The ferroprussiate that stopped turning blue and started turning grey
I've been making cyanotypes for over a decade and this week a sheet of paper that should have been a deep Prussian blue came out of the seawater wash a muddy grey. Same paper, same emulsion, same sun exposure time I've done a hundred times. The only thing I changed was the potassium ferricyanide, new batch from a supplier I hadn't used before.
I keep turning it over in my hands. It looks like a photograph taken on a day when the light gave up. Not ugly, exactly, but wrong in a way I can't quite name, like hearing a familiar voice speak in a key it doesn't belong to.
I've read that old ferricyanide can be the culprit, that it degrades, but this was supposedly fresh. Part of me wonders if I should just chase it down like an engineer, test everything methodically, rule out the variables. The other part of me is almost charmed by it. It's the first time in years the process has surprised me.
Anyone else ever had a chemical that stopped behaving and you had to decide whether to fix it or learn to love what it made?
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The "voice in the wrong key" description is really good, but I think your instinct about the new batch is right. Potassium ferricyanide from an unfamiliar supplier is exactly the kind of thing that does this. Sometimes it's leftover iron in it that settles out into the paper and blocks the tone development. I'd try washing the paper a little longer or in two baths, see if more of the grey lifts.
I know the feeling though, when you've done a thing a hundred times and it quietly betrays you. It's almost worse than a clear failure because you can't point at what went wrong. Let me know what the new supplier says if you ask them, I'm curious whether it's a known issue with their stuff.
Ah sure look, if the old batch brings the blue back, that's your answer, no doubting it. Ten years of the same ritual and the one variable you change is the one that bites you. The ferricyanide from a new supplier, it's like trusting a fella you've never met in a pub to hold your coat. Sometimes it's grand, sometimes you come out and there's a hole where your pockets used to be.
The two-bath wash is worth trying anyway, even if you're sorted now. I've seen printers spend a week chasing a grey that was only ever dirty chemistry sat in the paper. But "the voice in the wrong key", sure I'd hang that on the wall, and I'm not even a photographer. The thing about a wrongness you can't name is it's always worse than a clean failure, because your head keeps circling it. At least a clear disaster tells you where it happened. This one, you were just stood there holding grey paper wondering what you'd done to offend the universe.
Glad the old tin sorted you out anyway. Now you know to keep a stubborn eye on the batch. 🙂
You're not wrong about the dirty chemistry sitting in the paper. I've been so fixed on the batch I nearly forgot the wash can betray you just as easy. I'll give the two-bath a go this weekend, even if only to rule it out properly.
And the coat-line made me laugh. That's exactly what it is. Ten years I've trusted the same hands and one stranger's batch and the pockets come up empty. The old ferricyanide I had tucked away brought the blue back this morning, clean as ever, so I know now. But I'll keep your wash advice close anyway. Good to have the second opinion from someone who's chased the grey before. 🙂
You're right about the leftover iron, I think. I tested it again this morning with the old ferricyanide I had tucked away and the blue came back, clean as ever. Same paper, same sun. So it's the batch. Which is almost a relief, except now I have a kilo of the stuff I can't trust.
I'll try the two-bath wash on the grey one though, see if it lifts anything. Worth a try before I give up on it.
And you're right that the quiet betrayal is worse than a loud failure. At least when something breaks loudly you know where to stand. This one just sat there looking wrong, like it had somewhere else to be.
Thank you for the patience with it. People who haven't done this don't understand how personal a sheet of paper can get.