A blended ferrocyanide print process

[Raghu Kuvempunagar]

Thanks for the clarifications.

I'll try to replicate at my end when I get a chance hopefully soon.

 

[PGum]

I haven’t made cuprotypes in a while but in my last prints, I pre-coated the paper with a neutral 10% sodium citrate solution, then let dry. This reduced highlight staining significantly. However, I wasn’t using a development bath other then water. The formula I used was more along the lines of Cor Breukel’s approach.

 

[Raghu Kuvempunagar]

I haven’t made cuprotypes in a while but in my last prints, I pre-coated the paper with a neutral 10% sodium citrate solution, then let dry. This reduced highlight staining significantly. However, I wasn’t using a development bath other then water. The formula I used was more along the lines of Cor Breukel’s approach.

That's a great idea! The developer already has a lot of citrate and hence I didn't consider the possibility of adding it to the sensitiser or coating the paper with it prior to sensitisation as you have suggested. It could also interfere with the cyanotype exposure possibly. Nevertheless I should give it a try.

Thanks.

 

[Debanjan]

I also wanted to update this thread with another discovery related to this process.. I was exposing for approximately 150 - 160% of my Cyanotype exposure timings to get the previous 2 examples I shared here. With normal Cyanotype exposure times, I see that the Copper-Brown dominates the print with virtually no trace of Prussian Blue -- something similar to a Salt Print .. so the toning possibilities are quite a lot with this process but we need proper calibration and some degree of standardisation.

Both the prints are on Canson Montval paper. Size is A4

 

[koraks]

@Debanjan that's interesting; what fascinates me most is the apparently brown hues you're getting with this. I recognize that if you dial back exposure a little, all you get is the copper image without the cyanotype/Prussian Blue part. You'll see this reflected in my examples in post #85. However, in my case, the hues are pink-orange, not brown, and overall density of the copper is much lower than what they look like in your prints. Can you tell us a little more about your process?

 

[Debanjan]

@koraks - I followed the process suggested by the OP. Since both @Raghu Kuvempunagar and I have almost identical UV box set-up, in order to compensate for the lower sensitivity of the brown FAC, I started with 150-160% of the normal Cyanotype timing. The paper was given a mild citric acid bath and wash to get rid of the buffers. However, I wanted to test the outcome with my normal timings and this was the result. I will redo a series of step charts to check this variation since the one I did a couple of days back was not definitive enough ..

 

[Raghu Kuvempunagar]

Nice work @Debanjan! Thanks for sharing.

The brown we see here is indeed a combination of Copper Ferrocyanide and Prussian Blue. The presence of PB can be tested by reducing the print with either Ascorbic Acid or FAC+UV light. You can notice the change in hue after reduction.

 

[Debanjan]

Nice work @Debanjan! Thanks for sharing.

The brown we see here is indeed a combination of Copper Ferrocyanide and Prussian Blue. The presence of PB can be tested by reducing the print with either Ascorbic Acid or FAC+UV light. You can notice the change in hue after reduction.

Let me try out and report the outcomes..

 

[Andrew O'Neill]

One important variable... I went a few days with disastrous results, (uneven blotchy coatings, coatings that took forever to dry, staining, leaching, zero tone) until finally cluing in in to what the problem was. Room RH. I hadn't realised that my dehumidifier was off, allowing the RH to rise to 90 and room temp down to 15C. Once I got the RH down to 60 and room temp up to 20, Bob's your uncle.

 

[koraks]

Once I got the RH down to 60 and room temp up to 20, Bob's your uncle.

Funny you should mention that. I now recall that on my first day of testing, I tried exposing humid paper. The results were horrible, indeed - worse than I had been getting otherwise. I touched base with @Raghu Kuvempunagar to check how he dried his sensitized paper and he said he blasts them dry with a hairdyer at high heat - exactly what I normally do, too. So I went back to doing that and proceeded with other aspects of problem solving. At least I can confirm that drying the sensitized paper thoroughly doesn't hurt and probably helps along as well. The print-out image is different (stronger) when exposing humid paper.