New Cyanotype sensitizer dry times - how long is too long?

Hey all--

I've been making New Cyanotypes using Mike Ware's sensitizer formula for a while now. I'm using HPR and currently not toning at all. I've had good luck with brushing on sensitizer and letting it dry for an hour in darkness before placing in the contact printing frame and exposing in the UV box.

To this point, I've been using inkjet negatives on Pictorico. I have several that are dialed in really well for Kallitype printing, and I spent a long time futzing around with various ratios of sensitizer/citric acid solution/Tween 20 to try and get good tonal range from the same negatives instead of developing a new tone curve for the process.

Long story short, I'll be heading up to my dad's house this weekend (where the P800 lives) and trying to iterate on a new tone curve. For the sake of time, it would be ideal if I could bring with me 10 or 15 sheets of sensitized paper in a paper safe so I don't have to coat and dry while I'm up there.

Any disadvantage to letting the paper sit in a safe for 3-5 hours instead of using it immediately after 1?

It'll be fine, as long as it is kept in the dark.

BHuij said:

letting it dry for an hour in darkness

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I admire your patience. I always blast the paper with a hairdryer on high heat so it dries in a minute, maybe two. Then print right away - although it can also be cut into strips for step tests.
Pre-sensitizing might work, but if there's (chemical) fog, you may end up with a curve that doesn't work well for freshly sensitized paper. If your paper is perfectly stable, however, it shouldn't matter (humidity might still be a factor).

I've always been worried about heat damaging something - Mike Ware says in his article that it shouldn't matter, but I didn't get into cyanotype until I had gotten good results with Kallitype, and I think I remember reading somewhere that Kallitype sensitizer should dry at room temp. Maybe I'm misremembering there as well.

But yeah, the plan is to sensitize several sheets of 8x10 paper, stick in the paper safe, and then cut off strips as needed to test new curves as the printer spits out step wedges.

Hopefully they'll last okay for a few hours in the dark. Humidity shouldn't be a big problem; we have desert air here. In the past, even sensitized paper that had gone from perfectly "lemon yellow" to having a tinge of green at the edges of the painted-on area has always produced good results and cleared just fine.

Here's hoping I don't have any issues. Thanks all!

BHuij said:

Hey all--

I've been making New Cyanotypes using Mike Ware's sensitizer formula for a while now. I'm using HPR and currently not toning at all. I've had good luck with brushing on sensitizer and letting it dry for an hour in darkness before placing in the contact printing frame and exposing in the UV box.

Click to expand...

I presume from what you say that the tíme, say 5 mins or so, needed to apply the sensitiser is OK if done under low tungsten light( max wattage of said light being what?) but it is not OK to allow it to dry under that same low tungsten light?

Is this correct?

Thanks

pentaxuser

I sensitize under a yellow bug light actually. Haven't done much testing of how much time the sensitized paper can handle under low tungsten light because I haven't needed to. But I do put it in the first 3% citric acid bath (after UV exposure is finished) under a low tungsten light for a minute or so, and then do all the washing (~20 mins) under a low tungsten light as well, and haven't noticed any issues.

Never used "New" cyanotype, but the classic formula will last a long time after coating if you acidify the paper first. Varies with the paper though. I've never put a timer on it but I've used paper weeks later.

I did a few preliminary experiments last night using HPR and my existing sensitizer, which is about 1.5 years old (but has been stored in a cool, dry, dark place in a brown glass bottle).

Coated one sheet of 8x10 using Mike Ware's suggested 1.5-2ml for an 8x10, with his suggested 1 drop of 20% Tween 20 per ml of sensitizer. So 40 drops of sensitizer and 2 drops of emulsifier for an 8x10.
Coated another sheet of 8x10 with a significant excess of sensitizer (60 drops or 3 ml), with the same ratio of emulsifier (3 drops).

Dried both in darkness, both came out looking fairly green.

I did a simultaneous test strip in 2-minute exposure increments to try and find minimum time to dmax, and see if the dmax of the "excess" sheet was any better than the "normal" sheet.

Unfortunately, Dmax looked really light for both of the strips. Nowhere near the deep, rich blue I expected (and that I've seen from this batch of sensitizer in the past).

I took the remaining paper with excess sensitizer and just exposed it for 15 minutes under the UV lights, significantly longer than my previously calibrated ~10 min exposure time. It also came out really disappointingly light.

Figuring there wasn't much information left to be gained by exposing the last piece of "normally sensitized" paper, I just tossed it in the acid bath unexposed, to see if I could at least get a paper base white. No dice, I had some blue in there when it was done clearing.

I think this batch of sensitizer is shot. Not sure how, whether it's contamination or age or something else. But it's clear that I need to make up a fresh batch of good sensitizer before I continue any experiments here.

Anyone have a paper they like better than HPR for new cyanotypes specifically? Preferably one that doesn't need to be acidified or otherwise messed with before use? The Buxton paper Mike Ware developed with Ruscombe Mill is pretty much always out of stock.

I've never had a good cyanotype using the Ware formula on HPR.