect has what tests results of different concentrations would be useful. I do think a solid is formed and it has a nice color. Just it needs a lot of UV exposure.

 

[Jan de Jong]

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.

Thank you for the link, very interesting. it gives a nice overview of the possible things that can happen. This is similar way of working I did to come to the process in the first place. I took a set of test tubes with combinations outside in the sun while reading a book in my garden. My goal was to find a combination that would change color. The successful one was the one containing in my case then the used Hypo fix solution.

 

[Raghu Kuvempunagar]

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.

TFS Niranjan. It's very fascinating how changing the proportion can affect the aqueous mixture of Copper Sulphate and Thiosulphate and even result in the formation of an insoluble compound. I can see (and appreciate) that your formulation in OP was informed by these considerations.

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

No worries.

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.

Exactly.

 

[Jan de Jong]

Today lots of sun so started exposure this morning at 9-11, on some fresh Hazeltree leaves. The paper was coated earlier this week. This seems to be good. In any case if stored dark this emulsion should hold months or longer. Just adding it here to show the K-Ferri/K-Kerro + citric acid is a good developer, keeping whites clear and making the darker areas dark. No further toning then needed. It just does take a lot of UV light to go to the max black - brown.

just for copy here my details :

The Kirlian effect is because the leaves strink under the glass in the sun in the first 20 minutes
total exposure 2 hours.

emulsion 2gr FAC 1 gr Coppersulfate 1 gr Thiosulfate 10ml - dem.water

developer 3 gr K-Ferri + 3 gr K-Ferro + citric acid till pH is 3.3 about. in 200 - 300 ml of water.

1) apply emulsion to paper like water paint paper 200gr or so, let it dry naturally, important, best to use after 24 hours. If kept in the dark you can use this for months - years it does not change like Cyanotype paper.

2) Expose with either paper negatives , negatives with dmax of min 2 or material from nature like here. See previous photos also.

After exposure the darkest areas should be dark coffee color.
3) Rinse in normal water, normally not much will come of the water will be light brown only. wash well, like 5 minutes or so.

4) You can now poor the developer over the print while it is still wet, it will slowly turn dark chocolate brown. see when you like it after some minutes 3 - 10 or more. Then poor back the developer, you can re-use it many times.

5) wash with normal water, you may add some citric acid, not sure if it is any good.

the print should perhaps color to some blue in some places, but on drying that should become dark brown again.

6) dry the print (suggestion - dry flat on blotting paper, blot of the front and let it dry slow (12 hours or so) to make sure it stays nice flat)

please let me have your feed back if you try this.

 

[Raghu Kuvempunagar]

Nice result! I particularly like the halo around the leaves. Is the longish exposure time due to the presence of proportionately more Thiosulphate (compared to the recipe in post #5)?

 

[Jan de Jong]

Nice result! I particularly like the halo around the leaves. Is the longish exposure time due to the presence of proportionately more Thiosulphate (compared to the recipe in post #5)?

Thank you, I like the result also, has good clearing of the whites and very good darks, It does not get as dark as in my FerroBlend image of "the library" but it is close.

Good question on the proportions, I think next steps would be to make some test prints with 1) no Thiosulfate, 2) smaller amount.

Also for the "developer" I could refine that further. I know the k-ferri/k-ferro acidic mix has a good effect from my previous direct positives copper involved cyanotypes. Somehow my intuition tells me that that ratio could be 2:1, but for now I stuck to 1:1.

see link Cyanotype direct positives

 

[Bexhill Darkroom]

Background:

I thought it would be a good idea to open a new thread continuing the work started in an another thread started by @Jan de Jong on possibility of a VDB-like process using residual silver content in a depleted fixer:

Cyano-vanDyke ... finding a use for used B/W fixer - did i find a new process? or is this an existing process variation?

Trying to find a new process using used hypo-fixer. This should contain silver and I have been working many experiments to see if i can release that again for some type of VanDyke print. Adding it direct will result in fainter blue. -> let me know if I have found a new process or if this is...

www.photrio.com

There it was demonstrated that a photogram can be made with a photosensitizer consisting of used film fixer, CuSO4 and ferric ammonium citrate (FAC). Questions regarding the role of CuSO4, which is obviously not a part of a typical VDB recipe, in the image formation led to the possibility that the active ingredient in the observed photo activity may also be the thiosulfate ions and not necessarily only the silver ones. Based on that, I speculated what would happen if a photosensitizer was made simply with pure sodium thiosulfate in lieu of the spent fixer. The image obtained in that case would be more akin to a cuprotype dating back to 1850’s and 1860’s (works of Burnett and Obernetter) with the most recent update by Jim Patterson:

CUPROTYPE

CUPROTYPE: a photographic print of reddish brown Copper II Ferrocyanide (Hatchett’s Brown) pigment on paper.

www.darkroomdoc.com

Upon quick examination, I found that an image did form with such a photosensitizer on exposure to UV. This was followed up with some preliminary work by me presented on that thread to look at the viability of this process. Since the scope of this work is no longer use of spent fixer and the outcome no longer a variant of VDB-like process as originally premised, I felt a separate thread will be more appropriate - where a discussion with digital negatives can also be possible.

Continuing that work, based on a starter set of sensitizer formulation and process conditions, I was able to print an actual image of what I am terming as the New Cuprotype, to differentiate it from Patterson's version. The two are similar in that they both use FAC and CuSO4 in the photosensitizer. In the Patterson process, first a Cu(i) image is formed from Cu(ii) reduced by Fe(ii), itself the result of UV photoreduction of Fe(iii), which is then converted to a grey Cu(i) thiocyanate image by developing in ammonium thiocyanate. Finally, a copper(ii) ferrocynide, also known as Hatchett’s brown, image is formed by treatment with potassium ferricyanide.

In the current process the “developer” in a sense is the sodium thiosulfate, incorporated in the photosensitizer - so no separate intermediate image is required. A strong print-out of yellowish-brown image is obtained upon exposure. The exact nature of the pigment responsible for the image at this stage is not being proposed yet, but it’s safe to say it is some form of complex between Cu(i) and sodium thiosulfate. The development is simply washing out of the un-reacted chemicals in the paper in a similar fashion as cyanotype. Unlike cyanotype though, there does not seem to be any intensification of the image from what is already printed out during exposure. Copper ferrocyanide image is then obtained by treatment with potassium ferricyanide as usual.

In short, we may have stumbled upon a new cuprotype variant - thanks to @Jan de Jong' s creative experimenting.

The print in the next post.


:Niranjan.

Fascinating post Niranjan. Is the reason why this can't be made as a 1:1:1 ratio due to the solubility of CuSO4 5H2O? Or is it more down to concentration?

 

[nmp]

Fascinating post Niranjan. Is the reason why this can't be made as a 1:1:1 ratio due to the solubility of CuSO4 5H2O? Or is it more down to concentration?

Thanks and welcome to Photrio.

Regarding 1:1:1, I don't see any reason. I also tried (see one of posts later on) 1:0.6:0.6 that apparently worked better. My initial formula was really a guess and the concentrations were what I had on hand at the time. By all means, try and see what you get. I think the order of mixing was important as otherwise a cloudy solution ensued. Please share the results here if you do experiment with different ratios.

:Niranjan

 

[NedL]

BTW, the nice reddish brown copper color of these might mean they would make good negatives themselves. They could probably be contact printed again to make nice positive prints. It would take a bit of experimentation to discover what a good negative looks like and how much exposure it needs.

 

[Raghu Kuvempunagar]

on the proportions, I think next steps would be to make some test prints with 1) no Thiosulfate, 2) smaller amount.

It would be good to find out what is the optimal proportion for keeping exposure time the shortest while producing decent DMax. No Thiosulphate might not work as the image formed after exposure might wash off without a special developer (Thiocyanate).

 

[nmp]

It would be good to find out what is the optimal proportion for keeping exposure time the shortest while producing decent DMax. No Thiosulphate might not work as the image formed after exposure might wash off without a special developer (Thiocyanate).

Without thiosulfate, ferricyanide will react with both Cu(+2) and Cu(+1) to give solid products, so no differentiation between exposed and unexposed areas will result, i.e. staining in the highlights will occur.

:Niranjan.

 

[Raghu Kuvempunagar]

Without thiosulfate, ferricyanide will react with both Cu(+2) and Cu(+1) to give solid products, so no differentiation between exposed and unexposed areas will result, i.e. staining in the highlights will occur.

:Niranjan.

I thought there's a water rinse step after exposure in both your and Jan's workflow which would remove not only the residual Cu(+2) but also Cu(+1) if no Thiosulphate is used in the sensitiser. Step #3 in post #184.

 

[Jan de Jong]

Without thiosulfate, ferricyanide will react with both Cu(+2) and Cu(+1) to give solid products, so no differentiation between exposed and unexposed areas will result, i.e. staining in the highlights will occur.

:Niranjan.

From 2022, here my result then, with FAC and Copper sulfate only. left after exposure, right after wash. What remains is the reacted FAC on the paper, the copper seems to wash off mostly without Thio. See the right picture on the top part. Also the overall was washed out.

Intuition would say, lowering the Thio like ration 2:1: 0.5 will give the impression of faster exposure when judging by the color but how about wash off and how much copper stays. I think that even with my 2 hours full sun we are not at the end of full d max, just with those time the "negative" in my example the Hazel-tree leaves will also get darker. So total contrast would stay the same. btw the Hazel-tree leaves even if they look thin are good UV absorbers, unlike the Wall-nut tree leaves which look far more dense they allow more UV through.

If I have some time I will show results at a later stage, for now I think what I have shown "here" looks to be a solid way to get good contrast and good whites.

+ adding some reference for the UV exposure:
- test prints with floodlight direct on glass about 7mm over paper 30Watt at 365nm about 10 minutes for dark brown color
- print in the sun from 9am-11am good sun, end April at 2 hours
---- gives roughly Required dose for this cuprotype recipe: ~20 J/cm² (order of magnitude) in the effective 365 nm band.


cheers
Jan.

 

[nmp]

I thought there's a water rinse step after exposure in both your and Jan's workflow which would remove not only the residual Cu(+2) but also Cu(+1) if no Thiosulphate is used in the sensitiser. Step #3 in post #184.

Yes. But I assumed you wouldn't want to do a rinse step if there was no thiosulfate due to the precise reason you outlined. Jim Patterson used thiocyanate as an intermediate to overcome this shortcoming which would form solid Cu(1) thiocyanate and other components wash away in the developer and the subsequent clearing bath, thereby creating an image contrast.

An interesting experiment would be what happens if you use thiosulfate as a developer before rinse if there was none in the sensitizer.

:Niranjan.

 

[Bexhill Darkroom]

Thanks and welcome to Photrio.

Regarding 1:1:1, I don't see any reason. I also tried (see one of posts later on) 1:0.6:0.6 that apparently worked better. My initial formula was really a guess and the concentrations were what I had on hand at the time. By all means, try and see what you get. I think the order of mixing was important as otherwise a cloudy solution ensued. Please share the results here if you do experiment with different ratios.

:Niranjan

Thanks for your response, I'll let you know what the outcome is.

 

[Raghu Kuvempunagar]

An interesting experiment would be what happens if you use thiosulfate as a developer before rinse if there was none in the sensitizer.

Indeed, and if it works it confirms that UV-induced breaking down of Thiosulphate is not necessary for the process to work.

 

[Bexhill Darkroom]

Thanks and welcome to Photrio.

Regarding 1:1:1, I don't see any reason. I also tried (see one of posts later on) 1:0.6:0.6 that apparently worked better. My initial formula was really a guess and the concentrations were what I had on hand at the time. By all means, try and see what you get. I think the order of mixing was important as otherwise a cloudy solution ensued. Please share the results here if you do experiment with different ratios.

:Niranjan

Like you I consider the exposure times to be the biggest issue with the cuprotype. I'm going to begin experiments using Ferric Ammonium Oxalate instead of FAC which i hope will significantly decrease exposure times whilst increasing tonal range. In the same way the Mike Ware cyanotype formula does. I expect three possible issues..

• Shelf stability — copper + ferric oxalate + acid in one bottle may not behave like New Cyanotype.
• Fog / background stain — more reactive iron chemistry may increase non-image stain.
• Image colour / density shift — I may get something closer to a ferrocyanide hybrid than a conventional cuprotype.

The key comparison is not just speed. It is:

speed + clean highlights + storage stability + repeatability​

 

[Raghu Kuvempunagar]

I'm going to begin experiments using Ferric Ammonium Oxalate instead of FAC which i hope will significantly decrease exposure times whilst increasing tonal range. In the same way the Mike Ware cyanotype formula does.

That sounds interesting and seems like you are all set to take up an interesting journey in the wonderful world of Copper. Wishing you the best.

Copper Sulphate and Ferric Ammonium Oxalate together in solution typically form an insoluble Oxalate of Copper. No idea if Thiosulphate in any way prevents this precipitation.

 

[Jan de Jong]

Like you I consider the exposure times to be the biggest issue with the cuprotype. I'm going to begin experiments using Ferric Ammonium Oxalate instead of FAC which i hope will significantly decrease exposure times whilst increasing tonal range. In the same way the Mike Ware cyanotype formula does. I expect three possible issues..

• Shelf stability — copper + ferric oxalate + acid in one bottle may not behave like New Cyanotype.
• Fog / background stain — more reactive iron chemistry may increase non-image stain.
• Image colour / density shift — I may get something closer to a ferrocyanide hybrid than a conventional cuprotype.

The key comparison is not just speed. It is:

speed + clean highlights + storage stability + repeatability​

You may want to check what I have posted on using tartaric acid instead of the thiosulfate . Iron-Copper a direct positive image

looking forward to your post on this.

 

[nmp]

Like you I consider the exposure times to be the biggest issue with the cuprotype. I'm going to begin experiments using Ferric Ammonium Oxalate instead of FAC which i hope will significantly decrease exposure times whilst increasing tonal range. In the same way the Mike Ware cyanotype formula does. I expect three possible issues..

• Shelf stability — copper + ferric oxalate + acid in one bottle may not behave like New Cyanotype.
• Fog / background stain — more reactive iron chemistry may increase non-image stain.
• Image colour / density shift — I may get something closer to a ferrocyanide hybrid than a conventional cuprotype.

The key comparison is not just speed. It is:

speed + clean highlights + storage stability + repeatability​

Sorry but FAO will precipitate copper oxalate at the outset. That's why I didn't use it. You can probably use some ratio of FAC to FAO to get a speedier version, but not 100% FAO (or FO.) Now I did not try and add something like sodium citrate as a ligand to overcome this precipitation, which I intended to do but never got around. Perhaps you can try that.

Good luck, you are looking at correct parameters to follow for a successful formulation of an alternative process.

:Niranjan.

P.S. Oops, didn't see @Raghu Kuvempunagar's post that says the same thing. Thiosulfate does not help clearing it up.