I think John's idea of exposing it wet an extremely good one and it could bring the needed exposure down into "few hours" range, or even less than that!
For a completely different process, I tried making in-camera exposures of just the FAC mixed w/ a just a little gelatin ( and possibly a touch of CA to get the pH down to where FAC is most light-sensitive, I can't remember now ). I remember the weather was warm, it was probably Summer, and I tried exposures of around 6 to 8 hours in a 5x7 camera in full sun with an un-coated lens at F-2ish. After a few tries I gave up and decided to order some FAO to mix in ( Sandy King found a mixture of FAC and FAO to be a little faster in his "backward exposed" ferric gelatin prints ). Never got back to it, but I remember thinking the exposures were taking so long that I was running into trouble with the air oxidizing the ferrous back to ferric, so I was fighting a losing battle. I have no idea if this would happen with cyanotype ( reverting to ferric ) but it sounds like it's less of a problem since people have managed to make multi-hour/day exposures.
Either way, it might help to place the damp cyanotype paper between two thin sheets of glass in order to keep it damp and exclude oxygen. I've definitely seen with my own eyes that if you put something wet onto cyanotype paper, or if there are areas that are still slightly damp from coating, the exposure is very fast.
And, thank you very much for posting this. The FAO is here and I never continued the experiments... and that would make a great project for this summer. Also now you've got me thinking.... once the gelatin dries, it becomes insoluble, so it might be possible to speed up the process I was working on by dampening the paper underneath it and exposing between two sheets of glass... that's actually a fantastic idea. ( my goal was an in-camera positive process not using dichromate.. I was able to make positive contact prints in full sun with it, but it was too slow for in-camera )
I must be channeling in my inner Ron Mowerybecause I was thinking about how he would say the ISO and characteristics of silver gelatin emulsion changed depending on if it was exposed wet or dry. I hope the pre-coated paper the OP is using can be manipulated theirs obviously has a preservative so it has a shelf-life. I wonder how the preservatives might impact further manipulation ( dampening, steaming, warming, coating with other benign cabinet found products &c ) to boost its sensitivity contrast &c Couldn't find a MSDS on their website..
if there is a kitchen sink chemical ( like vinegar or Vit c or lemon juice or ... ?)
After reading this thread and some others, I decided to take a stab at it. I've been using Sun Art paper for years (mostly for hand and leaf prints), and only recently thought about placing it in a camera. I'm happy to report that I've had some limited success with it today. I took my grandfather's dusty Yashica A off the bookshelf and loaded it with a cut piece of Sun Art paper to try a 4 minute exposure indoors. No luck. I could immediately tell it was pretty far underexposed. I took it outside and did an exposure at 17 minutes and 30 seconds. It worked! I then tried a 23 minute exposure that also worked pretty well. The taking lens on this camera is a f/3.5 Yashimar 80mm, which I had wide open. It was difficult to dial in a "perfect " exposure time, due to periods of intermittent clouds in central New York today.
In-camera cyanotype (Sun Art Paper), Yashica-A, wide open, 9 hour exposure, partly cloudy day. View attachment 323226
This is great! Thanks for sharing.
How come this took 9 hours, versus your previous experiments that took less than an hour each to give results?
Was it different paper, or camera, or sun conditions?
I'd love to be able to make a table of times based on types of paper and aperture, if you're down to help and share some of your data
I think I need a lot more UV light than I have right now, even using New Cyanotype.
Maybe you should offer tanning bed portraits?
Paint bucket pinhole camera. In-camera cyanotype. ~1 month exposure.View attachment 353513
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