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If you've used a stop-bath then in general yes the fix time remains effective. In practice with fresh fixer a fibre based print fixes in about 10-15 seconds, and at Ilford's recommended capacity limit 20-30 seconds.
However Ilford do suggest Two-Bath Fixing is highly efficient system, and this is generally considered best practice for archival processing of Fibre based prints anyway.
Ian
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 Originally Posted by Ian Grant  If you've used a stop-bath then in general yes the fix time
remains effective. In practice with fresh fixer a fibre based
print fixes in about 10-15 seconds, and at Ilford's
recommended capacity limit 20-30 seconds.
However Ilford do suggest Two-Bath Fixing is highly efficient
system, and this is generally considered best practice for
archival processing of Fibre based prints anyway. Ian Likely you speak of film strength fix. Those times follow
Ilford's one published time of 60 seconds. That at the fixers
limit of capacity. The chemistries capacity limit at film strength
is way above the archival volumetric limit for dissolved silver.
Four times above to be exact; 2 vs 0.5 grams per liter. For
a Top Notch fix both film and paper strength share the
same 10, 8x10s per liter limit. For best chemical
mileage paper strength is the way to go.
Two bath fixing will deliver 'archival' results at the chemistries
limit rather than the lower volumetric limit. So four times
the capacity and a Top Notch fix. No wonder Ilford
promotes the two bath paper fix. Dan
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From memory Ilford have only added the two bath fixing paragraphs in more recent years, I have the Hypam data-sheet from the early 70's, but it's back in the UK.
G.I.P. Levenson did research on fixers, for Kodak, in the 60's/70's, some of the earlier Kodak work was done by C.E.K.Mees himself. L.F.A. Mason , in Photographic Chemistry states that for films the working level of Silver in fixer shouldn't exceed 15gms/litre and that a level of 8-10gms will have no serious effect, for fibre based papers the level shouldn't exceed 2gm/litre. Those are still the figures Ilford recommend today. (Mason was Head of Reasearch at Ilford, G.I.P. Levenson of Kodak helped with the editing).
Ilford do say "The figures for paper may be exceeded whenever print stability is not critically important." I'd have to say that with RC papers it was very common to exceed these figure with no detrimental effects. Back in the late 70's I shared premises with an advertising/commercial photographer, and many times helped out when he had to produce long print runs. We'd be hand printing many hundreds of prints in an evening and the fixer was heavily used and would have been at the high end of the silver limit, but with RC paper thi cause no short to medium term problems.
The major problem with high silver levels is with archival fixing / washing etc of Fibre based papers, a two bathe Fixing sequence is ideal for maximising fixer usage (economy) while being sound archival practice.
Ian
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Ian and Dan,
Agreed, two-bath fixing is most economical and uses the smallest amount of chemistry for a given capacity. It is interesting that Ilford notes in its data sheet (in a section following the part about capacity) that the limit for not exceeding the 0.5 g/liter silver content in the fixer is only 10 8x10s per liter with their "film-strength" one-minute fix method. This seems rather wasteful to me!
I've been using two-bath fixing at "paper strength" for quite a while now, and don't find the small amount of extra fixing time the least objectionable.
Although my residual silver tests and residual hypo tests have all been good, I was curious about the difference in time between the Ilford and Kodak products due to the relative shortness of the Ilford times, even for the higher dilution. I wanted to be sure that I was not underfixing. As I understand now, the difference in pH plus the addition of hardener in the Kodak product accounts for the need for longer fixing times.
This leads me then to conjecture: Would fixing times for the Kodak product be less if the hardener were not used? And, conversely, if one uses Hypam with hardener, should the fixing times be extended somewhat?
I would love a quick and easy test for the fixer solution itself that was accurate and reliable and that could tell me the dissolved silver content of the solution in the 0.2-4 g/l range. Is there such a test (test strips, etc.)? That would be the best indicator of proper fixing and more reliable than testing the washed and dried print for residual silver.
Best,
Doremus Scudder
www.DoremusScudder.com
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Back in the UK I have Merck Silver test papers, I have to admit I rarely use them because I know the 2 bath system I use works well, and the second developer is below the 0.5g Silver level.
The papers are expensive, there's a US company who make one too but it's not as good (can't remember the brand but I have some in the UK) , a tip I learnt at work was cut each strip into three length wise, we used to use a lot.
Back to the Kodak Rapid fixer, if you leave out the hardener then it should give similar times to the Ilford fixers, assuming it's they are same strength, you'd need to check the MSDS's to see the level of Thiosulphate.
Ian
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Originally Posted by Doremus Scudder I would love a quick and easy test for the fixer solution itself
that was accurate and reliable and that could tell me the
dissolved silver content of the solution in the 0.2-4 g/l range.
Is there such a test (test strips, etc.)? That would be the best
indicator of proper fixing and more reliable than testing the
washed and dried print for residual silver.
Best,Doremus Scudder www.DoremusScudder.com A test for residual silver is of course no test of the fixer.
Test strips, to my knowledge, will detect at 0.5 grams
per liter and up.
The silver content of print papers averages about 1.6 grams
per square meter; 20 8x10s. Do the math and you'll find
each 8x10 will deliver 0.08 grams of silver to the fixer.
That's worst case, no image silver. Greatly exposed
paper leaves less silver in the fixer. I know it's
an approximate method but with some
margin I feel safe.
My single, very dilute, one-shot fix operates well within
the 0.5 limit. Dan
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Doremus;
There is no simple quantitative test for fixer exhaustion, the only test is qualitative. By doing it enough times, you can calibrate your eyeball sort of and estimate exhaustion and you can also test with small snips of 35mm film to get a feel for the fixer exhaustion.
A test for retained silver will help you estimate fixer exhaustion, but only if you use the proper wash.
As for hardener, I would say that all other things being equal, a hardener will slow down fix rate in all cases. This is based on years of experimentation. It is generally due to the reduction in swell imparted by the hardener itself more than any other factor when everything else is the same.
As for silver halide in the fix, remember that not all silver halide is in the fix. A fair portion of the silver halide is now silver metal in the image and the halide is in the developer. So, we used figures from 30% - 60% of the silver halide in the product to estimate the amount in the fixer. A snow scene in a print leaves a lot of silver halide in the fixer, but a dark shadowed forest scene leaves much less. We would average the figure due to variation in print content.
PE
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Ilford recommend doubling the fixing and washing times when using a hardener for films, they recommend NOT using a hardener with Ilford papers.
Ian
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Originally Posted by Photo Engineer We would average the figure due to variation in print content.
PE Ilford does use print averaging. The 10, 8x10s per liter, film
or paper strength, was arrived at by way of averaging a mix
of prints. Long print runs of bright sandy duns vs long runs of
deep dark forest may well justify adjusting one's capacity
expectations. Dan
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PE,
I've been using film clip tests to determine fixer exhaustion for my print fixer for some time. I toss bath one when the film clearing time approaches twice that in fresh fix and/or before the recommended capacity is reached. That coupled with two-bath fixing assures adequate fixing. I was just looking for an easy out that maybe I wasn't aware of... It has always seemed to me that a sensitive enough silver ion test for the fixer would be the most accurate method of determining when the solution should be discarded.
It looks like I'll just keep doing what I've been doing. At any rate, after selenium toning, a long hypo clear (sodium sulfite, pinch of metabisulfite and water) and a long wash, my prints pass the residual silver and hypo tests with flying colors.
Thanks to you and all for the informative answers and advice.
Best,
Doremus Scudder
www.DoremusScudder.com
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