I've started using the potassium iodide test with one shot hypo for film.
I used Rexton Fix-A-Sure. Two drops in 10ml remaind cloudy for a few
minutes. It occured to me that the test solution might be quite strong
and a more sensitive test needed.
I may compound my own solution but would need a starting point. Dan
We do not use this brand in our labs, however, we do use Edwal hypo check. A drop or so in a volume of 32 oz is the usually test ratio as that is the amount usually used. It seems reasonable that 2 drops in only 10ml is very strong. However, i am not a chemical expert. Just can share my day to day experience.
From my researches I have determined that there are three hypo tests.
One is for film and one for each of the baths in a two bath fix process.
Kodak describes the two print tests. I will inquire of group:rec:photo:
darkroom concerning the film test. Dan
In my article on Archival Processing at http://unblinkingeye.com/Articles/Archival...l/archival.html I give the standard Kodak formulas for test solutions. They don't seem to give a means of testing film fixer, so I have always counted rolls or sheets developed and discarded the fixer at some point before exhaustion is supposed to occur.
I always thought the way to test film fixer was time. Take a bit of film and check how long it takes to clear. Compare that with the time you got with the fresh fixer. If the new time is too long dump it. Doesn't help with single use I guess. Unless you set a time you're willing to accept and blend your fixer to that strength. Maybe?-)
Fixer could be old, contaminated, oxidized, or simply full of too much silver. The test I now use for fixer with film is to take fresh fixer, place a dot on exposed film, wait until the dot clears. Then check the clearing time of known fresh fixer: immerse the piece of film in fixer, agitate lightly until the film clears, which is easy to see when comparing it to the cleared dot area. Triple the clearing time is your film fixing time. When the clearing time doubles, it is time for fresh fixer.
The above procedure is recommended by Ilford.
I have timed fresh Ilford Rapid fix and TF-4 to clear film in just under 25 seconds. Fresh sodium thiosulfate should clear film in about two minutes, I believe, but I would like this last point verified by someone who is currently using regular hypo for film.
I use the counting capacity method for fixer with paper.