Film (and paper) can fog between stop and fix if exposed to light. It is safe to expose the film to light after at least 50% of fixing has occurred. It has happened to me more than once developing paper, never film, I never expose unfixed film to light.
I just perused Kodak Practical Processing in Black and White Photography, (pub#229 -pg 6 under Dev controls-temp of developer-effect on fog) regarding fog . Higher fog is sometimes a result of too high development temperature, and if occurs, reduce temp.
Last edited by Rick A; 06-26-2014 at 10:51 AM. Click to view previous post history.
Reason: removed term dichroic as it was not in text as read
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-it's probably dichroic fog
-it could be due to the high development temp
-it could be caused by accidentally getting some fixer in the developer
-it could have been exhausted fixer
I doubt it is exhausted fixer. When I did 2 bath fixing, I used to run my first bath to utter exhaustion. I think it's most likely due to the high temperature or possibly the bottom-of-the-bottle Rodinal.
Does it meet the criterion of dichroic fog? Greenish by reflected light and red by transmitted light. Simple test.
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Whilst you can never be sure without it in front of you, I have had a look at the enlarged image, it does not look like dichroic fog to me ( at all ) plain and simple unfixed. Re-fix and we will know for sure.
When was the last time you saw dichroic fog on any modern film emulsion ?
And finally basic darkroom, lights do not go on until the fix time is up and NEVER ever
before the film or paper is in the fix.
Simon ILFORD Photo / HARMAN technology Limited :
I already re fixed twice in fresh fixer which I tested to clear film in 30s, in addition to the original fix which was sufficient to fix a roll of tmax which looks fine.
Originally Posted by Simon R Galley
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I saw dichroic fog very recently, with fresh Tri-X, processed in complete darkness and normal temperature, but an experimental developer that was high in solvent. I've also seen underfixed film before, but the images BetterSense posted remind me of my dichroic fog samples. The biggest difference, and what gave it away top me, are the fingerprint patterns on the film, for some reason you get these with dichroic fog but never with underfixed film.
Originally Posted by Simon R Galley
BetterSense, did you just mention two bath fixing with a very exhausted fix 1? That would explain it. Fix 1 became alkaline from carry over, to the point where development could occur. Loaded with Silver, there was plenty available for physical development. I think we have your culprit right there.
If you do this again, use a stop bath and rinse a few times before you fix, this way pH of fixer 1 stays below 6 and no development will occur.
Trying to be the best of whatever I am, even if what I am is no good.
Originally Posted by Rudeofus
The fix I was using was well used but still had enough to fix tmax in a reasonable time I was only using 1 bath. I used to use 2 baths back in the good old days when I had a darkroom, and I would use bath 1 until it didn't work at all, with no problems.
The rodinal I was using was old and had crystals precipitated out. It was still working fine for many rolls that way, but this time I was developing at 25C since I was out of ice.
The fog does look reddish on the light table. Happily I was able to print the images I wanted despite the fog.
In the future I will throw out my Rodinal if it precipitates out slushy crystals, develop at less than 25C, and rinse my film extra well be before the fixer.
Acros is a sigma grain a similar film to Tmax or Delta and needs long fix times and may not fix with exhausted fixer.
Rodinal crud is normal I normally rinse out bottle and pour into dev tank. It is supersaturated normally and can crystallize out no effect on performance ignore.
Id say you have under fixed or exhausted fix or contaminated.
keep a record of number films fixed and mix date
fix by inspection for twice clear time
The delta's are pigs to fix.
How to remove the dichroic fog:
A 5 minutes bath of KMnO4 1:1000 then an enlightening (I don't know the exact term) in hypo 1:10.
Found in a book, never tested.
Have a nice day.