I guess I spoke too soon. The CMC formula is great though. The resolution is basically photographic.
https://lemmy.world/post/26591859
For use on plastics you need the sizing that I proposed on there. For regular paper I just noticed that that you shouldn’t use peroxide to develop anything. First of all there’s actually no hardening due to free radicals necessary. But I noticed that with bad paper, it will immediately turn all blobs of ugly gloppy blue. All that is needed is to remove the yellow sensitizer, so start with water only. But I am thinking that a better developer would be a quick wash in dilute HCl, citric, acetic, oxalic or sulfamic acid.
This is great cheap watercolor paper: https://a.co/d/aNkZqji It works fantastically out of the bag. It comes in a very losely packed thin plastic. Some complain that it comes damaged on the corners but that was not the case for me.
I’ve tried an old batch of nenah 94lb paper? And that worked well with less surface waviness. Photo paper blued badly on peroxide but maybe it will work with dilute acid.
It’s really easy to focus the projector. Just do the same coating on a focusing paper but use fluorescent yellow (biggest response to UV). The paper will glow brightly with the image. You can use clear poly carbonate safety glasses to look at the image while focusing the UV.
With this stuff, what you see is what you get + yellow. So just expose and check a few times to see how the exposure is going. The “new cyanotype” formula does solarize so you’ll want a little solarization. But you can also control the “negative” via GIMP and you can adjust it as you feel it’s good to your look.
One of the interesting parts of the recipe is the Sodium Benzoate. I got the idea to test it for photo initiator, which it seems to do but weakly. Instead, along with the sulfamic acid it seems to harden the CMC in place. When you mix the two things into the CMC, there’s a white precipitate. This makes it almost like a shear thinning white paste that flows very well. Once the New Cyanotype is added, you get a very bright green pasty stuff to coat the paper with. Make sure to not cake it on. It leaves an ugly finish with too much. Also too much sensitizer just makes it longer to wash off. No second coats, that ruins the first coat. That may not apply to a coat that’s already bone dry after development, don’t know.
Here’s what it should look like when the Sodium Benzoate is added after the acid was added.
This is after the sensitizer is mixed in:
Then just wait for it to dry and expose. Here I’m using my eBay DLP projector with a cheap Chinese blue UV filter:
And when the exposure is finished ~15 to 20 minutes, it looks like this:
Then …Here I sprayed peroxide and then tap water wash, but like I said, it should probably be an initial acid bath followed by just tap water:
Here’s the original image from another channel: