A blended ferrocyanide print process

[BJ68]

I also had to add Ammonium Chloride to Part A, as the Cyanotype was lifting off from the paper.

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]

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

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..

 

[Raghu Kuvempunagar]

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.

This probably won't work because if you print cuprotype first. Cyanotype sensitizer will replace copper with iron as the second sensitizer is coated - not unlike the iron toning of cuprotype as discussed by @fgorga here.

To combine the two, cyanotype should be the first layer, then cuprotype as I showed here.

:Niranjan.

@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.

 

[Raghu Kuvempunagar]

@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.

 

[nmp]

@nmp:

Below is a pic of Cuprotypes coated with Simple Cyanotype sensitiser (pic was taken thirty minutes after Cyanotype coating).

View attachment 395246

On the left is a processed Cuprotype print coated with Simple Cyanotype sensitiser and on the right is exposed Cuprotype print also coated with Simple Cyanotype sensitiser.

By processed Cuprotype print I mean coated, exposed and developed (in dilute Citric Acid). And by exposed Cuprotype print I mean coated and exposed but not developed.


I don't think I can ever get regsitration by eye right, but here is an example print from process #2 as discussed in my earlier post. First layer Cuprotype and second layer Cyanotype.

View attachment 395248

And here is another from the past:

View attachment 395249

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.

 

[Andrew O'Neill]

@Raghu Kuvempunagar I've been using the Copper Sulphate developer at a 1+5 dilution. Would changing the dilution have an effect on tone colour?

 

[Raghu Kuvempunagar]

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

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.

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

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.

 

[Jan de Jong]

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.

 

[Raghu Kuvempunagar]

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.

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]

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.

 

[Raghu Kuvempunagar]

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.

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]

BTW there is another Copper Toner which is essentially Copper Sulphate complexed in Ammonia.

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]

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

 

[Raghu Kuvempunagar]

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.

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]

raising the NaCl concentration from 10% to 20% did not reduce the stain.

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?

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.

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]

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]

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.

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.

 

[Raghu Kuvempunagar]

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)

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]

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]

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.

 

[xiaruan]

 

[Raghu Kuvempunagar]

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.

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?

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.

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?

 

[Andrew O'Neill]

Very cool, @xiaruan!

 

[xiaruan]

这很有趣 @xiaruan！！感谢您进行此测试并分享您的结果。

我之前已经用上面的步骤 1-3 做了测试，但没有用过氧化物做过氧化（上面的步骤 4）。同样在之前的文章中，我讨论了我为验证普鲁士白和硫酸铜之间假设的氧化还原反应而进行的一些测试。在这些测试中，我也没有尝试用过氧化物进行氧化（您的步骤 #4）。在我的测试中，我没有发现在蓝晒照片中添加了亚铁氰化铜。我应该尝试用最终氧化（您的步骤 #4）再次进行这些测试，看看是否有不同。您是否在步骤 #3 和 #4 之间用水冲洗打印件以去除多余的硫酸铜？




我还有一些额外的评论：
1. 阶梯片似乎只有黄棕色调，没有任何蓝色。这是因为普鲁士白矿全部都转化为亚铁氰化铜吗？
2. 您能否分享步骤 #3 之后的打印照片？即在用过氧化物最终氧化之前。3. OP 中的过程不使用氧化剂，但发生了亚铁氰化铜的图像添加。因此，如果机制确实相同，我想知道为什么不需要氧化剂呢？或者，敏化剂中额外的铁氰化物可能充当了必要的氧化剂？

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]

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.)