In Camera Cyanotype, another try

I know it has been discussed here in the past, but I gave it a go with my previously posted 2 bath Cyanotype.
After some initial tests in the dark rainy weather, where I thought, no hope, I got a relative good result.
Today with some sun, I tried again.

Here my joy to see after 1 hour with the 2.8 35mm camera a perfect exposure. To be honest I would have thought the world in UV light would look much different but seems pretty much as in black and white.

Paper : Canon Inktjet 10x15 cm sheets ( I think this is essential)
Emulsion : 10ml Dest water + 2 gr FAC + 1 gr Tartaric acid.

Exposure 1 hour in moderate sun ie there were some clouds every now and then.

developer : 20ml tap water, some K-Ferri + Tartaric acid. (about 2 gr each)

after developing rinse as normal. The color will stay a bit cyan blue, even afer a few days. So I think that is inherent to the Canon Paper.
with that paper no emulsion will come off, I brushed on the developer in these cases.

below my quick edit on the phone
1 the world as we know
2 positive edit in phone of the Cyanotype from the 35mm camera
3 the Cyanotype negative.



Cheers Jan.

Jan de Jong said:

Paper : Canon Inktjet 10x15 cm sheets ( I think this is essential)

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Important correction - Paper : Epson Premium Glossy Photo Paper 10x15 sheets 40 sheets in pack.

high res scan of the 35mm Camera at F 2.8 during 1 hour
high res scan of the box Camera 6x9 during 2 hours f 10 ?
I think it is simple to reproduce if you like.

I am trying to further improve the speed with some other additives.

according to copilots calculation

normal Cyanotype speed : standard cyanotype process (ISO ~0.003),
this way the speed is ISO to approximately 0.09 which is 15 to 30 times faster.
(please let me know if you agree )

cheers Jan.

Let me continue talking about this a bit more

- After exposure virtually nothing is visible, only when the sun has hit it direct for some time there is a slight darkening.
- When applying the developer the print is instantly visible. (could be a nice direct ready negative process by extracting through a small device with a sponge with developer.
- the curve seems relative linear, from the low to highlights. Which surprises because for normal cyanotype we have a very steep curve, here with this slow exposure it seems to behave much better.

- how to increase sensitivity further, I am thinking of adding some tiny bit of Ascorbic acid. (my first test to add this in good quantity immediately oxidized the emulsion to brown rust)
- changing ratio of FAC and Tartaric acid, I have tried 2:1 and 1:1 where 1:1 seemed more sensitive.
- adding something to the developer
- adding food colorant - which color to start, yellow, green, blue, red ? - would that be able to increase the sensitivity range?
- adding chlorophyll to the emulsion? (I would like it to stay relative simple chemical wise)

Some observations is current process already having extended range of sensitivity?
- I made a small test yesterday, with some items, Slate, terracotta, Orange, Banana. grass , twigs.
All items look to have similar gray color as expected, except the Oranges they were the darkest black ie seem to absorb all UV


I find it nice working with this paper,you have to take care to work in dim light as it will expose when in light, but it allows handling like lumen photos but then develop to the examples i have shown.

Hope to hear some feedback, if not I will continue with the above ideas.

cheers Jan.

Yellow food dye has been used to extend the sensitivity of silver based emulsions -- that was what converted 1870s blue-sensitive dry plates to 1900s orthochromatic dry plates. I don't know any reason it wouldn't work for cyanotype, since the mechanism appears to be that the dye absorbs visible blue and green light and transfers that energy to the UV-sensitive material. Whether that's silver specific, I can't say, but it seems cheap to try. Amounts would be pretty small, as I understand it.

Donald Qualls said:

Yellow food dye has been used to extend the sensitivity of silver based emulsions -- that was what converted 1870s blue-sensitive dry plates to 1900s orthochromatic dry plates. I don't know any reason it wouldn't work for cyanotype, since the mechanism appears to be that the dye absorbs visible blue and green light and transfers that energy to the UV-sensitive material. Whether that's silver specific, I can't say, but it seems cheap to try. Amounts would be pretty small, as I understand it.

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Eosine is a specific compound used for this application.

I've no direct experience with either eosine or yellow food dye so I can't help with the specifics. I would check the homemade silver emulsion literature for details.

As for the question about these compounds working with iron-based processes, one will have to do the experiment.

Generally, the 'output' of energy from the doner (the dye in this case) has to 'match' the energy needed by the 'recipient' (silver, or in the case of cyanotype, iron) in order to get a reaction. Thus, the question becomes is iron a close enough 'match' for a system optimized for silver.

Hopefully this is useful even if it is a bit vague. One needs to take a deep dive into physical chemistry to go much further.

fgorga said:

As for the question about these compounds working with iron-based processes, one will have to do the experiment.

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Thank you, I will do some further experiments later this week mixing some more variants, first to see what is optimizing the speed and second in applying some dyes.
I have to make sure they do not interact immediately.

Looking to my photos so far it looks already to have a wider spectral sensitivity as expected. Don't know if you notice that also.
- Green looks a lot darker - Expected
- Red does look the same grey value. Expected was black
- The banana on another picture looks bright - expected was also darker
- Orange - Mandarin - looks very dark.

sorry bit bad picture tripod not very stable and I did not cover the camera so the plate got to hot inside.
top part is the Cyanotype UV and Botom is phone picture
exposure 2 hours at f 4.5

Dynamic range seems to be much better than expected from the cyano process in this way also.
I will send an update once I have it.

cheers
Jan.

UV reflectivity doesn't necessarily have much correlation with visible color. Ever seen "how bees see flowers" photos? What we see as a fairly plain, one-color bloom has high contrast patterns in the range of UV bees can see. Same may be true for cyanotype-derived processes like yours. You'd need to have a UV-filtered digital image to compare for any test of your sensitivity range.

Donald Qualls said:

UV reflectivity doesn't necessarily have much correlation with visible color. Ever seen "how bees see flowers" photos? What we see as a fairly plain, one-color bloom has high contrast patterns in the range of UV bees can see. Same may be true for cyanotype-derived processes like yours. You'd need to have a UV-filtered digital image to compare for any test of your sensitivity range.

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Yes pretty sure now that I only capture UV light since I tried also a 4 hour exposure with the Lomo Sprocket Rocket and that yielded almost no exposure. They probably use a polycarbonate lens which most likely blocks all UV.
Which in it self will be a good camera then to test to see if any of my emulsion experiments have spectrum extension when applying any dyes to the emulsion.

will do the experiments most likely on Friday.

Jan de Jong said:

[Lomo Sprocket Rocket] will be a good camera then to test to see if any of my emulsion experiments have spectrum extension when applying any dyes to the emulsion.

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Seems like a good control -- do you get anything at all from a camera that gave nothing with standard coating? This is real science...

Donald Qualls said:

Seems like a good control -- do you get anything at all from a camera that gave nothing with standard coating? This is real science...

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Not exactly sure what you ask but:

With this coating and paper I mention in the first post, I get results on all cameras, best of course with the f 2.8 there it takes about 1 hour.
but also with the voigtlander 9x12 cm at f 4.5 in the 2 hours exposure. That was the photo with the banana.
the other cameras I tried were 2 box cameras Agfa Synchro at widest aperture which should be f 12. That requires at least 2 hours.
The Dacora is the one with f 2.8 which gives good result in 1 hour.

I had tried before with the Voigtlander with normal cyanotype emulsion on normal paper f 4.5 at 4 hours and got only a faint image which washed off.
The Sprocket Rocket with f 10.8 after 4 hours only very faint image so that seems to block most UV due to the plastic lens.

If I don't manage to improve it further it is in any case already a nice process to make paper negatives in old cameras.

Jan de Jong said:

Yes pretty sure now that I only capture UV light since I tried also a 4 hour exposure with the Lomo Sprocket Rocket and that yielded almost no exposure. They probably use a polycarbonate lens which most likely blocks all UV.
Which in it self will be a good camera then to test to see if any of my emulsion experiments have spectrum extension when applying any dyes to the emulsion.

will do the experiments most likely on Friday.

Click to expand...

Pure polycarbonate doesn't block a great deal of UV, but polycarbonate is usually doped with an additive to block UV, Whilst it is possible to get undoped sheet polycarbonate it requires a special order for sheet materials & is only available from a much smaller range of suppliers. I'm not sure if the same applied to polycarbonate for lens making.

In any case it should be easy to use a UV filter to block UV & so see what your visual sensitivity is like.