A blended ferrocyanide print process

@Raghu Kuvempunagar thank you for linking the video here! I should have done the same.

@Raghu Kuvempunagar is there a way to control contrast with the Ferroblend process? What happens if instead of using a 1+1 mixture of A and B solutions, one uses a 1+2, or 1+0.5?

Hi Andrew,

Contrast control, colour blending and cleaner highlights are intricately linked to the underlying mechanism that produces Prussian White under UV light. I'll have more to say on this sometime soon in a longer post. In the meanwhile, I am happy to share a formulation that produces clean highlights, more subtle colour blending and also importantly, works with Classic Cyanotype sensitiser.

Sensitiser:

(To coat 1 x A4 size sheet)
Water: 2 ml
FAC: 0.25 g
Potassium Ferricyanide: 0.1 g
Ammonium Dichromate 4%: 2 drops

In terms of Part A and Part B described in OP, this corresponds to 1+0.5:
Part A: 1 ml
Part B: 0.5 ml
Water to make: 2 ml

Please note that this sensitiser is the same as the very familiar Classic Cyanotype sensitiser with a few drops of Ammonium Dichromate added. Despite this change, please use negatives of the same/similar density range as before and I'll explain why in my detailed post. If your Part A has Ammonium Chloride in it, result will be warmer.

Developer:

(To develop 1 x A4 size sheet)
Water: 5 ml
Copper Sulphate: 0.1 g
Trisodium Citrate: 0.4 g
Potassium Ferricyanide: 0.1 g

Please note that the developer has Ferricyanide in it. Again, I'll have more to say on the role of Ferricyanide in my detailed post. Order of mixing is critical and Ferricyanide must be added only after a dark green/blue solution is formed.

Will post some examples later.

@Raghu Kuvempunagar very interesting. Looking forward to seeing your examples. So, this method increases contrast?

Many years since I was on any forum, but I have to say, this is a wonderful process.

My first ferroblend print on Canson Montval. neg is 5x7 delta100 in D23.

mdm said:

Many years since I was on any forum, but I have to say, this is a wonderful process.

My first ferroblend print on Canson Montval. neg is 5x7 delta100 in D23.

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Welcome back and thanks for sharing your work. I like the split tone effect here.

Andrew O'Neill said:

@Raghu Kuvempunagar very interesting. Looking forward to seeing your examples. So, this method increases contrast?

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@Andrew O'Neill: I posted a recent print here.

With Dichromate added [edit: to the senistiser], it should be possible to print negatives with density range 1.5-1.8. Please give it a try but don't add Ammonium Chloride.

Raghu Kuvempunagar said:

@Andrew O'Neill: I posted a recent print here.

With Dichromate added, it should be possible to print negatives with density range 1.5-1.8. Please give it a try but don't add Ammonium Chloride.

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With the dichromate added to the sensitiser? Thanks! I'll give it a go.

Andrew O'Neill said:

With the dichromate added to the sensitiser? Thanks!

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Yes, to the sensitiser.

No idea if adding Dichromate to the developer works similarly. I haven't tested.

Usual substitutes for Dichromate like Peroxide/Persulphate/Chlorate might work as an additive to the sensitiser, but I haven't had a chance to try.

@Raghu Kuvempunagar

When you say:
"Please note that this sensitiser is the same as the very familiar Classic Cyanotype sensitiser with a few drops of Ammonium Dichromate added. Despite this change, please use negatives of the same/similar density range as before..."

Do you mean to use negatives for the traditional Cyanotype? Thanks!

Andrew O'Neill said:

@Raghu Kuvempunagar

Do you mean to use negatives for the traditional Cyanotype? Thanks!

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A negative with density range ~1.8 will work best, but ~1.5 might also work. This is, of course, with the addition of Dichromate to the sensitiser.