Why the time differences between Ilford and Kodak rapid fixers?

[Doremus Scudder]

I always assumed that the Ilford and Kodak rapid fixers were similar products. I've noticed recently, however, that there is a rather significant discrepancy in the recommended fixing times for fiber-base papers.

Ilford's recommendation (from the pdf document from the Ilford web site) for "film-strength" rapid fix (1+4) is 1 minute; for "paper strength" (1+9) is 2 minutes. For two-bath fixing they recommend half the respective fixing time in each bath.

Kodak's recommendation for fiber-base papers (from the instruction sheet packed with the product) are longer: 6-10 minutes for single bath at "paper strength" (1+7) and no recommendation for "film strength."

Given that the recommended times for "general purpose films" are almost exactly the same (2-5 minutes for Ilford, 2-4 minutes for Kodak), I would assume that the respective dilutions of the products were similar.

Why, then, does Kodak indicate triple the Ilford recommended time as a minimum for fiber-base paper? Are Ilford times too short? Is Kodak being over-cautious? Are the fixers really different? What gives?

TIA

Doremus Scudder
www.DoremusScudder

 

[Ian Grant]

They are quite different formulae, the Kodak product contains a hardener, and works at pH 4.4 while Hypam/Ilford Rapid Fixer has a pH of 5.4 (working solution).

The hardener & more acidic pH will slow fixation, and also mean longer wash times are needed. Hypam differs very slightly from Ilford Rapid Fixer in it's buffering which allows a hardener to be used if needed, but otherwise they are interchangeable.

Ian

 

[clayne]

Pretty sure the Kodak RF does not include a hardener. Their normal fixer does include a hardener, however.

 

[Ian Grant]

Kodak's MSDS indicates Aluminium Sulphate and Sulphuric acid in Kodak Rapid fixer, they are only used for hardening, and to acidify the Fixer to pH 4.4 which is necessary to keep the Aluminium Sulphate in solution.

Ian

 

[Photo Engineer]

I have tested both Kodak and Ilford papers in Kodak fixers and some of my own formulation. I find that the Kodak papers (now defunct) fix more slowly than the comparable Ilford papers. So, the difference in instructions may also reflect a carryover from this observation. Kodak probably established that data using their own Polycontrast Rapid IV years ago.

However, presence of a hardener will slow fixing and washing. Also, pH would affect fixing slowing it as pH goes down, so this may also be a factor even if hardener is lacking.

PE

 

[Paul Sorensen]

Kodak rapid fixer comes in two parts, one is a hardener. I have always used it without, but it is there for those who want to use it. I am guessing that the MSDS is for the solution as used, so it would include the hardener. You can see this on this page at Freestyle.

 

[clayne]

I stand corrected, then.

 

[Ian Grant]

It's worth noting that in some thread hear on APUG people mention leaving out Part B of Kodak Rapid fixer, this is the Hardener, as it only contains the Sulphuric Acid and Aluminium Sulphate you effectively have a Fixer very similar to Hypam.

One reason many Pyro users want Alkaline fixers may well have do with the Sulphuric acid in Koadak Rapid Fixer.

Paul the MSDS is for Part A, Part B and also the working solution.

Ian

 

[john_s]

During the controversy about Ilford's rapid FB print washing technique, in which fixing is done, I think, with film-strength fixer for a very short time in order to prevent fixer from penetrating the paper base much, it was said by various people that the technique does not work with some brands of paper incl Kodak, because they need longer fixing. I don't have any references, sorry, because I never liked the idea of fast fixing. And I used some non-Ilford papers.

 

[dancqu]

Kodak's recommendation for fiber-base papers (from the instruction
sheet packed with the product) are longer: 6-10 minutes for single
bath at "paper strength" (1+7) and no recommendation
for "film strength."

Doremus Scudder www.DoremusScudder

I think it must have been faster 50 years ago when I switched
to Rapid. Now days I'm back to Slow, in more ways than one.

The one minute fix in film strength is an Ilford invention. That
one minute fix is followed by a 5-10-5 high intensity wash-
hca-wash. The one minute fix and following wash routine
are the quickest way to a well fixed and washed print.
No more than that IMO.

Those times, BTW, do they stand for the last print through
a fixer at it's limits of capacity? Dan

 

[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

 

[dancqu]

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

 

[Ian Grant]

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

 

[Doremus Scudder]

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

 

[Ian Grant]

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

 

[dancqu]

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

 

[Photo Engineer]

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

 

[Ian Grant]

Ilford recommend doubling the fixing and washing times when using a hardener for films, they recommend NOT using a hardener with Ilford papers.

Ian

 

[dancqu]

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

 

[Doremus Scudder]

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

 

[dancqu]

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.
Best, Doremus Scudder www.DoremusScudder.com

I did play some with the FT-1 test. That is the potassium
iodide drop wise titration of used fixer. I found though that
at very low silver levels the end point of the titration was
indeterminate. Very slowly as the test solution was
added drop by drop an almost invisible
precipitate appeared.

I consider the clip test a valid test. Unlike counting the
number of sheets or square footage the clip test is a test
of the fixer. Out of curiosity and additional assurance you
might keep track of the number of 8x10 equivalents put
through a certain volume of fixer. Remember the 0.08
grams of silver per 8x10. That's worse case, no
image silver.

It would be interesting to know how the two
tests compare. Dan

 

[Curt]

If you leave out the hardener, part B, in KRF then what do you have and what will work to perfection in it? I still have my 5 gallon kit, I bought and use TF-4 now and use it for everything, I'd use the Kodak fixer if I had a use for it otherwise it goes to the chemical disposal center in our town.

 

[Photo Engineer]

KRF is just fine without the bottle of hardener added to it.

It is just not a hardening fix.

PE

 

[Curt]

Thanks very much.

 

[Chuck_P]

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.

Since I'm making the move to using fiber paper, I've been searching and trying to review all the various opinions on FB paper fixing and best management practices for archival quality. I have used fiber before but many years ago and admittedly found the fixing process perplexing. I've no notes on how long I fixed, it was probably for that long time that is seen in Kodak's publication. I did use the residual hypo test on print borders at that time, with bathtub washing, and could never really achieve what was needed.

I've been using Kodak's rapid fix part A only for RC at 1+7. I found this old thread, a gem of a thread to me, I think, on the subject, it's helped me understand more. I just would ask a clarifying question as I am going to begin using the two-bath method: At 1+7 with a two-bath system, what should be that small amount of fixing time for each bath that should be used? I understand the minimal fixing time that does the job, then the better for final washing.

I recall also reading in a different but not as old a thread a post from you about getting those AG-Fix test strips for determining the residual silver in the fixer, I ordered some. They indicate there's a comparison patch to compare down to that 0.5 g/L of silver. IIRC, for "optimal" vs. "commercial" archival quality, the fixer should not rise above that 0.5 level...............just wondering how accurate you felt that strip really is in that regard.

Thanks