How would (or wouldn't) IPA affect undeveloped film?

GLS

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koraks said:
That is to say, I'm not sure there really is a mechanism that will make the small percentage of alcohol drive off the remaining water.
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Actually there is: the two form a positive azeotropic mixture, consisting of about 88% water and 12% IPA, with a boiling point lower than either component (around 80 C in this case). This is a well known phenomenon with many binary and ternary mixtures.
 
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koraks

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Ah, thanks, I discounted azeotropes because I didn't realize that an IPA azeotrope would be so much more watery (and therefore more sensible in this application) than an ethanol azetrope. So it would make sense to make a 12% IPA mixture as it should dry a little faster than plain water, or even plain IPA.
 

Ivo Stunga

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What? Is this some kind of stoichiometric ratio kind of black magic? Must try then.
 

koraks

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It won't speed things up beyond what you've got now, though. It'll achieve pretty much the same, but you'll save some IPA because you need only 12% instead of the 20% you're currently using.
 

MattKing

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koraks said:
Rinsing the film in 80% or so IPA would probably be more effective, but I'd consider it a bit wasteful and rather odorous.
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This is what newspaper photographers on deadline would do back when they worked with black and white film.
Of course, that time overlapped with the days when newspaper photographers smoked in the darkroom - what could go wrong?
 

koraks

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MattKing said:
what could go wrong
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Isn't it nice though if you don't even have to drive out to a crime scene to shoot the pictures and can just grab a camera and sell the images of a raging fire at your newspaper's offices to the competitor that hasn't burned down last night?
 

Ivo Stunga

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No, it's water-soluble stuff.

First comes off black in about 30s, followed by light blue in which disappears in about 2 minutes or so. I strive to remove just the black layer just before the blue starts to be affected - with IPA it's doable just fine as those layers don't dissolve in alcohol, stopping the removal process instantly. Blue could be something else, like sensitization dye - I don't know that, so I leave it on film : D

Reading description:
- Aviphot 80 data sheet doesn't mention layers
- Adox HR-50 that uses Aviphot 80 for the basis of it, says this: Anti Halation: Combined AHU/NC

AHU=AntiHalationUnderlayer
NC=No Curling
AH=AntiHalation
 
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