Using Rapid Fixers diluted as one-shot

Here's a question for the photochemists out there: Is there any reason why rapid fixers (Hypam, Kodak Rapid Fix et al.) cannot be used at higher dilutions for film than the recommended dilution (usually 1:4), and if so, what would be the increase in fixing time, if any? Does using more dilute fixer have an effect on the way film fixes? I would think, that if it works for paper, it should work for film as well.

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My thinking is this: If I can use a higher dilution of fixer for film, making sure I have enough stock solution for the amount of film I am developing, then I can use it one-shot. This is especially useful when developing on the road. I do 4x5 in trays, and could then reduce my developing paraphernalia to three trays and stock solutions of developer and fix. The fixer, used one-shot, could be discarded along with the developer after use. This would be more economical, eliminate having to pack a bottle of working solution fixer, and eliminate problems with shelf life of the working solution (Ilford says 7 days for mixed Hypam), particularly useful for those of us who don't process larger quantities of film at a time.

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My preliminary tests with unexposed Tri-X and BPF-200 film indicate that the clearing time for conventional films is less than one minute. Following my usual rule-of-thumb and fixing for three times the clearing time would result in fixing times quite close, if not identical, to that used for the stronger dilution. How would using fresh, highly diluted fixer compare to fixing in almost-used-to-capacity normal-strength fixer? Any thoughts, ideas for tests etc., would be most welcome.

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Note: I've posted this on the B&W world film and processing forum as well, but I respect the expertise and knowledge here. Sorry about the redundancy.

Not so much an answer per se. My concern would be to

ensure that the unexposed silver is completely fixed

i.e., cleared and made soluble so it can be washed away.

While the clearing time is a good indicator of, you might want to test

for residual silver. Photographers Formulary sells a residual silver

test package for about $6 (and I think The Developing Cookbook has a

formula for one as well). Good luck. DJ

Doremus, Reading your post, the thing that really stuck out was the 7

day "recommended" shelf life of the Hypam working solution. I have to

wonder if it is really going to die after 7 days or if Ilford would

like to sell you more fixer after 7 days....might be true, never

having used Hypam, I really can't say. But I have used Kokak Rapid for

a very long time and in terms of capacity and shelf life it just seems

to go on for ever.

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Hope this helps,

Bruce

Doremus, I too would question the 7 day use of diluted Hypam. I've used this fix for many years which I dil. 1:4 for film and paper (seperate solns. for each). I keep the dil. fix for many months (depending on use) as a one litre working soln. in which I fix a maximum of ten rolls 120 or 40 sheets of 4x5. With regards film fixing times, when fresh 2 min. towards the end 5 min. Paper is much shorter, RC: 45 secs. FB: 1 min. tops. Twenty year old negs.(35mm and 120) and prints still look good to me.

Sorry I couldn't imput to your question on one-shot fix. But hope this may be of some help.

Good luck,

I also question the 7-day shelf life Ilford recommends for Hypam. I

suspect it is for solution in an open tray, which would be more in

line with Kodak's recommendations, not working solutin stored in a

capped bottle. My problem is: with the unreliablility of fixer tests

(even the common tests for residual silver and are not "archivally"

accurate), how can one really judge the activity of fixer? Is

clearing time of fresh fixer a reliable indicator? (If so, Hypam at

paper strength should work just fine!) Or are there some things I'm

not aware of? Regards ;^D)