A blended ferrocyanide print process

BJ68

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Andrew O'Neill said:
I also had to add Ammonium Chloride to Part A, as the Cyanotype was lifting off from the paper.
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In my experiments I used 4% gelatin with 0.2% glutaraldehyde to stabilize* the cyanotype layer see (in English) Variant 1 in https://illumina-chemie.org/viewtopic.php?p=72786#p72786 with the modification in red.
Interestingly the stability of both solution are very good: https://illumina-chemie.org/viewtopic.php?p=78036#p78036 but I think the hardening effect is here gone.....

*= Recipe was developed after a failed workshop, where the washing of the cyanotypes has only a very pale blue image given....so a very "robust" process was necessary.

With this the stabilized layer can be coated with the second solution.....im my approach.

bj68
 

Debanjan

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I follow an equivalent routine for Cyanotype stability.. I keep a 8% Gelatin solution separate. Part A and Part B of standard Cyanotype solutions. Finally I mix Part A : Part B : Gelatin in 4 : 3 : 2.5 ratio. After exposure I dip in a mild acidic bath (water + normal vinegar), followed by a short dip in Hydrogen Peroxide bath and finally a long water bath .. Prints remain stable..
 
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Raghu Kuvempunagar

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Nice prints @Debanjan and @Andrew O'Neill. Thanks for trying out the process and presenting your results.

@koraks: If you plan to use Canson Montval, please give it an acid pre-wash (followed by a water wash to remove residual acid) and skip Ammonium Chloride in the sensitiser.



@nmp: Frank doesn't use Cyanotype sensitiser for iron toning Cuprotype. I have not seen any iron toning happening when either a processed Cuprotype print or an exposed Cuprotype print is coated with Simple Cyanotype sensitiser.
 
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Raghu Kuvempunagar

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@Andrew O'Neill: the idea to use gelatine as colloid in the Cyanotype sensitiser given by @BJ68 and reaffirmed by @Debanjan is a good one. You may want to try it if you a lot of pigments are being washed out. However, I have not had the need for a colloid for smooth papers like Strathmore Bristol and Fabriano Bristol. Despite having a smooth surface, these papers work fine if Ammonium Chloride is added to the sensitiser.
 
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nmp

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Were these hypo-cuprotypes (toned with ferricyanide) to start with? Just curious...

Two very different outcomes- first one seems all cyanotype and second one seems mostly copper - paper related?

:Niranjan.
 
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Raghu Kuvempunagar

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nmp said:
Were these hypo-cuprotypes (toned with ferricyanide) to start with? Just curious...
Click to expand...

Hypo-cuprotype process is very exciting but I wasn't convinced that the image making pigment in the print is only CF. I guess there is some Copper Sulphide also there. Also, I found Cor's process to be simpler than Hypo-cuprotype process as it doesn't need a separate Ferricyanide toning step. So I didn't dive deep into Hypo-cuprotype after initial testing though the chemistry underlying the process is highly intriguing.

nmp said:
Two very different outcomes- first one seems all cyanotype and second one seems mostly copper - paper related?
Click to expand...

PMing you soon on this. A lengthy discussion on two layer prints is going to be a distraction for those who're primarily interested in OP. I suggest we carry further discussion on two layer prints over PM if you don't mind.
 
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Jan de Jong

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In order to avoid bleeding and ensure very short contact with the copper sulfate mix developer, is it an idea to apply that with a tissue or cloth soaked in the solution, perhaps apply short pressure with a brayer. Goal is to have nearly dry process before doing the development step?

Just thought of that because I want to create something where I can add the normal cyanotype and the hypo cuprotype in a dense matrix or striped alternating pattern so they do not touch.
 
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Raghu Kuvempunagar

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That looks like a good idea Jan. I have not tried applying the developer with a cotton ball or piece of cloth but no reason why it would not work. Hope it works well for you.
 

koraks

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Played around with FerroBlend a little more yesterday to see what factors may help in reducing fog. Here's a test that contains an interesting clue:

(Ignore the density difference in the image itself; the left one received one stop more exposure than the right one.)
Note how in the right print, there's a streak of fairly dense fog along the left edge of the step wedge. On the right side of the image, there's likewise a band of fog that coincides with the edge of the area I brushed the developer onto. On the left print, these artefacts are also there, but much less reduced. There's still some copper fog, but it's more subtle.

The main difference in processing was that for the print on the right, I've added some sodium chloride to the developer. The print on the left had a small amount of ammonia added to the developer. I've also done a test with both the NaCl and NH3 added to the developer (effectively creating ammonium chloride in situ), which didn't give much improvement over just the sodium chloride.

Don't ask me to explain this, but for some reason, adding just a tiny bit of ammonia seemed to work best. It's still not down to pure paper white, though. But I used a buffered paper without any pre-treatment, so buffers in the paper likely play a role.

Mind you, this is just one quick test; more systematic testing would be needed to verify if this isn't a fluke and what the optimal concentrations are.

The composition of the developer was as follows:
_ Left Right
Copper / citrate concentrate 0.5ml 0.5ml
Sodium chloride - 200mg
10% ammonia 3 drops -
Water 1ml 1ml
Development time was 2 minutes for both prints. This is actually still on the long side; I tried 30 seconds for the ammonia-developed print as well, which gave virtually identical results.
 
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Raghu Kuvempunagar

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Very interesting result! Ammonia is also a chelator of Copper like Sodium Citrate and it could be that the combination is a more effective chelator than either. It is likely that stain is inhibited due to stronger chelation. If this is what is actually happening then a chelator that's stronger than Citrate but not as strong as NTA or EDTA could reduce the stain further.

BTW there is another Copper Toner which is essentially Copper Sulphate complexed in Ammonia. I have used it in FerroBlend but the stain was quite high in the tests I did. Maybe a suitable combination of the Ammoniacal Copper Toner and the Citrate based developer with pH adjustment might work. Your test result hints at the possibility.
 

koraks

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Raghu Kuvempunagar said:
BTW there is another Copper Toner which is essentially Copper Sulphate complexed in Ammonia.
Click to expand...

This is quite interesting, also because copper carbonate is apparently involved, which brings to mind the possible in situ formation of copper carbonate on a buffered paper. It also appears that the ammonia concentration in the toner you linked to is higher still than what I tried, which emphasizes what I said about further testing being needed to determine optimum ratios.

Very interesting words about chelation btw; this may indeed be the key to getting the paper whites to clear up - maybe err on the side of too effective chelation (perhaps at the cost of slowing down development or requiring a relatively concentrated developer/toner) so that essentially most of the copper is 'locked up' as a chelate, with only some of it being released into the image. The logic I would be inclined to think of would be the opposite - have as much of the copper available to image-formation and reduce chelation to as low a level as possible. Perhaps a different perspective would be more effective. In that case, I wonder whether maybe going to extremes may help, and indeed use something like EDTA.
 

Cor

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Interesting observation, Koraks !

I played around with adding more NaCl and also KBr in the developer on Schut paper. Have yet to examine the step wedges in good light but raising the NaCl concentration from 10% to 20% did not reduce the stain.

The KBr in the developer worked somewhat better, ie less stain at 10 & 20 % (no clear difference there), but not gone.

Next is ammonia and EDTA, although I am through my allotted time and have other obligations the coming days..;-)..

Best,

Cor
 
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Raghu Kuvempunagar

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EDTA eats up a lot of PB from the print apart from chelating Copper exceedingly well. Maybe Sodium/Ammonium Citrate and a little bit of Ammonia might work well. I'll do some tests.
 

koraks

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Cor said:
raising the NaCl concentration from 10% to 20% did not reduce the stain.
Click to expand...

Yes, I've played with this a little, too, and noticed the same.

It's very interesting to read that KBr might be doing better than NaCl. Does that make a case for trying KI as well?
Raghu Kuvempunagar said:
EDTA eats up a lot of PB from the print apart from chelating Copper exceedingly well. Maybe Sodium/Ammonium Citrate and a little bit of Ammonia might work well. I'll do some tests.
Click to expand...

Hmm, good point. Well, let's see how the tests go. I must have some EDTA somewhere; I might give it a try nonetheless.
 

Cor

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Manged to print a few step wedges on Schut Paper

I tried leaving out the ammonium chloride in the sensitiser, that was a disater, spots and sliding of cyanotype emulsion, so back to adding the salt.

As my "benchmark" I used Cu developer 1+3 20% KBr which rsults in a faint but clear veil in the higher steps

Next 1% ammonium hydroxide (end conc. 1%) resulted in the same high steps but oddly shifted almost all steps towards the copper colour even steps 2 &3 unlike the KBr which stayed blue.

Than EDTA: I have a 0.5 M solution of which I added 10 µl or 30 µl to the +3 diluted developer (400 µl). It resulted in comparable results to the KBr strip. Have yet to examine them again under day light, it seemed that the EDTA ones have a slight edge over KBr (which in my hands is better than NaCl)

best,

Cor
 

koraks

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Cor said:
Next 1% ammonium hydroxide (end conc. 1%) resulted in the same high steps but oddly shifted almost all steps towards the copper colour even steps 2 &3 unlike the KBr which stayed blue.
Click to expand...

Yeah, I noticed the same thing. I did my test a few days ago and the difference seems to be permanent. I think it's due to the Prussian blue partly bleaching; it didn't quite recover entirely in the subsequent acid rinse.

The EDTA results is interesting. 10ul sounds like a very tiny droplet! Did you use a pipette? My drops are generally around 40mg or so. I've yet to try the EDTA myself; it's in a box somewhere.
 
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Raghu Kuvempunagar

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That's encouraging! I did a test with NTA but I used more than ideal - all but three steps in the step wedge print got washed out. Will test again with substantially smaller amounts.
 

BHuij

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As someone who has messed with alt process in the past (and would love to do more), but just doesn't have bandwidth for this kind of experimentation at the moment... this thread has been a joy to follow.

The process looks awesome, the results look awesome, and I will definitely be playing with the process at some future point.
 

xiaruan

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Since my native language is not English, this content was translated by DeepSeek.

I believe the principle might involve a redox reaction between Prussian white and copper sulfate, forming a copper ferrocyanide precipitate. Therefore, I designed an experiment to tone a finished cyanotype using copper sulfate. After an afternoon of testing, I succeeded, but I don’t have much time to optimize the formula. I hope everyone can help test and refine it.

What you need:

  1. Bleaching solution: 6g potassium citrate + 6g ascorbic acid dissolved in 50mL distilled water. This solution can reduce Prussian blue to Prussian white.
  2. Toning solution: 15g potassium citrate + 5g copper sulfate dissolved in 50mL distilled water. This solution converts Prussian white into copper(I) ferrocyanide.
  3. Oxidation solution: Add some 3% hydrogen peroxide to water (amount can be adjusted freely). This oxidizes copper(I) ferrocyanide into red copper(II) ferrocyanide.
Experimental procedure:

  1. Soak the finished cyanotype in the bleaching solution for 5 minutes until the image turns completely white.
  2. Rinse the paper with water to remove residual bleaching solution.
  3. Soak the paper in the toning solution for 5 minutes (or longer if needed).
  4. After removing the paper, place it in the oxidation solution to develop the red color.
Experimental results are as follows:

The resulting image produced by this method does not exhibit any surface floating effects, and the details remain exceptionally sharp.
 
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Raghu Kuvempunagar

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That's very interesting @xiaruan!! Thanks for doing this test and sharing your result.

I had previously done tests with steps 1-3 above but not oxidation with peroxide (step 4 above). Also in an earlier post, I have discussed some tests I did to validate the hypothetical redox reaction between Prussian White and Copper Sulphate. In those tests also I hadn't attempted oxidation with peroxide (your step #4). In my tests I didn't find an imagewise addition of Copper Ferrocyanide to the Cyanotype print. I should try doing those tests again with the final oxidation (your step #4) and see if it makes a difference. Do you rinse the print in water between steps #3 and #4 to remove excess Copper Sulphate?

xiaruan said:
Experimental results are as follows:
View attachment 395611
The resulting image produced by this method does not exhibit any surface floating effects, and the details remain exceptionally sharp.
Click to expand...


I have a few additional comments:
1. The step tablet appears to have only yellow-brown tone without any hint of blue. Is this because all of Prussian White was converted to Copper Ferrocyanide?
2. Can you share the picture of the print after your step #3? i.e. before the final oxidation with peroxide. 3. The process in OP doesn't make use of an oxidising agent and yet the imagewise addition of Copper Ferrocyanide happens. So if the mechanism was indeed the same, I wonder why an oxidising agent isn't needed? Or could it be that the additional Ferricyanide in the sensitiser acts as the necessary oxidising agent?
 
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xiaruan

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在步骤 #3 和 #4 之间：


我尝试用铁氰化钾代替 #4（H₂O₂ 氧化液），发现它确实很快产生了红色图像。然而，它也导致了严重的、无法去除的染色，可能是因为我在涂抹铁氰化钾之前没有彻底洗掉硫酸铜。

 

xiaruan

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I believe that excess potassium ferricyanide may have acted as an oxidizer in the subsequent reaction. The process can be optimized as follows:

  1. Bleach the finished cyanotype in the bleaching solution.
  2. Rinse thoroughly and then immerse the bleached paper in the toning solution.
  3. After toning, wash the paper thoroughly to completely remove any residual copper sulfate (unless using hydrogen peroxide for oxidation, in which case this step may not be necessary).
  4. Finally, place the cleaned paper in the oxidizing agent (either hydrogen peroxide or potassium ferricyanide) to develop the image.
(Key Insight: This adjustment ensures better control over oxidation, preventing unwanted staining by eliminating excess copper sulfate before applying potassium ferricyanide. Hydrogen peroxide remains a gentler alternative for oxidation.)
 
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