Fixer Replenisher

[Markok765]

I bought a 5L bottle of agfa FX-universal fixer(10 dollars, 5 times cheaper than ilford rapid fix) it says for the fix 1-7 and the replenisher 1-6. how would i use the replenisher, how much would i add and how much can i replenish?

I an using 1L of fix at a time.

Do i even need to replenish for the small amout of stuff i do?

It it too much work for a small amount of processing?

 

[David A. Goldfarb]

I wouldn't bother replenishing. Just toss it when it's exhausted.

It makes more sense to replenish if you have a big dip-and-dunk system with over 100 gallons of fixer.

 

[Nick Zentena]

Replenishing isn't very hard. You just pour off some of the old and add some of the new. OTOH for B&W I'd just suggest doing two bath fixing.

 

[fhovie]

I have never cared to do 2 bath fixing - but I don't use Sodium Thiosulfate - I stick to Ammonium Thiosulfate and test it at the end of each session. I can't imagine replenishing Fixer. Fixer is not like developer. Developer, when used, looses developing chemistry to chemical reactions and more developing chemistry must be added. This can go on for a long time for most developers. Fixer is not that way; fixer disolves the silver in the emulsion and the silver goes into suspension in the fixer. When the solution can hold no more silver, the fixer is exhausted. Short of removing the silver, adding more Thiosulfate will not increase the holding capacity of the solution. The fixer I use (TF3) will clear film in 30 seconds. When it clears film in 60 seconds, I chuck it (it will go downhill fast from there) At 45 seconds, I watch it very closely. I choose the fixer I use because it has a ph of 8. My entire process is ph 8 and higher. If I used Sodium Thiosulfate, I would likely use a 2 bath system. My darkroom is pretty tiny. My process works fine.

It is SOOOO embarassing to have a print brown out years later because it was not properly fixed. It is like a testimony that I don't know my craft.

 

[Nick Zentena]

Replenishment of fixer does lower silver. If you have 1litre of fixer removing 100ml of old fixer and replacing it with 100ml of replenisher will lower the silver content by 10%. Assuming the silver is evenly dispersed in the fixer.

Two bath is because fixer stops fixing 100% very quickly. I'm sure somebody else can pull the studies out but fixer very quickly goes from good to almost good. Good enough to do most of the work in the first bath but not good enough to finish the job.

 

[Ryuji]

Replenishing isn't very hard. You just pour off some of the old and add some of the new. OTOH for B&W I'd just suggest doing two bath fixing.

This is very true of developers that are properly designed for bleed replenishment. However, replenishing fixing bath is ineffective unless online silver removal system is used in conjunction. Otherwise, it is more economical and effective to use the fixer to exhaustion and replace the bath entirely. If there is need to make up for the fluid loss, use water to top up, although topping up with fresh fixer will give no harm.

 

[lowellh]

Nick, Modern Rapid Fixers do not stop fixing quickly! The capacity of fixer is based on the amount of available Ammonium thio Sulfate in the solution. They are easily replenished with working strength fixer. They do not have to be cycled through a silver recovery unit unless you are using a "closed loop" recycling system. If that is the case the buffering chemical and sodium sulfite levels need to be rebuilt. In commercial applications, it is the same fixer sold in the retail market and constantly replenished to maintain the integrity of the system. There are usually two reasons for the fixer in a commercial application to "go bad", under replenishment or improper mixing and addition of hardener to the fix.

 

[Ryuji]

Nick, Modern Rapid Fixers do not stop fixing quickly! The capacity of fixer is based on the amount of available Ammonium thio Sulfate in the solution. They are easily replenished with working strength fixer. They do not have to be cycled through a silver recovery unit unless you are using a "closed loop" recycling system.

What you said is true for fixation for non-archival materials at elevated temperature in some processing machines. But in reality, at room temperature processing of fine art b&w materials with small tolerance for the residual silver-thiosulfate complex in the paper, the fixer may keep fixing but the removal of fixing reaction products from the emulsion and paper base become increasingly difficult, and this is the reason why we should watch out for the silver concentration in the fixing bath. The processing capacity may be increased by use of washing aid, but still the fixer is not to be used endlessly.

 

[pentaxuser]

This is very true of developers that are properly designed for bleed replenishment. However, replenishing fixing bath is ineffective unless online silver removal system is used in conjunction. Otherwise, it is more economical and effective to use the fixer to exhaustion and replace the bath entirely. If there is need to make up for the fluid loss, use water to top up, although topping up with fresh fixer will give no harm.

Ryuji

If I have understood you correctly and I may very well not have, you seem to be saying that fixer replenishment doesn't work. I have no knowledge of photo chemistry so in layman's terms can you explain why it doesn't work.

What Nick said about replenishment seemed to make sense in that if a litre of fixer can hold only so much silver, I had assumed that,say, each 100ml would hold a certain proportion of that max amount of silver. If a 100ml is dumped every so many prints and replenished then isn't the replenished fixer then able to holds more silver?

Certainly that's the principle on which a company like Nova sells its fixer. It even gives a recommended replenishment rate.

Is it completely wrong and misleading the consumer? If the replenishment rate is say 10 prints of 10 x 8 per 100ml of fixer, should they be advising non replenishment and dumping after 100 prints or whatever the max number of prints 1 litre of fixer can cope with?

Thanks

pentaxuser

 

[lowellh]

Ryuji, What do you mean by the term "non archival" materials? No one processes to be non archival. When you replenish any solution, the laws of thermodynamics apply. Replenisher, by definition, reduces the concentration silver thiosulfate complexes in the solution.
How is the capacity of the fixer increased by use of a wash aid?
Please keep in mind, "Archival" is defined in the ISO Standard by washing not fixing.

 

[Ole]

...
How is the capacity of the fixer increased by use of a wash aid?
Please keep in mind, "Archival" is defined in the ISO Standard by washing not fixing.

I believe you answered your own question there.

 

[Donald Miller]

I believe you answered your own question there.

I think that the assertion that was previously made still stands. I have the same question. How does the use of a wash aid extend the life of a fixer...considering that the wash aid is used after the fixing bath.

 

[Nick Zentena]

I think what he means is

Using fixer past a certain point leads to greater fixer reaction products in the print. The fixer itself can't deal with these.

The better washing will hopefully remove these products.

So the wash aid lets you get longer fixer life by cleaning up after the fixer.

 

[Ryuji]

If I have understood you correctly and I may very well not have, you seem to be saying that fixer replenishment doesn't work.

I didn't use the word "doesn't work" but instead I said "ineffective" and less "economical."

What Nick said about replenishment seemed to make sense in that if a litre of fixer can hold only so much silver, I had assumed that,say, each 100ml would hold a certain proportion of that max amount of silver. If a 100ml is dumped every so many prints and replenished then isn't the replenished fixer then able to holds more silver?

I'll use very oversimplified model for illustrative purpose only. Suppose 10 parts of fresh fixer can fix 100 prints. By replacing 1 portion of the exhausted fixer, you'll end up with 90% exhausted fixer. Does this fixer fix 10 prints before going to exhaustion just as well as the fresh fixer? The answer is no.

By the above scheme, the fixer is always operating between 90% exhaustion and 100% exhaustion, except for the initial period when the exhaustion level go from 0 to 90%. This is far worse than using the fixer until game over, and then replace it with fresh one. This way your fixer goes from 0 to 100% exhaustion, and then resets to 0% exhaustion.

This is why it is best to dump the entire bath of exhausted fixer and replace it with 10 parts of fresh fixer to fix another 100 prints.

In fixing bath, lower silver concentration is always better. There is no optimal silver concentration that is greater than zero.

In developer, this is different. By making a suitable developer, for which optimal KBr concentration is say 1.0g. In this case, say each 80 square inch of film releases 50mg of KBr (this is not too far from reality), and so if you develop 2 rolls in a liter, the KBr concentration will be 1.1g/L. So you discard 90ml of the developer and replace it with fresh replenisher containing 0g/L KBr. Then your KBr concentration comes back to the optimal 1.0g/L. This way you can maintain constant developer activity for a long time, as long as other factors such as loss of developing agents, loss of sulfite, pH drop due to development, etc. are accounted for by the adjustment in the formulation of replenisher.

Therefore, even though the operation is similar, and the same word "replenishment" is used for both cases, the actual design strategy of the processing solutions are very different.

I own a Nova processor and I use it, but I think replenishing the fixer is not the best option as I described above. One thing with Nova is that it's much easier to keep replenishing than replacing the whole solution. Indeed I replenish developer and stop bath but I don't replenish fixer, again for the same reason I described above. I just carefully dump the exhausted fix, then fill up with water, dump again, repeat a few times, and then pour in 500ml of Clearfix concentrate, then slowly top up with water while stirring the slot with a stirring rod. (The concentrate solutions don't mix very well in slot processor unless you use a long stir rod that reaches to the bottom. A cheap long bamboo chopstick will do.)

Is it completely wrong and misleading the consumer? If the replenishment rate is say 10 prints of 10 x 8 per 100ml of fixer, should they be advising non replenishment and dumping after 100 prints or whatever the max number of prints 1 litre of fixer can cope with?

I don't know if I would use the word "completely wrong" but they are recommending less efficient and less economical approach. As you see I ignore their recommendations on this matter but I have my approach.

Dead Link Removed

Dead Link Removed

 

[Ryuji]

I think what he means is

Using fixer past a certain point leads to greater fixer reaction products in the print. The fixer itself can't deal with these.

The better washing will hopefully remove these products.

So the wash aid lets you get longer fixer life by cleaning up after the fixer.

You are the most sensible man in this thread with good grasp of technical information.

 

[Ryuji]

I think that the assertion that was previously made still stands. I have the same question. How does the use of a wash aid extend the life of a fixer...considering that the wash aid is used after the fixing bath.

It is just like Nick said.

Removing undeveloped silver halide is only half of the story. Only very fresh fixer can remove harmful fixer reaction products by plain water wash.

As the fixer gets partially exhausted, the fixer may dissolve undeveloped silver halide crystals but the fixer doesn't completely react to ensure that the reaction products can be washed by plain water. This is why the fixer's processing capacity (for archival materials) is very small if you don't use two-stage fixation or washing aid.

You can keep using the fixer until the silver concentration goes further up, as long as (1) you don't care about the archivally harmful effect of incomplete fixing reaction products OR (2) the incomplete fixing reaction products are somehow removed by a later step. Washing aid does the (2) above and it is a very useful processing step to maximize usable processing capacity of the fixing bath for archival prints.

 

[lowellh]

Gentlemen, Developer exhausts. The developing agents are expended in the process. Fixer DOES NOT exhaust, it becomes saturated with silver. The higher the level of silver in the fixing solution, the slower the fixing process becomes. The fixing reaction is a completion reaction, it does not partially react. How are "harmful" fixer reaction products defined? How are they harmful? Wash Aide ( sodium sulfite) in the washing process is a physical one not a chemical one. The Sodium sulfite in water forms ions that physically "bump" the impurities out of the emulsion, again, physical not chemical.
The capacity of the fixing solution is based on the amount of thio sulfate in the working strength solution.

 

[Ole]

Fixing is a little more complex (pun intended) than most people realise.

First of all, thiosulfate does not dissolve silver halides: It only ensures that what little is dissolved, stays in solution. Even if silver halides are said to be insoluble in water, a very small faction will be disolved at equilibrium with the solid. Thiosulfate binds to the dissolved silver ions, thus skewing the equilibrium so that more can dissolve. Ammonium thiosulfate works faster, since ammonium ions can also bind to silver ions.

The thiosulfate is not consumed in this reaction, but it is also "removed from active duty".

The thiosulfate binds to the silver by forming "complex ions", with different numbers of thiosulfate ions bound to each silver ion. These different complexes have different properties, like solubility and mobility in the gelatin emulsion as well as in the paper base of fiber prints.

To get an archival result it is not enough to dissolve all the silver halides, the silver complex ions must also be removed from the emulsion or a stain will result when the silver reacts with - well, basically anything.

Fixing "goes to completion" only if we disregard the further reactions in the solution, which make it possible to remove more of the silver from where it can lead to harm. The more free thiosulfate there is in the fixer, the better.

The less mobile complexes can also be removed by prolonged washing, or by addition of fresh thiosulfate, or by aid of wash aids which displace the silver/thiosulfate complexes in the emulsion.

 

[Ryuji]

Gentlemen, Developer exhausts. The developing agents are expended in the process. Fixer DOES NOT exhaust, it becomes saturated with silver. The higher the level of silver in the fixing solution, the slower the fixing process becomes. The fixing reaction is a completion reaction, it does not partially react. How are "harmful" fixer reaction products defined? How are they harmful? Wash Aide ( sodium sulfite) in the washing process is a physical one not a chemical one. The Sodium sulfite in water forms ions that physically "bump" the impurities out of the emulsion, again, physical not chemical.
The capacity of the fixing solution is based on the amount of thio sulfate in the working strength solution.

I'm afraid that your understanding of fixer capacity and reaction is not very close to the truth. I suggest you study any of the standard photographic chemistry textbooks on this matter before you proceed on this discussion. If you are in Boston area I would be glad to give in-person lecture on this, but I don't have time or energy to do this online.

If the silver concentration in the fixer reaches a certain point, fixer is said to be exhausted because it is incapable of completing the fixation reaction in any reasonable time. Fixing reaction is a multi-step reaction between silver halide and thiosulfates and the difficulty of complete fixation in silver-loaded fixing bath can be easily explained by simple chemical principles (Le Chatelier principle and other things you learn in undergrad level chemistry).

Harmful intermediate is argentomonothiosulfate. This compound should be comverted to argentodithisulfate or even argentotrithiosulfate in certain cases, before they can be washed out of the gelatin layer and support. Argentomonothiosulfate is not very soluble in plain water but it is soluble in sulfite solution.

When prints fixed incompletely in partially exhausted fixer is transferred to a second fresh fixing bath, this compound is converted to soluble higher order complex, which can be washed out by plain water.

When prints fixed incompletely in partially exhausted fixer is transferred to a plain water washing bath, thisulfate ion is removed from the print faster than other silver-thiosulfate complexes, and therefore argentomonothiosulfate will not be removed in absence of help from fresh fixing bath or sulfite washing aid.

 

[Ryuji]

The less mobile complexes can also be removed by prolonged washing, or by addition of fresh thiosulfate, or by aid of wash aids which displace the silver/thiosulfate complexes in the emulsion.

Ole, most of what you said are correct except the part quoted above. Argentomonothiosulfate is less soluble in plain water than silver halide used in paper emulsion, and prolonged plain water wash is ineffective. Also, adding more thiosulfate to an exhausted (silver-loaded) fixing bath is also ineffective, unless the silver is removed from the fixing bath.

Practical ways to solve this are: (1) replace the fixer with fresh bath with low-silver concentration; (2) use two-bath fixiation with fresh fixer in the second bath; (3) use washing aid.

There is certain limitation in each approach. (3) is simple and cheap but it can't go on forever. (1) is very effective but then the fixer would have to be replaced a lotmore frequently and it is not very economical. (2) is very effective and economical but the processing line becomes more cumbersome.

 

[Ole]

Ole, most of what you said are correct except the part quoted above. Argentomonothiosulfate is less soluble in plain water than silver halide used in paper emulsion, and prolonged plain water wash is ineffective. Also, adding more thiosulfate to an exhausted (silver-loaded) fixing bath is also ineffective, unless the silver is removed from the fixing bath. ...

Thanks for the correction, Ryuji.

At least I got the main thing right - that it's a lot more complicated than some people seem to believe!

 

[Photo Engineer]

Every post here has some element of truth and some are entirely correct.

But, all of them miss certain salient points such as pH and swell.

As silver forms higher order complexes with thiosulfate, the complex becomes larger along with becoming more soluable, and therefore it diffuses out of the coating more slowly even though it dissolves better.

Using ammonia increases solubility of these complexes, and if it substitutes for a thiosulfate, it makes the soluable complex smaller and therefore it diffuses outward more rapidly.

The more alkaline the fix, the better the diffusion outward, due to the higher gelatin swell, but then you can become so alkaline that the gelatin becomes too soft or the silver complexes begin to fight with silver hydroxide formation but then this is in competition with ammonia. You may end up with compexes of hydroxide and thiosulfate along with silver and ammonia.

Hydrogen bonding with the complex also modifies solubility and diffusion.

In effect, this is a complex (pun alert) situation which no single answer can satisfy.

The simple test is to add Potassium Iodide hypo test solution to your hypo. If a voluminous yellow precipitate forms, the hypo solution is exhausted, but if just a tiny yellow haze forms, it is ok. If the haze forms add a little fresh hypo solution, but if the heavy precipitate forms, you will probably have to add at least 50% or so of fresh hypo solution.

In addition, seasoning or using a developer changes the balance of chemistry and replenishment is intended to restore the developer to a state that gives the 'original' sensitometry. Changes in the film caused by the developer cannot be fixed after the fact.

Fixer, when used, generally does not affect sensitometry and any errors can be rectified if caught quickly enough, such as before yellowing or fading takes place. This is a generalization though.

Any post-fix bath containing sulfite relies on the sulfite to clean up any remaining silver halides or silver hypo complexes. Since sulfite is a poor silver halide solvent, it does not do a very good job if the silver content of the material undergoing treatment goes above a certain level, or if the iodide content is too high. In other words, the post baths sometmes don't work, and the post baths can also be exhausted by carrover and pH change.

PE

 

[dancqu]

Please keep in mind, "Archival" is defined in the ISO
Standard by washing not fixing.

That's an important point. The now defunct Ilford
Archival Processing Sequence claimed archival results
using a single bath fix used to levels of silver they claim
as a maximum level for commercial processing. G. Haist
may not agree.

I've not actually seen ISO standards for silver
or thiosulfate levels in finished materials, archival
or commercial. Not that I recall. I wouldn't be
surprised if they did not exist.

Two good means for checking are in use in darkrooms.
The ST-1 test uses sulfide to check for residual Silver.
The HT-2 test uses silver to check for residual Hypo.
From all that I've read of those two tests, if NO,
ZERO, stain is produced then all is OK.

All in all, for peace of mind, recommended methods and
the two tests I've mentioned can be employed. Dan

 

[Photo Engineer]

Dan;

ISO standards exist, but since use of peroxide and ferricyanide or other oxidants has been rather discredited, the committee has been redoing the standards. They are not prepared to release or discuss them with others as of yet, and they are a compromise as usual.

Just one example, Fuji insists that ~500 FC is correct to test fading, but EK insists that ~180 FC is correct. One represents a typical office environment, and the other represents a typical home environment. There are reasons to go either way, but, not surprising, one shows Fuji products to be better and the other shows EK products to be better (guess which is which and you get only one guess).

In any event, ISO standards exist and Grant got his information from a 'higher' source at EK. He was not a primary worker in actual image stability and mechanisms although he and I both participated in the work.

Suffice it to say that Ilford, Kodak, and Fuji have diligent workers that are trying their best to give us a reliable, high quality archival process with the products to back them up. This covers both color and B&W.

Simon may want to comment on the work of Dr. Beveridge of Ilford, which I have heard is superb in the area of B&W image stability.

PE

 

[Helen B]

...
Please keep in mind, "Archival" is defined in the ISO Standard by washing not fixing.

Lowell,

ISO 18901-2002 defines image stability in terms of residual silver compounds as well as residual thiosuphate (among other properties not relevant to this discussion). 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.

The reference specimen, for making residual silver comparisons,

"shall be:

of the same film type, preferably the same lot;

fixed successively for 5 min in each of two duplicate fresh fixing baths containing 240 g/l of sodium thiosulfate (Na2S2O3-5H2O);

washed for 30 min in running water that is flowing at a rate that will fill the vessel once every 5 min."

This standard, as already mentioned, "is not applicable to films where the silver salts are removed by means other than thiosulfate solutions."

And:
"Films shall be fixed in solutions containing either sodium thiosulfate (hypo) or ammonium thiosulfate. Hypo-eliminating agents containing oxidizing agents such as peroxides or hypochlorites shall not be used.

NOTE Hypo-eliminating agents contain chemicals, usually strong oxidizing agents, which decompose thiosulfate. These are to be distinguished from hypo-clearing baths, which are high ionic strength salt solutions. These facilitate the washing of thiosulfate from the film, but do not chemically alter the thiosulfate."

Best,
Helen