Cyanotype development - more sensitive method

nmp said:

You could also try rod-coating instead of brushing, might be even less disruptive. It is what I do in cuprotypes with a 20% ferricyanide solution.

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Niranjan,

My impression so far is that there may be a "craftsmanship" aspect to this process, and it will take some practice to develop the cyanotype without smearing ( different from "bleeding" that happens by diffusion with many iron-based processes if you increase concentrations too much ). When you use your rod for cuprotypes, you do it in a single pass of the rod, is that correct?

-Ned

NedL said:

Niranjan,

My impression so far is that there may be a "craftsmanship" aspect to this process, and it will take some practice to develop the cyanotype without smearing ( different from "bleeding" that happens by diffusion with many iron-based processes if you increase concentrations too much ). When you use your rod for cuprotypes, you do it in a single pass of the rod, is that correct?

-Ned

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Some more background on how I do might be in order to add to my earlier statement.

What I do is what I would call a "touchless" rod coating. I have two shims on either sides of the paper on which the rod glides. The shims are higher than the top of the paper by a certain amount, forming a gap between the rod and the paper. So the rod never presses on the paper, which is held on top side with a clip (of a standard clip-board.) Then I go up and down every minute to make sure there are no dry pockets - 5 passes for 5 minute toning, for example. More liquid can be replenished at either end. The rod never needs to be lifted up as the liquid stays under it at all times with surface tebsion and follows the rod.

Other details:

a) the rod is 12" without any handle - so longer than the width of the paper leaving plenty of room to grab it at both ends

b) liquid is applied to the top edge of the paper with a dropper and then the rod is placed over it so it gets distributed along the whole width of the paper, but does not go over/under it because of the meniscous, unless too much of it is used.

As I mentioned elsewhere, for cuprotype, there is no problem of smearing as such since the receiving compound is not water soluble so it is not going to start mingling with the toning liquid - unlike ferrous ammonium citrate. So this whole gizmo may not be that necessary to achieve the objective - brush coating works equally well and there too I would go over it every miute or so. It so happens that I do all my rod-coating this way, it gives me better control and consistency.

I wonder one of the the reasons King used FO instead of FAC for his cyano Rex process is the fact that ferrous oxalate is also insoluble so stays put on the paper during development.

:Niranjan

nmp said:

Some more background on how I do might be in order to add to my earlier statement.....

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Niranjan, Thank you for taking the time to write that out, I really appreciate it! Even if I don't end up needing that approach for these "developed out" cyanotypes, I'm going to set myself up with a "touchless" puddle-pusher. I just got back from a long walk after reading your post and the whole time I was thinking about my struggles with arrowroot sizing and how this might solve it. I never did get arrowroot-sized salt prints working to my satisfaction, and they have so much potential....
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Too many thoughts to write them all out now, but I may be getting close to solving the "smearing" problem a couple other ways. I'll know better after a few more tests, but I've got a pile of test prints here with varying amounts of FAC and FAO, and if you stack them up by increasing FAC concentration, they also have increasing "smearing" in the highlights. The best one is 5 parts FAO and 1 part FAC... and it's also got the deepest darkest blue and nicest contrast. I've done a few tests with pure AFO, but not a test print yet ( that's the next one! ). Could be that the problem will disappear. I'm following another lead too, but it's too soon to say anything about it yet...

I was thinking about this two ways:

1) I was imagining it's partly mechanical.. the AFO solution is thinner and sinks into the paper more.

2) "Turnbull's Blue" might not be technically different from "Prussian Blue" but they have different colors and the blue made from FAC definitely disperses in water more. The more AFO, the less the blue tends to move on the surface of the paper. ( Mike Ware mentions this as an advantage of his "new cyanotype". )

Now you've got me thinking about another possibility... maybe the ferrous produced by AFO is less soluble or insoluble. That would also help it stay in place.

I'm having fun making these test prints, my exposure time is down to 70 minutes ( that's less than I use in the sun with traditional cyanotype! ) and nice prints don't seem too far out of reach.... we'll see what happens!

nmp said:

...
I wonder one of the the reasons King used FO instead of FAC for his cyano Rex process is the fact that ferrous oxalate is also insoluble so stays put on the paper during development.

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Confirmed with FAO too, by washing the exposed FAO well in water ( paper became nearly white ) then developing in PF. The image is weak because much of the ferrous oxalate was mechanically washed from the surface, but a blue image appears.

I've gone down a huge rabbit hole. I've got 7 kinds of sulfamic acidified papers drying right now for testing. As I increased the FAO to 100%, I also got fogging ( not just smearing of "soluble" prussian blue, as was happening before with FAC ). This makes sense because the FAO really sinks into the paper. I built a touchless puddle pusher ( thanks! It's going to be useful! ), but it did not solve the original soluble prussian blue problem because it instantly disperses up into the bead that is being pushed along! It's kind of wild: you can see it lifting up off the paper into the liquid.

I'll probably start a new thread if/when I get somewhere better with all of this. Tonight's test is Bienfang 360, which I haven't tried yet.

NedL said:

Confirmed with FAO too, by washing the exposed FAO well in water ( paper became nearly white ) then developing in PF. The image is weak because much of the ferrous oxalate was mechanically washed from the surface, but a blue image appears.

I've gone down a huge rabbit hole. I've got 7 kinds of sulfamic acidified papers drying right now for testing. As I increased the FAO to 100%, I also got fogging ( not just smearing of "soluble" prussian blue, as was happening before with FAC ). This makes sense because the FAO really sinks into the paper. I built a touchless puddle pusher ( thanks! It's going to be useful! ), but it did not solve the original soluble prussian blue problem because it instantly disperses up into the bead that is being pushed along! It's kind of wild: you can see it lifting up off the paper into the liquid.

I'll probably start a new thread if/when I get somewhere better with all of this. Tonight's test is Bienfang 360, which I haven't tried yet.

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Hi, Ned:

Looks like you are having fun.

Another rabbit hole to you can pursue, if you so desire, would be to keep the same paper and change the concentration of the sensitizer - if it is sinking too deep, try boosting the solids in the FAO solution. It will do a couple of things. As you increase the amount, it will sink less so helping the fog problem. Secondly, now since the dried film has greater density per paper area of the FAO, Dmax should go up. You can increase it up to the point when it is nearly at the surface (you will start geting glossy surface on drying taking longer time instead of nice matte in a relatively short amount of time) and then the image will just float away in wash (although not eactly the same way in your deconstructed process.)

:Niranjan.

nmp said:

Looks like you are having fun.

Another rabbit hole ......

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My retirement will never be boring. Definitely having fun!

I already went down that particular rabbit hole, but took a wrong turn. I've tried systematically diluting the FAC or FAO "sensitizer" and also systematically diluting the PF "developer". But I didn't try strengthening the sensitizer! That's a good idea.

I noticed something interesting that happened more with FAC than with FAO: a stronger PF "developer" will make a much darker blue, and you can't achieve the same by using more of a weaker PF solution, even if you wait. My speculation is that when the exposed FAC-coated paper initially gets wet, changes start to occur ( oxidation? ) so the initial concentration of PF matters a lot.

NedL said:

My retirement will never be boring. Definitely having fun!

I already went down that particular rabbit hole, but took a wrong turn. I've tried systematically diluting the FAC or FAO "sensitizer" and also systematically diluting the PF "developer". But I didn't try strengthening the sensitizer! That's a good idea.

I noticed something interesting that happened more with FAC than with FAO: a stronger PF "developer" will make a much darker blue, and you can't achieve the same by using more of a weaker PF solution, even if you wait. My speculation is that when the exposed FAC-coated paper initially gets wet, changes start to occur ( oxidation? ) so the initial concentration of PF matters a lot.

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I don't know about oxidation but I would think more in terms of kinetics. Higher PF concentration results in faster conversion to Prussian blue so the ferrous ion does not have to travel far into the developer, increasing the probability that more of it stays on the paper.

nmp said:

I don't know about oxidation but I would think more in terms of kinetics. Higher PF concentration results in faster conversion to Prussian blue so the ferrous ion does not have to travel far into the developer, increasing the probability that more of it stays on the paper.

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That could be it. It's kind of odd and doesn't happen very noticeably with FAO, which can reach a pretty full blue if you pour on 1% PF. Cheers!

NedL said:

That could be it. It's kind of odd and doesn't happen very noticeably with FAO, which can reach a pretty full blue if you pour on 1% PF. Cheers!

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With FAO, you are basically making the New cyanotype in-situ with some of its advantages as enumerated in Cyanomicon. Particularly that, unlike FAC, FAO- based Prussian blue does not suffer from peptization so less of it is lost in the liquid. And as you also observed, FAO sensitizer goes deeper in the paper so it's ferrous ion has greater amount of time available to react before floating away. This makes the process less dependent on diffusion kinetics than the FAC system. How's that for hand-waving!

By the way, do you see any graininess with the FAO print - presumably you are forming potassium ferrio-oxalate when FAO meets PF, just like when one prepares the New cyanotype sensitizer which has to be filterd out. PFO does have a finite solubility, so may be it gets dissolved out in washing.

:Niranjan.

Ha! That's another small mystery. I was expecting to see PFO cystalization graininess in the print or other problems, but so far nothing. I keep expecting "the other shoe to drop" and for this to become a problem as I try different things. In Cyanomicon, Ware mentions using a PF developer as a way around this problem ( in the section on early approaches to cyanotype ), but it didn't make sense to me either how this solves it, since we're still mixing the FAO and PF, and he doesn't explain how/why this solves it. In the section on cyanotype rex, he says the PF developer is wasteful but he wasn't imagining using tiny amounts of it like I am. The prints made from FAO have a somewhat different color than FAC, probably the same as "new cyanotype" vs. "traditional".

NedL said:

Ha! That's another small mystery. I was expecting to see PFO cystalization graininess in the print or other problems, but so far nothing. I keep expecting "the other shoe to drop" and for this to become a problem as I try different things. In Cyanomicon, Ware mentions using a PF developer as a way around this problem ( in the section on early approaches to cyanotype ), but it didn't make sense to me either how this solves it, since we're still mixing the FAO and PF, and he doesn't explain how/why this solves it. In the section on cyanotype rex, he says the PF developer is wasteful but he wasn't imagining using tiny amounts of it like I am. The prints made from FAO have a somewhat different color than FAC, probably the same as "new cyanotype" vs. "traditional".

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Are you familiar with this work?


He had whole bunch of videos on the same/similar approach where he laid out the chemistry behind it but not any more, it seems and the old videos are gone too (or may be I can't find them. May be you can ask him.

:Niranjan