Fixer Replenisher

[QUOTES=Helen B]
"ISO 18901-2002 defines image stability in terms
of residual silver compounds as well as residual..."

But where are the amounts? It is a method for sample
preparation which is not representative of our methods.

"The reference specimen, for making residual silver
comparisons, "shall be:"

And on and on. I took Lowell's comment as meaning
post wash residual amounts of silver and thiosulfate.
Both have no ISO established values, AFAIK. Dan

dancqu said:

[QUOTES=Helen B]
But where are the amounts? It is a method for sample preparation which is not representative of our methods.

[...]

Both have no ISO established values, AFAIK.

Click to expand...

Why do you assume they don't exist just because you don't see them on APUG? Are we obligated to reprint everything? Are we obligated to tell everything we know?

The actual numbers are tabulated for all sorts of films and papers and also for life expectancy (e.g., medium term, long term, archival). There is no single number that applies to all.

I don't have the latest ISO standard handy at home now, but according to ISO10602-1993, archival quality fine grain films should have residual thiosulfate in quantity of less than 7 mg/sq meter of film. This number is most likely doubled in later revision, based on the studies that took place in 1990s. For prints, the numbers were also in process of being revised in late 1990s. I think it's somewhere between 14 to 20mg/square meter in the latest standard, but I don't have it at home. Helen, do you have the latest ISO handy?

Anyway, my own testing shows that Ilford's rapid washing sequence (using Ilford Rapid fixer and generic sulfite wash aid) and Silvergrain recommended washing sequences, including an adaptation of Ilford sequence (using Clearfix alkaline fixer and Clearwash washing aid) all meet the ISO standard criteria with a good safety factor (i.e., considerably smaller thiosulfate residue than specified by the ISO standard.). My tests were run with fixing baths to which silver bromide was added to simulate the bath that is just exhausted to the level specified by the manufacturers. (Testing washing method with materials fixed in fresh fixer is kinda cheating, if it is for practical processing purposes, for all reasons I discussed above. The test should be measuring the worst case scenario and show that the result meets or exceeds the standard.)

Helen B said:

To me, that suggests that proper fixing, at least to the point where the complexes can be washed out, is essential for meeting the standard.

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And that is also well known as a fact. The relation between fixing time, fixer composition, fixer pH, washing water composition, washing time and residual thiosulfate level was studied very thoroughly and published by Green and Levenson. There are a few other very important researches done on thiosulfate fixers. One series is by Hirsch, Brumpton, Rumens and other folks (including Green and Levenson) at Kodak Harrow lab. Another line of important work was by Sahyun of 3M lab. Another set of studies was by Aelterman and Vanreusel of Agfa-Gevaert at Mortsel R&D lab. These are very important works to understand for people who design fixing baths and make processing recommendations.

Of course, there are more classic and more "emprical" researches done by Crabtree, Russell, Muehler, and those usual guys at old Kodak labs's processing teams. But at that time the chemistry of fixing reactions were not very thoroughly understood. It was Brumpton and Hirsch who proposed what they called B-salt, which may form within the film emulsion layer but it may be difficult to redissolve or wash out without fresh second fixing bath.

dancqu said:

[QUOTES=Helen B]
"ISO 18901-2002 defines image stability in terms
of residual silver compounds as well as residual..."

But where are the amounts? It is a method for sample
preparation which is not representative of our methods.

Click to expand...

The criteria for residual silver and residual thiosuphates are in the standard. Had you read the standard you would have seen them. The methods for determining residual thiosulphate are given in ISO 18917:1999. They are probably not representative of 'our' methods, as you say. However, that doesn't detract from the fact that ISO 18901 does state the criteria.

dancqu said:

And on and on. I took Lowell's comment as meaning
post wash residual amounts of silver and thiosulfate.
Both have no ISO established values, AFAIK. Dan

Click to expand...

Again, if you had read the standard you would have seen the criteria and you wouldn't have made such an erroneous statement.

Ryuji,

From ISO 18901:2002 : The LE-100 value for residual thiosuphate in 'other film' (ie not microfilm or radiographic film) is 0.050 g/m². LE-500, which is only applicable to polyester-based films, requires no more than 0.014 g/m².

As a side issue, ISO 18901 does give recommended values for the maximum silver concentrations for both sodium thiosulphate and ammonium thiosulphate fixing baths. At 0.5% and 0.8% by weight respectively, these are quite high and should be met easily. The residual silver and residual thiosulphate criteria are rather easy to meet as well.

Best,
Helen

Helen B said:

The residual silver and residual thiosulphate criteria are rather easy to meet as well.

Click to expand...

Indeed, especially after they raised the criteria values in the latest revison! 14mg for film is very easy in manual processing. (What was the latest values for baryta and RC prints for LE > 100 or longer?)

As a side issue, ISO 18901 does give recommended values for the maximum silver concentrations for both sodium thiosulphate and ammonium thiosulphate fixing baths. At 0.5% and 0.8% by weight respectively, these are quite high and should be met easily.

Click to expand...

These numbers should be easily met, as the fixing time becomes noticeably longer at room temperature, and a careful darkroom worker would notice that the fixer is getting exhausted. However, in some processing machines, I've seen ammonium thiosulfate baths used to 2% or higher! Very bad idea if archivality is important.

As Helen noted in her post regarding the ANSI standard, these conditions are based on fixation with thiosulfate fixers.

Many fixers used additional fixing agents such as thiocyanate, and post wash solutions contain thiocyanate and sulfite among others.

The ANSI standards and tests are probably not useful under some of these 'alien' conditions.

PE

[QUOTES=Helen B]
"Again, if you had read the standard you would have
seen the criteria and you wouldn't have made such
an erroneous statement."

I can't argue with that. From those portions of the ISO
you did post and my quick read I inferred incorrectly that
it dealt with the specifics of sample preparation.

"As a side issue, ISO 18901 does give recommended
values for the maximum silver concentrations for both
sodium thiosulphate and ammonium thiosulphate fixing
baths. At 0.5% and 0.8% by weight respectively, ..."

I wonder at film's so much greater tolerance of a
fixer's high silver level than paper's. That 0.5% and
0.8% I think must be commercial levels. Dan

hey look, a flame war about fixers! lol

Markok765 said:

hey look, a flame war about fixers! lol

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Well we do seem to have moved a long way from the question posed in the original post and gotten very technical at times.

I need a knowledgeable expert to do the equivalent of the judge's summing up to the 12 good persons and true of the jury, most of whom are not experts in themselves but are people we trust to reach a sensible verdict with impartial guidance.

I'll settle for Henry Fonda (who will volunteer to be him?) to guide us otherwise we'll remain 12 angry or at least confused men.

Great film by the way

pentaxuser

I don't think this thread went into a flame war.

I also have to say that the truth in chemistry is not decided by democracy. There are a lot of people (including some on this thread) who are very good at making them sound authoritatively and sprinkle technical terms but their posts look empty if not full of nonesense to anyone reasonably knowledgeable in photographic chemistry. So be careful about that...

Hardly a flame war. Animation, not animosity.

Ryuji’s mention of democratic chemistry reminded me of this recent article about Wikipedia.

Best,
Helen

Helen B said:

Hardly a flame war. Animation, not animosity.

Ryuji’s mention of democratic chemistry reminded me of this recent article about Wikipedia.

Best,
Helen

Click to expand...

Helen, I agree with your comment. I also believe that finding something on Wikpedia does not automatically make it gospel.

In addition, having someone adding veiled threats about any of the posters in this thread does no service to anyone and a disservice to everyone.

PE

Photo Engineer said:

...I also believe that finding something on Wikpedia does not automatically make it gospel.

Click to expand...

How true. This is how I hold the compass to Wikipedia articles: if it agrees with my opinion, it is automatically 100% gospel. If it disagrees, it is utter balderdash. And poppycock too.

Best,
Helen

Helen;

I've been thinking of this thread overnight and I feel compelled to comment on "chemistry not being a democracy".

Chemistry isn't A + B = C. There is also D, E, F, G and etc forming as in the case of fixation where several complexes of silver and hypo are involved. Add ammonium ion and another party is heard from. Add thiocyanate and again another party adds its $0.02. The ANSI standards will not even consider image stability when anything but hypo is used.

It takes years of practical experience in this, as in politics, to understand the interactions taking place. And, you cannot do it by just reading books or patents. Today's neutral and alkaline fixes are based on work done by myself and others at EK, including Grant Haist, and take in years of work with fixes containing a whole host of ingredients.

Among other things, synergy or superadditivity is not mentioned once in any of the posts on fixers except ones I have made. (Or, ones disparaging my comments.)

It turns out that hypo reacts in a superadditive manner with a number of ingredients just as developing agents do when you use metol and hydroquinone. The easiest example to come to mind is Ammonium ion and Thiosulfate ion. Others such as ammonium, thiosulfate and thiocyanate are used in the Kodak RA C41 Flexicolor rapid fix, which is based on work I did back in the 60s with a whole host of other co-workers.

It is incredible that others have not taken up on this and other fine work in the field of fixation. Fear of thiocyanate is overrated, as it is used today in toothpaste, but many here have rejected it as being too 'toxic'.

Fine, high capacity fixes exist out there for formulation if anyone is willing to try. There are pitfalls as well. Grant and I both know a whole host of compounds to avoid as well as those to use. Some chemistry will poison or slow down a fix, such as potassium ion or iodide ion. However, in minute quantity, iodide will speed up a fix. This is all outlined in our patent. BTW, the build up in iodide is one of the biggest reasons a fix used for film exhausts or slows down (along with the build up in silver).

I have one compound that is superadditive with fixes, but I cannot get it for a reasonable price. It is non-toxic and easy to use, but very expensive. Other chemicals have been added to fixes, but may cause problems in the long run if the formulator does not know the chemistry involved well enough.

Anyhow, fixation chemistry is as rich and complex a field as development chemistry and can be pursued more than it has. To me, fixer replenishment is a bit of a misnomer. Fixes are exhausted more than they are 'changed' whereas developers are more 'changed' than they are exhausted.

PE