Problem with cyanotypes

[Máx Arnold]

Heyo! First of all I want to describe the special variation of cyantoype that I use, so that maybe you can see what might be causing my pigment to completely run off the paper.
I use a cyanotype formula much like the New Cyanotype by Mike Ware, but I also use a different chemical for developing, and I develop differently.
My current formula, which I call 15 1 15 and you're going to see why, is as follows:
(Please pardon my unscientific measures, I don't have any lab equipment but a kitchen scale)
15ml of tap water (Seems to be slightly alkaline, using distilled water doesn't seem to produce any effect)
1 tsp of oxalic acid
15 drops (from a dropper) of cold Ferric Chloride stock solution from the chem store.
Lately I've tried to add household ammonia, but not knowing how much to use I have tried multiple amounts. --Maybe this is the problem. Last time I might have added a lot, like 5ml, But I just don't remember.
The volume I prepare is enough and I usually let it stand around 2 weeks in an amber glass dropper bottle away from sunlight. I have came to realize that the older the solution, the more this happens and the less exposure I have to do to keep my image intact.
My developer solution is 1 tsp of potassium ferrocyanide (notice the change; I'm not using the recommended ferrricianide, but since this gave me satisfactory results, I just don't bother.) into 1L tap water, then I add a good amount of vinegar, because it just wouldn't work otherwise.
I place around 5 to 6 drops of the solution above and I coat the paper using a brush, then I dry it with a hair dryer until bone dry. My base exposure is 30 seconds using sunlight at 6pm, which proves to be crazy short.

The thing is... Once I get my print exposed I take it out of the frame and place it face down on a plate with the ferrocyanide solution. Blue pigment forms, image is developed. Voilá. Once I take it out of the water, what drips from the paper has clear particles of blue pigment, and as I move it to the wash, I place it face down into some plain tap water and aggitate more blue pigment comes off. Then I place it in the wall, which is covered by ceramic tiles, and gently blot it with a piece of kitchen paper, then almost all the blue gets into the paper, and I'm left with nothing.
I thought it was underexposure, so I exposed longer just to discover that exposing longer worsens this phenomena, and when I tried to underexpose enough so that I can keep the image, but the shadows density is just light blue.
Just for the sake of troubleshooting, I use cheap thin poster paper which doesn't make trouble with the ferric chemistry. I'm going to try coating some drawing paper, if it spoils my chemistry I might try acidifying it with oxalic acid, but I can't promise it'll be good. (Arches, Fabriano, or others don't exist here and I haven't been able to find other papers.)
Now that I think about it it might be the ammonia. I'm going to try plain new 15 1 15 without ammonia and I'll post what happens.

 

[Andrew O'Neill]

I've always stuck with the traditional cyanotype. What paper are you using?

 

[Máx Arnold]

I use cheap thin poster paper which doesn't make trouble with the ferric chemistry. I'm going to try coating some drawing paper, if it spoils my chemistry I might try acidifying it with oxalic acid, but I can't promise it'll be good.

This is basically it, the first giving the best reasults.
I just came back from my "darkroom". I tried using the drawing paper, the whole sheet turned rose colored and unusable. I tried acidifying it, I put ½inch of water into my washing tray and adde 2tsp oxalic acid, the paper sizzled for a long time, and bubbles appeared, but not CO2 bubbles, AIR bubbles in the paper fibres. This rendered the paper artistically unusable, but I tried coating anyway and when I applied the 15 1 15 solution it sizzled a lot more.
The poster paper gave good results. After a test print that showed me that 30 seconds was too little exposure, I ran another exposure at 2 minutes, and the shadows ran away from my print. Literally.

 

[Andrew O'Neill]

The paper is most likely the cause of the grief you are experiencing. If you want to use cheap papers, try white butcher's paper in rolls. That is what my students use. Works right off the roll. The only issue is it's quite thin, and wrinkly when it has dried. Or you could spend a couple more bucks and pick up some Stonehenge... it needs to be acidified first. After years of struggling with inferior papers, and acids, I bit the bullet and bought paper meant for alt processes.

 

[nmp]

Hi, Max:

So you are making positive cyanotypes, right?

Regarding your washing off problem, I would surmise that it has more to do with the physical aspect of the situation rather than the chemistry (although the latter can and will change the former.) My poster boards have two different surfaces, one side is glossy that seem to be filled with something, may be talc or chalk to make it white, I am not sure. The other side is rough without any coating. I am assuming that you have a similar type of poster board and you are using the glossy side. There might be some hindrance to absorption on that side so the liquid stays at the surface. In addition you might be drying it too quick with the hair drier before the sensitizer has a chance to sink in to the paper.

In my experiments on the classic cyanotypes, whenever I had problems with the sensitzer not being absorbed adequately at the paper surface, the result has invariably been various degrees of Prussian blue wash-off. (It does not mean the inverse is also true, but it might be a good starting point.)

So in order to make sure the liquid does not all stay on top of the paper, a number of things can be tried:

- use the flip side of the paper (or change the paper altogether if you can)
- use a surfactant like tween-20 that facilitates absorption
- Do not use your hair drier until the glossiness of the liquid is gone from the paper surface, i.e. let it air-dry more
- Is the sensitizer too thick? If so, then adding more water might help, 20 1 15, may be?

I would try and change one parameter at a time so direct comparisons can be made.

Let us know the progress....sounds intriguing if you can make it work.

:Niranjan

 

[Máx Arnold]

Dear Niranjan:
At first I thought that using ferrocyanide might produce a positive rather than a negative. Turns out it doesn't. The result is just a normal Prussian blue negative.
I thought about letting it air dry more, but I fear it a little because oxalate chemistry is much more sensitive to light, and I work in subdued light, and I fear fogging it. I've saved paper in seemingly good conditions and after some hours it got fogged.
I coat my solution in the rough side of the poster paper, the shiny side is coated with plastic and I'm sure the solution won't adhere properly. Surprisingly enough, my brother turned over the print I posted earlier and I could see that the image was intact, inside the paper fibers. So yeah, my blue pigment is running away from the surface of the paper. (Still the density was deplorable... light blue shadows!)
Usually the solution is just too much for the paper and some areas become quite dump and translucent. They take much more blasting with the hairdryer and they are usually much darker in colour, making the lighter part seem like a stain.

try white butcher's paper in rolls

I know the paper you're talking about, Andrew. If I ever get to buy some ham and cheese AND the paper they give me is white, then I might try it. What is difficult is finding the one that's white, not shiny white, not printed on the other side and that stands some water. Not only it is difficult when shopping for a sandwich, but also to find it on paper distributors.

The only issue is it's quite thin, and wrinkly when it has dried.

Oh, no worries. My good ol' poster paper wrinkles when dried and it's also quite thin. I get over this (And achieve a much better looking print) by gluing it to some thicker cardboard afterwards and I hide part of the wrinkles by passing the clothe's iron set to nylon (Or whatever is lower, high temperatures meant for wool or cotton destroy the Prussian blue and might make a cyanide hazard) over it. I have prints that were in terrible condition, highly wrinkled, broken, because of prolonged wash after toning, and using the iron I could make acceptable prints. Maybe your students would like to try it, if they don't do it already. Plus, the iron might give it a mild satin look if you friction it with the surface of the paper when hot, which makes it look somewhat better. Nevertheless, it might be undesirable to some photographers.

Do not use your hair drier until the glossiness of the liquid is gone from the paper surface, i.e. let it air-dry more

I've tried this, and with good results. I know if I want to make a better print there's some tips I have discovered (But haven't put to the test):
- Let it air dry, or at least, let the solution rest some seconds in the paper so to allow it to get into the fibers.
- Better dry with cold air, I assume, since heat might fog the solution. (My hairdrier doesn't have this switch... I could add it, but it's more pain than it's worth)
- Let the dry paper sit in the dark for one minute (I found that more time fogs my paper, but I might be wrong)
These are things that I didn't do today... Maybe they actually help.

Is the sensitizer too thick? If so, then adding more water might help, 20 1 15, may be?

I've doubted of the 15 1 15 proportion. But then I found one of my best prints and it was printed with it, so I don't think it is as bad. What keeps me from diluting it to make 20 1 15 is that this would change the concentration of the ferric chloride and it might impact the darkest achievable blue, but again, I'm not sure. What is to be said is that 15 1 15 is a saturated solution of oxalic acid, and in old solutions crystals form with ease (An interesting thing, Oxalic Acid crystals have parallelogram shape, and this is not what appears in my solutions, it is rather like a prism, and this might be tris-oxalato-ferrate III, the actual photo sensitive salt. Goodness!)

So yeah, I've got work to do on this...
Thank you very much for the help!

 

[nmp]

There is a lot going on here. As they say, there's more to this than meets the eye – as it usually is in all things cyanotype.

Your drying process still seems to me as too aggressive...unless you have a paper which is like a sponge and it sucks up the liquid soon as you apply (which might be happening with the rough side of the poster board without any sizing, I don’t know.) If it goes too far down the fibers, it would create its own problem of lower shadow density or the Dmax. May be that's what you are trying to prevent with quick drying. In absence of that, using heat within seconds would leave a film of the sensitizer on top of the paper with no “anchor” to hold on to when the initial colloidal Prussian blue is formed so it would just float away.

Now that I somewhat understand the positive/negative nature of your process, I think the origin of your fogging, that seems to be the other big problem you are dealing with, might be something other than too long of a dry time. So could be the cause of the apparent wash-off of the blue, in addition to (or absence of) the above physical phenomenon. But before that a couple of questions:

1. You say “...then I add a good amount of vinegar, because it just wouldn't work otherwise.” What happens when you do not use vinegar?

2. Regarding the fogging, what happens if you take a piece of paper immediately after drying without any UV exposure at all and put it in the developer – does it turn blue and does the developer turn blue?

:Niranjan

 

[Máx Arnold]

What happens when you do not use vinegar?

I think I remember the blue is not good enough. It takes time to appear and it is light blue at most. Plus everything would come out of the paper. I've read in internet dozens of times about the blue coming off and they said that acidifying the wash water was a solution, and so my developer is partly my wash, I add vinegar to it. I've had good results with it, so I didn't think I had to change it.

Regarding the fogging, what happens if you take a piece of paper immediately after drying without any UV exposure at all and put it in the developer – does it turn blue and does the developer turn blue?

Well, yes. (Lightly blue, actually. Very light) I think this has to be with the fact that I'm using ferrocyanide. As you see, ferrocyanide is used in conjunction with ferric chloride alone to precipitate Prussian blue. What seems to happen is that after the minimum amount of exposure, if I then dump it in the developer, no blue will get formed. And all the blue that is formed is proportional to exposure. I've been able to get clear highlights without a problem. I've been able to mix 15 1 15 and the developer solution into the same recipient, and some blue gets formed initially, but then it stops. any blue formed afterwards is a product of light exposure.

 

[nmp]

Ok. I am wondering if the acidic developer is encouraging the formation of direct Prussian blue from ferric ions and K Ferro - both in the solution and on paper. That could be the source of the seeming wash-off. Acid is really not required here as like in classic cyanotype where you are actually trying to encourage ferrous/K ferri reaction for maximum blue. Here you want to suppress the positive reaction between ferric and K ferro.

(There is a great explanation of this mechanism in Appendix III.9 in Mike Ware’s Cyanomicon.)

Have you considered adding hydrogen peroxide step here since the main image is initially all formed of Prussian white that would probably take a long while for full blue development.


:Niranjan.


P.S. Have you looked at this video showing a similar process but with FAC instead of the ferrio-oxalate and it looks like he does not use any acid in the developer, just straight K ferro:

 

[Máx Arnold]

Wow... I didn't know what I described earlier was in cyanomicon. I had the book but I never thought it was there.
I made a test today. I sadly overexcited and made two things at once... well... three.
I acidified the drawing paper I told you before, but I instead used dilute hidrochloric acid, which didn't produce any CO2. Nice!
Then I coated with 20 1 15, like you suggested. It sizzled anyway, so I'm going to let the paper sit way longer the next time.
Then I let the paper soak in the emulsion until it stopped looking damp on the reflection. Then I slowly dried with my hairdrier in the slow setting, which was warm but not violent. And I also guarded some distance between it and the paper. Then, when it was mostly dry but still not bone dry, I blasted it with the hairdrier on high.
I exposed 2 minutes, at 6pm. Trying to account for an underexposure I saw at 30 seconds.
Then I dumped it back on my stock solution of ferrocyanide, and I saw blue forming... Some pigment came out, but almost everything remained on the paper, so yeah... It 'worked'
I'm going to attempt it again tomorrow.

The video you show, Niranjan, is quite good. I'm really going to try using a 1% solution of potassium ferrocyanide, without any acid, and I'm going to tell you how it goes.

 

[nmp]

Yeah, everything is there in Cyanomicon....

Actually what you are working on was pretty standard (not the exact formula but the principle) in the second version of blue printing process i.e. blueprint process 2 or the Type B process as described in the Appendix III.8/9 of the book. Even before that, this goes all the way back to Herschel who tried to make a go of it as a positive working process but was not successful due to the dual reactions of both ferric and ferrous going on at the same time (section 4.1.4 of the book.)

Looking forward to seeing more progress, hopefully with some good prints as well. I have been meaning to do this process at some point myself. There are some inherent advantages with this approach in comparison to the classic cyanotype.

:Niranjan.

 

[Máx Arnold]

So today was sunny...
I did make the 1% solution of ferrocyanide, and just as a form of measure, I went for the weight by volume approach, instead of molar mass. Something weird happened.
The 1% w/v Potassium Ferrocyanide solution was colorless, instead of the light yellow liquid I'd be working with normally. I thought it would be great.
I forgot about the other papers for instance, and used my poster paper instead. I used a new negative I got copied yesterday, and I was hoping great results. I coated a very little amount of old 15 1 15 + ammonia, that I had lying around and used to give me good results. I let it soak into the paper fibers and then I slowly dried it with my hairdryer set to low. Once done I placed it in the frame and exposed to the 2pm sun for thirty seconds. Then I came back, and submerged it on the 1% solution described above.
I saw blue. A lot of blue. And some blue came off the print as I took it into the acidic water bath. I washed it and blotted with a piece of absorbent paper. Some more blue came off, but it wasn't alarming. Once I had the print dry I could see I had hideously overexposed my print. I could barely tell the presence of the tree and the slide. (My new negative was a shot of my backyard)
Overexposed...
Indeed it was.

I made another test and this time I got crazy mad at the exposure always seeming to get shorter every time I tried to print. I can't believe that for the last two months I've only got overexposed, blue-leaky, highlight-stained prints. I coated another sheet of paper the same way and this time I exposed for 5 seconds. I can't stress enough the fact that 5 seconds is such a short printing time, even for making cyanotypes this way which has always proven to be much faster, I thought my paper was going to come out white, And it didn't.
The resulting print ended up being the same or slightly more overexposed than the last one, Yet there was a drastic reduction of exposure time! I don't understand this...
The only easily noticeable difference was that the one exposed at 5 seconds had a richer blue than the other one, but that is probably because I might have coated more solution this time.

I think I should just start all over again. New chemistry, new cups, new measuring instruments, new UV light source.
Do you guys think the same?

 

[Máx Arnold]

As they say, there's more to this than meets the eye – as it usually is in all things cyanotype.

there is more blue to this than meets the eyes...

 

[nmp]

I think I should just start all over again. New chemistry, new cups, new measuring instruments, new UV light source.
Do you guys think the same?

You have many moving parts....indoor artificial UV light source is a must for doing any kind of new process development work, I think. I also recommend that before you do an actual image, print a step wedge and work on small size paper on which you can repeat the process conditions more precisely. Otherwise you will go in a circle (something I am much too familiar with.)

:Niranjan.

 

[Máx Arnold]

before you do an actual image, print a step wedge and work on small size paper on which you can repeat the process conditions more precisely.

Yup, you're soooo right. But it's just so difficult... Since I expose in my backyard, and the exposures are so short, I tend to feel like "sunbathing" for thirty seconds at a time. I can't describe how good it feels and how much it makes me distract from the exposure. Plus I count to thirty out loud (Beating at 60 bpm, 1 Hz, one second at a time) since I don't have a timer right now. I'm going to tell you something: This is all wrong. WRONG, WRONG, WRONG.

I shouldn't have let my process get so messy, my place get so clumsy, my attention get so distracted, and then come here and cry out loud "Why are my prints so bad?!". If I want to work with chemicals for the rest of my life I need to grow up to do so consciously and carefully. That's what I'm going to do.

PLUS I discovered that the main reason for all this trouble is that all the prints look overexposed, they all look like I'm cooking them in a solar oven instead of "gently showing them to the sun" like I use to say. The seem like they are, but the effect is different.
Comparing a truly overexposed print, a good print, and my two last tests (At thirty and five seconds, without much difference) I came to discover that it is not that they are hideously overexposed, but that the tonal scale is just gone nuts (I want to swear but... I'm not going to). The shadows are a flat, greyish, mild blue, while the highlights look like they've been severely toasted in a blue hue. This is not because my exposure is too long, nor too short, nor because my developer is not good, nor because I'm fogging the paper unintentionally, but rather because my highlights just aren't clear. I mean, I clearly don't need to shorten exposure, I need to clean my highlights.
I think the main reason is...

I am wondering if the acidic developer is encouraging the formation of direct Prussian blue from ferric ions and K Ferro - both in the solution and on paper. That could be the source of the seeming wash-off.

I think you're right. Prussian Blue is probably getting generated at my highlights without any mercy. The problem I have is... I have no idea why this is so. I would blame the ammonia, but a plain 20 1 15 solution like you suggested proved to work as bad, if anything a little better, than the one with the ammonia in it. Maybe it's not the ammonia, but the fillers and other substances that are indeed present in my bottle of 'household ammonia' (a weird white thing that's in suspension, sulphamic acid and other things people add at the factory so that you don't get too smart at their product and try to make amphetamines or anything stupid)...

It'd be of great help to find the Mike Ware's formulae for the Type B (Or BlueLayer) blueprint process, the only thing google shows me is Slyka's blog (Slyka's Stuff) when trying to make a cyanotype enlarger. Another thing that'd be of great help is finding formulas, or recipes, for the ammonium ferric oxalate sensitizer, since my approach comes from the original proportions made by Arpan Mukherjee and my own intuition.
Here's the link to the Arpan's entry at Alternative Photography: http://www.alternativephotography.com/photography-with-iron-iii-salt/

It has been already of great help the advice and consideration I've received here. That's why I'm here. I'm very thankful.

 

[nmp]

Yup, you're soooo right. But it's just so difficult... Since I expose in my backyard, and the exposures are so short, I tend to feel like "sunbathing" for thirty seconds at a time. I can't describe how good it feels and how much it makes me distract from the exposure. Plus I count to thirty out loud (Beating at 60 bpm, 1 Hz, one second at a time) since I don't have a timer right now. I'm going to tell you something: This is all wrong. WRONG, WRONG, WRONG.

- mobile phones have timers and stopwatches, you don’t have to count 1001, 1002…

- if the exposure times are too short, try putting a translucent film on top of the negative or the glass or make the negative on a such a film. It will give you more time to watch the latent image and decide when to stop.

I shouldn't have let my process get so messy, my place get so clumsy, my attention get so distracted, and then come here and cry out loud "Why are my prints so bad?!". If I want to work with chemicals for the rest of my life I need to grow up to do so consciously and carefully. That's what I'm going to do.

PLUS I discovered that the main reason for all this trouble is that all the prints look overexposed, they all look like I'm cooking them in a solar oven instead of "gently showing them to the sun" like I use to say. The seem like they are, but the effect is different.

- get a gram scale, they are cheap and very helpful when making small quantities. I even weigh my water instead of approximating small volumes (speaking of water, use distilled always – no telling what your municipal water carries. OK for washing but not in sensitizers.)

Comparing a truly overexposed print, a good print, and my two last tests (At thirty and five seconds, without much difference) I came to discover that it is not that they are hideously overexposed, but that the tonal scale is just gone nuts (I want to swear but... I'm not going to). The shadows are a flat, greyish, mild blue, while the highlights look like they've been severely toasted in a blue hue. This is not because my exposure is too long, nor too short, nor because my developer is not good, nor because I'm fogging the paper unintentionally, but rather because my highlights just aren't clear. I mean, I clearly don't need to shorten exposure, I need to clean my highlights.
I think the main reason is...

I think you're right. Prussian Blue is probably getting generated at my highlights without any mercy. The problem I have is... I have no idea why this is so. I would blame the ammonia, but a plain 20 1 15 solution like you suggested proved to work as bad, if anything a little better, than the one with the ammonia in it. Maybe it's not the ammonia, but the fillers and other substances that are indeed present in my bottle of 'household ammonia' (a weird white thing that's in suspension, sulphamic acid and other things people add at the factory so that you don't get too smart at their product and try to make amphetamines or anything stupid)...

- Ammonia is a pain. I hate to deal with it (that and vinegar.) You can substitute it with ammonium bicarbonate – also known as Baker’s ammonia that you can buy in a grocery store. Great thing about that is it fizzes as you add to an acidic solution so if you are trying to neutralize, you stop when fizzing stops. And there is no overpowering smell.

It'd be of great help to find the Mike Ware's formulae for the Type B (Or BlueLayer) blueprint process, the only thing google shows me is Slyka's blog (Slyka's Stuff) when trying to make a cyanotype enlarger. Another thing that'd be of great help is finding formulas, or recipes, for the ammonium ferric oxalate sensitizer, since my approach comes from the original proportions made by Arpan Mukherjee and my own intuition.
Here's the link to the Arpan's entry at Alternative Photography: http://www.alternativephotography.com/photography-with-iron-iii-salt/

- You can probably find a lot of patents from that era - 1930’s, 40’s etc. like this one:

https://www.freepatentsonline.com/2350991.html)

But most of them would also incorporate ferricyanide (type AB.) Usually they added both ferri and ferro together in sensitizer - not in the developer. Plus good luck with duplicating anything that the patents say.

- If ferric ammonium oxalate is what you want to use, why not buy it readymade – it is the one of the cheapest one around. Deal with one less headache.

- Important to note that Mukherjee article deals with ferricyanide not ferro – your process may not be comparable to his as far as the outcome regarding the highlights.


Good luck...you have your work cut out for you!

(I suspect that highlight staining was indeed the major obstacle to this process, that's why perhaps it never caught on in comparison to the classic cyanotype using ferricyanide.)

:Niranjan

 

[Máx Arnold]

Goodness...
Niranjan, you've been of great help.

According to the patent you mentioned, the proportion of the chemicals in the sensitzer has to be around 70% Ferric light sensitive compound and 30% iron-cyanide salts, otherwise, the chemistry would bleed. Imagine that, being my 15 1 15 solution quite concentrated, I was using a 1% solution of ferrocyanide... So today I adjusted things:
After some experimentation with the dilution of 15 1 15, I decided to keep my original recipe for the developer bath and go with this formula:
20 1 15 2:
- 20 ml of tap water at room temperature.
- 1 tsp oxalic acid
- 15 drops of cold ferric chloride stock solution
and 2 ml of concentrated household ammonia.
I was blaming the ammonia so terribly... But it actually was the proportion of chemicals that led to this madness. And I tried to reduce the amount of ferrocyanide thinking it would work!
I made some tests and I got clear highlights! Yay!
And then I made a print...
I exposed for longer than I used to, but the exposure was right, a little bit underexposed, since the shadows weren't so deep. (I was using a paper negative)

I feel relieved now that I could solve this problem, but I couldn't have done this without your help, and the help of everyone who replied to my two threads.

Thanks a lot!!

 

[nmp]

Goodness...
Niranjan, you've been of great help.

According to the patent you mentioned, the proportion of the chemicals in the sensitzer has to be around 70% Ferric light sensitive compound and 30% iron-cyanide salts, otherwise, the chemistry would bleed. Imagine that, being my 15 1 15 solution quite concentrated, I was using a 1% solution of ferrocyanide... So today I adjusted things:
After some experimentation with the dilution of 15 1 15, I decided to keep my original recipe for the developer bath and go with this formula:
20 1 15 2:
- 20 ml of tap water at room temperature.
- 1 tsp oxalic acid
- 15 drops of cold ferric chloride stock solution
and 2 ml of concentrated household ammonia.
I was blaming the ammonia so terribly... But it actually was the proportion of chemicals that led to this madness. And I tried to reduce the amount of ferrocyanide thinking it would work!
I made some tests and I got clear highlights! Yay!
And then I made a print...
I exposed for longer than I used to, but the exposure was right, a little bit underexposed, since the shadows weren't so deep. (I was using a paper negative)

I feel relieved now that I could solve this problem, but I couldn't have done this without your help, and the help of everyone who replied to my two threads.

Thanks a lot!!

Wonderful, Max...I am glad it is working out for you. You are welcome, but mostly I am sure it is your perseverance to keep plugging away (that and reading the patent I threw at you) that made the progress happen.

Using a paper negative is a great idea, since this process is so much faster than the classic cyanotype. It will also probably be great for making in-camera negatives themselves if you have a large format camera.

Good stuff....

:Niranjan.

 

[Máx Arnold]

Using a paper negative is a great idea, since this process is so much faster than the classic cyanotype. It will also probably be great for making in-camera negatives themselves if you have a large format camera.

Wow.. this got interesting.

I bought the chemicals for this process because of exactly that reason, making photographs in-camera. (That's exactly why I quoted Arpan Mukherjee, he was 'clicking photographs' with a similar formula)
I used to get promising results, but almost always the paper got some amount of base fog.
Eventually I gave up the thirty minute exposures to be making pinhole photographs in thirty seconds using RC Silver based paper.