Using Rapid Fixers diluted 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.

<p>

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.

<p>

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.

As far as I can remember the silver is converted to a complex with two

thiosulfat-ions, which is well soluable, unlike the mono-thiosulfat

complex. So a higher concentration would speed up the process, because

it is more likely to find two thiosulfat-ions in a given time.

<p>

I use e.g. Agfa Agefix, which is diluted 1:7 for films as a stock

solution, so test a piece of film with Hypam 1:9 for 2-3 times the

time of 1:4.Any thinner than 1:9? I would be careful.

<p>

With Jobo rotation and Tmax film 1:4 Hypam goes oneway, 120 ml

diluted Fixer per roll, as 10 rolls Tmax per litre is the max. for

Hypam.

Doremus, The only risk to using "almost-used-to-capacity normal-

strength fixer" is that you risk ruining your film due to a

solarization if you open your tank if the film isn't fixed all the way.

Hypo Test in this situation would help to ease your mind. If your fix

is going, fix a long time and hope that it doesn't fail completely.

I've been using a one-shot fixer technique with T-max films for some

years now. Why? Because T-max exhausts fixing baths very quickly, so

it was a question of economy more than anything else.<br>I've found no

drawbacks to using this method, apart from the extended fixing time,

but diluted rapid fixer works in about the same time as a normal

fix.<br>I did a few experiments with offcuts of 35mm, and the film

takes about 4 minutes to clear, so I used the old 'double the clearing

time' rule-of-thumb, and I give T-max 100 10 minutes in a one-shot

fixer.<br>Dilution? Good question. It's got to be routine now, so I

don't even think about it any more. I use 25ml of Ilford rapid

fixer per film, and my single 35mm tank holds 225ml, and the

double35mm/120 tank holds 450 ml, so that's an 8:1 dilution, right?

(Hmm, I had it at the back of my mind that I'd been using 9:1. Ah

well.)<br>The first films I did this way must be 6 or 7 years old now,

and FWIW, they look identical to conventionally fixed ones.<p>Some old

research by Ilford, from their 'manual of photography', says that film

emulsion swells more in low concentration solutions than in higher

ones. This should mean that the dilute fixer is better able to

penetrate the emulsion depth, but probably also means that washing

time should be extended. I've never skimped on wash-time anyway, I

just leave the film washing and wander off to get on with something

else.<br>Good Luck with it Doremus! It does work.