Buffering Neutral Fixer

Discussion in 'B&W: Film, Paper, Chemistry' started by Rafal Lukawiecki, Mar 10, 2013.

  1. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    I'd like to mix a neutral rapid fixer, relatively low-odour, that can keep its pH about-neutral when used after a citric acid stop bath. I've researched APUG, and I can see many references to a buffered fixer by Ryuji, however, all of those referenced pages seem to have been deleted, and are not to be found elsewhere. I suppose there were reasons why that recipe was removed from APUG and from the public domain, which is why I am not posting those thread references, and I am not asking for it. The only Ryuji recipe for a neutral fixer is http://www.apug.org/forums/forum226/33383-neutral-rapid-fixer.html, which is similar to the below one, MF-2, except it uses 5g sodium metabisulfite instead of boric acid, but it seems to me that it may not have much of a buffer. Other fixer discussions do not mention buffering much.

    However, I found the following, somewhat alkaline, recipe MF-2 on Flickr:

    Ammonium Thiosulfate - 120g (200mL of 60% solution)
    Sodium Sulfite - 15g
    Borax - 5g
    Boric Acid - 5g
    Water to make 1L (pH 8.0)

    I remember reading somewhere that borax, triethanolamine, or disodium phosphate would make good buffers for a fixer, and I am aware of Ryuji's use of salicylic acid combined with triethanolamine as a buffer (and a chelating agent I think) for his developers.

    I could go ahead and adjust the proportions of borax, metaborate, and either boric acid or sodium metabisulfite until I get pH of about 7, but I am concerned that in doing so I would not be making a good buffer, but just using up the buffering ability of such a mix to arrive at a desired pH, which sounds counterproductive to me. Do I need a quick lesson in pH 7 buffers suitable for fixers?

    Could the collective chemical mind of APUG make a suggestion as to a sensible neutral buffer to use for an ammonium thiosulfate/sodium sulfite rapid fixer?

    As an adjunct to this, I am curious about a buffer for a citric acid stop bath. I guess I do need a lesson in buffers.
     
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  2. michael_r

    michael_r Subscriber

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    What is your reason for needing this? By the way you might want to try TF-5 which is very close to neutral. PE was involved in its design.
     
  3. Rudeofus

    Rudeofus Subscriber

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    Before you load your fixer with all kinds of extra compounds, go read what "ionic strength" means and what that means to fixers. Long story short you can really slow down fixer action if you add too much extra stuff. That's why most fixers don't include much buffering and why the weak buffering that is there comes from compounds which are needed anyway: Sulfite/Bisulfite.

    If you are concerned about pH stability, think about a wash step before fixing. Citric Acid stop bathes are usually pretty dilute so they shouldn't mess up too much. I'd be more concerned about Ammonia smell from a pH 7 rapid fixer ...
     
  4. Gerald C Koch

    Gerald C Koch Member

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    The pH would have to be considerably higher than 7 before any ammonia gas is released.

    The pH of an ammonium thiosulfate solution 60% is already between 7.5 aqnd 9 add to this the addition of sodium sulfite and you already have a buffered fixer without the need for any additional buffering. Fixer will wash out faster if the fixerr is slightly basic.

    Acidic fixers are really only needed when they must contain alum as a hardening agent.
     
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  5. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Michael, I should have explained my reasons, but I didn't want to bore anyone with the details of my current process, which I am aiming to optimise—tinkering to save time, I suppose, and to cut down on acetic acid fumes, though I don't want to replace them with plenty of ammonia, either, hence the desire to stay neutral, rather than alkaline. As Gerald points out, I believe I have no need for an acidic fixer, as I have no need for hardeners. Secondly, I tend to tone, in KRST, at the end of my printing session, sometimes twice in a day, and I would like to make that step even more immediate at times. Sine I tested, I know my current fixing is good, in terms of residual silver halides, so I should be able to dispense with, or shorten, the rinse prior to KRST, which is currently necessary due to the acid in the fixer, which Se does not like. However, I want to stay with a rapid fixer, hence ammonium thio in a neutral setting appeals to me. Finally, I am comfortable with a citric acid stop, and I want to continue using it, without pushing the fixer into acidic territory, hence my request for a suggestion of a buffer. For what it is worth, I fix twice, 45 s each plus 15 s drain time, and I like using the first fixer till it has about 3 g Ag/l, hence the safety net of the 2nd fixer bath to make the argentothiosulfates easier to wash out. I also use a sodium sulfite washing aid after KRST. In the long run, I am keen to experiment with removing the second fix bath, since I think the thiosulfate in KRST, and then a fresh washing aid, perhaps slightly prolonged from my current 3 min to 5 or so, may do a good enough job of getting rid of the fixing byproducts. But first, I just want to try with a neutral one.

    Unfortunately, shipping TF-5 to Ireland is prohibitively expensive, due to weight, and I cannot find it sold here...

    Gerald, would you be able to estimate how many ml of citric acid stop would it take to bring 1l of a mix of (ammonium thiosulfate 120g + sodium sulfite 15g + sodium metabisulfite 5g) below pH 7, say to 6.5?

    Rudeofus, thank you for your kind suggestion to read up on ionic strength. I have spend an hour or so picking up on the subject on Wikipedia, and I have browsed a Kodak patent that talk about this metric in the context of fixers. I will be reviewing Mees later today, to find out more, as I am just reading that amazing book. All I can understand, so far, is that increase in ionic strength will affect photographic material gelatin swell which may also reduce fixing rate. What I am unable to determine, however, is how significant would that effect be, especially with a buffer designed for the purpose.

    Since you know about ionic strength issues in fixing, may I ask you, please, to estimate what would be the impact, in terms of how much I would have to extend fixing time when using a buffer such as 5g Borax + 5g Boric Acid in 1l of the fixer, such as the one mentioned above? Do you have any other suggestions as to where I should read more about ionic strength and fixers?
     
  6. Gerald C Koch

    Gerald C Koch Member

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    Such a calculation would be very hard to do as it involves 5 variables which includes the pH of the ammonium thiosulfate 60% solution which is variable from batch to batch. But the amount of citric acid carryover should be small and of little consequence. Just let the prints drain well before putting them in the fixer.

    If you are concerned about the pH of the fixer it is easy to check it periodically with some pH paper of the appropriate range. If it becomes too acidic then just add a small amout of base.
     
  7. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Thank you, Gerald. I will keep notes on the evolving pH of the fixer as I work with it, what an obviously simple suggestions, many thanks, indeed. I had no idea that ammonium thiosulfate 60% solution comes at different pH, batch-to-batch. I have assumed it to be more-or-less constant. I suppose this means even Ryuji's recipe needs to be adjusted to get it into pH 7 upon making, I suppose by varying the amount of sodium metabisulfite.

    I also want to thank Rudi for his PM suggestions re ionic strength.

    Still, why do I have a feeling I am rediscovering something that must have been done by quite a few others?
     
  8. Mr Bill

    Mr Bill Member

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    Hi Rafal, I don't know how much processing you do, but it might be worth considering the option of replenishing your fixer.

    This is the standard method used in high-volume processing. Whatever is wrong with the tank solution is fixed with the right amount of the right replenisher. (Replenisher volume is normally based on area of the material being processed.)

    Since you indicated that you could mix to a certain pH aim, and you know how to limit your first fixer to a certain silver-content, I'm thinking that you could probably customize your own fixer replenisher. (I wouldn't normally suggest this idea, but it sounds like you're having fun formulating.) Essentially you would make a fix replenisher that counteracts the pH-lowering effect of the stop bath.

    If you're interested, and want some suggestions on how, I'll be glad to kibitz.

    ps. of course, Gerald's suggestion is much simpler and gets right to the point.
     
  9. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Thank you, Bill, for making the suggestion about replenishment. I have researched it in the past, and I understand that fixer replenishment only works in conjunction with a silver recovery option, as no amount of replenisher will remove the silver that is already in the fixer, unless you remove the solution itself—if this is incorrect, please let me know, as I am eager to know.

    Having said that, I do use a silver recovery device (Silver Magnet from JNanian) to remove a good bit of the silver from the spent fixer. However, what is left gets taken away, as it is has been contaminated with stop bath carryover. I'd be happy to research replenishment too, but for now I am more focused on making a switch from acidic to a neutral one. I'll report my findings as to the pH stability when I have some data, for now I am using up the remainder of my acid fixer. Once that is under control, I would love to recycle/replenish my fixer, as anything I can reasonably do to minimise waste without creating something worse, is high on my agenda.
     
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  10. Mr Bill

    Mr Bill Member

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    Well, although this is correct, it's not the whole story. When you replenish, you don't REMOVE silver, but the fresh replenisher being added will dilute byproducts; thus you control silver concentration by changing the replenishment rate (solution being removed changes volume, but not concentration).

    I don't know that there would be any advantage to replenishment other than the tanks staying in a steady-state condition. You're already doing good by using a 2-bath fixer and John's Silver Magnet. (Anybody doing any volume without something like the Magnet, or better, is missing out in my opinion.)
     
  11. Richard Jepsen

    Richard Jepsen Member

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    To simplify, reduce fumes and process to an archival standard I initiated the following process. Non metol print developer, water stop, TF-4 fix. Fix capacity is (10) 8x10s per L. There are no fumes with this all alkaline process. If I print on 11x14, I introduce a citric stop, water rinse and two tray fix. The citric stop aids in a quick stop with such large paper. I always lightly tone and use a (10) minute wash aid before a 20-30m manual tray wash.

    The down side is lower fix capacity with a one tray line. The positive is a citric stop will be ok when used with neutral fix like Ilford's if processing only (10) 8x10s per L.
     
  12. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Richard, if you do a two stage fix you should be getting a much higher capacity out of the first fixer.

    I believe, but I have not verified in tests, yet, this may also apply when using a single stage fix with a fresh and unoxidized wash aid after fixing, which effectively allows a higher fixer capacity.
     
  13. MattKing

    MattKing Subscriber

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    Would a flowing water rinse between the stop and fix solve your problem?
     
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  15. Richard Jepsen

    Richard Jepsen Member

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    The one stage fix was suggested as a way to simplify with the down side of less capacity. You wrote in a later post the desire to eliminate the second fix.
    I prefer using non metol paper developers. PE suggested an acid stop is required to eliminate developing agents if using metol.

    I recently started to use a weak citric stop for prints larger than 8x10. No irritating fumes were experienced. To reduce solution carry over I use a water rinse after the citric stop and finish with a two fix process. The larger prints (8x12) on 11x14 are to be mounted. In my limited space its easier to use a single tray processing routine when projecting on 11x14. The downside is cleaning the tray between each processed print. Otherwise I use 8x10 trays, water stop, and one fix tray to make it simple.
     
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  16. Doremus Scudder

    Doremus Scudder Member

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    Just a few observations:

    I transfer prints directly from a rapid fix mixed "paper strength" or 1+9 (Ilford Hypam or Rapid Fix, or Kodak Rapid Fix without hardener) to the selenium toner. No problems with staining, etc. The fixer is neutral enough to not need an intermediate rinse. My point here is that mixing your own fixer might be overkill and not get you any better results at the expense of wasted time.

    I use two-bath fixing. Capacity is ca. 40 8x10 per liter. Richard might find it worth it to cut his capacity by 75% for convenience sake, but I do not. The total fixing time remains the same anyway. I really cannot understand the objection to two-bath fixing unless it is the space issue. Maybe there are better ways to deal with not having enough tray space than risking the permanence of your prints or wasting 75% of your fixer. Tray stackers are a pretty good solution and I've used these often for larger prints. Normally however, I solve the space problem by separating the toning from the printing (see below).

    A wash aid is not going to increase the capacity of any fixer. It will speed up washing but it won't chemically change any insoluble silver thiosulfate compounds. You need adequate fixing in fresh fixer to achieve complete fixing. If you want to use single bath fixing and still have optimum permanence, Richard's ten 8x10s per liter is the correct capacity (according to Ilford and others). Two-bath fixing gets around the capacity limitation by having a relatively fresh and uncontaminated second bath that finishes fixing the insoluble compounds left by the first bath after its capacity of ten prints has been reached.

    The amount of thiosulfate in KRST does not make it a fixer, nor does the toning bath function as a fixer. Plus, if you try to use your toner as a second fixing bath, you'll have to toss it when the fixing capacity is reached, well before the capacity of the toner is reached. Uneconomical and environmentally irresponsible. (Do a search for some of my posts on replenishing and reusing selenium toner so you won't ever have to toss it.)

    Commercial fixers like the ones I have mentioned are designed to be used with an acid stop bath. Don't mix the stop bath too strong and drain your prints well before transferring them to the fix and you should be fine. Whether you use one or two-bath fixing, the fix won't die from "acid contamination" before you reach its capacity when transferring directly to the fix from the stop. You don't need a water bath between stop and fix at all; it is completely superfluous. Why would you want a process that added yet another step without getting any better results? (plus, you could use the extra space for a second fixer tray...)

    Indicator stop baths mixed a bit weaker than recommended (2/3 recommended strength or so) do not have much odor and work just fine; they just have a smaller capacity. Toss the stop when it just begins to turn color.

    Neither fix at "print strength" nor a weak stop have a whole lot of "fumes." I notice almost no odor at all except when I mix a fresh stop bath. If you are dealing with a lot of odor, you might need to deal with ventilation problems before trying to find more odorless chemicals.

    To optimize your processing space, you might try dividing your work flow and separate the toning session from the printing. I develop, stop, give fix one, then wash and dry prints. The toning session is a water soak, fix two, toner, hypo-clear and wash. Doing all that stuff at once is just to much and takes too much room. Plus, I can live with the prints for a while and discard the prints that I don't think will make the grade before toning. This keeps me from spending a lot of toning time on reject prints.

    Just some ideas...

    Doremus


    www.DoremusScudder.com
     
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  17. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Matt, Richard, Doremus, thank you for putting your time into sharing your thoughts with me.

    Doremus, you make good points about your process, which clearly works well for you. I am inquiring specifically about making improvements to mine, which is, at the moment, very similar to your current process, yet which I wish to improve by taking advantage of the more recently available knowledge, and the collective wisdom of the community. I hope you will not be offended, however, if I politely question two points, which you have made, and which I think were the core of my inquiry, ie. re-evaluation of the use of sodium sulfite, and the presence of thiosulfate in KRST. I look forward to your, or other chemists' feedback, as I am not a chemist myself, although I do have an appreciation of the basic photochemical concepts.

    Ilford states: "Use a single fixing bath plus a washing aid. The number of prints through the single fixing bath can be increased to approximately 40 8x10" prints per litre working solution." in this document, page 3, right-hand column, point 3. This is in contrast to what they say is the capacity without a wash aid: "Fix only a few prints before replacing the fixing bath (approximately 10 8x10 inches prints)."

    Similarly, you will find an extensive comparison of fixing and the fixer capacities, with and without the use of a washing aid, in this publication of Digital Truth, which is very similar to Ryuji Suzuki's findings, and on the Pure Silver mailing list. That document states: "Note that the processing capacity of fixer is considerably lower if fiber prints are processed without using a washing aid" and the capacity numbers show between twice and four times larger capacities of the fixer when a wash aid is part of the process. I think I saw a Kodak reference, similar to those two, but I cannot find it anymore.

    So, why is the use of a wash aid, such as a 2% solution of sodium sulfite, able to increase the capacity of the fixer to the level almost identical to that achieved when using two-bath fixing? Based on what I have read it has to do with the removal of the silver thiosulfate compounds, as there is very little silver halide left in the emulsion of the paper when fixing even for a shorter time with a non-fresh fixer, but one that isn't exhausted, yet. I was re-reading Mees today (chapter 13, Fixation and Washing), while preparing to write this post, and I am always amazed by the complexity of the seemingly simple fixation process. However, I can surmise that two things are relevant to my question: as long as we are using fixer that is no longer fresh, but not exceeding silver levels of 2g/litre (so about the capacity of 40 8x10 sheets in ammonium thiosulfate 12% solution, such as a typical rapid fixer), there will be a build up of argentothiosulfates, or if you prefer silver thiosulfate compounds, including those that Mees refers to as salts of the argentothiosulfuric acids (page 512 edition 1 of The Theory of the Photographic Process), or what Gudzinowicz calls monoargentomonothiosulate, monoargentodithiosulfate, and monoargentotrithiosulfate, while describing their increasing levels of solubility. From what I read, those compounds are likely to migrate from the emulsion to the solution only when a fresh fixer is used, less than 0.5g silver/l (up to about 10 sheet 8x10 per l, which you mention), or when the print is moved to the second, such fresh fix bath. A fixer than is more exhausted will cause some of those compounds, including the more soluble ones, to adsorb to the silver grains, and also to the other layers in fibre paper, especially if fixation is anything but very brief.

    However, what complicates this picture is the fact that it is even the more soluble argentothiosulfates will also form anew on the surface of the emulsion, if the fixer is sufficiently unfresh, as mentioned in this patent by Armstrong, in which he describes the efficacy of wash water being increased by the presence of certain levels of impurities, due to ionic exchange. This is also discussed in the 9th ed of "The Manual of Photography" by Jacobson, page 294: "In the presence of a high concentration of soluble silver, or low concentration of free thiosulphate, when the fixing solution is nearing exhaustion, the complex sodium argentothiosulphates may become adsorbed,or "mordanted", to the image. These are difficult to remove by washing." Notice the comment "difficult" rather than "impossible".

    Now we come to sodium sulfite. Not much I could find, but there are references to it acting this way: "sulfite can desorb not only unreacted thiosulfate but also sparingly soluble and adsorbed argentomonothiosulfate complex" (arguably not the most reliable source, Photography Wiki). I can see references in David Locker's paper, but I do not have access to it, and Wiley quotes a low price of just $12,346 for a one-time access. However, since Ilford, and others, are quoting this action of sodium sulfite, there must be a reason, and I would love to know what it is, or if something else is at play, that increases the effective capacity of the fixer, while maintaining archival/optimum permanence.

    Doremus, I hope I did not make it sounds like I was ever suggesting that KRST is a fixer. If I did, please accept my deep apologies for not making myself clear: indeed, KRST is a well-known selenium toner, and not a fixer. If one were to use it on a not fully-fixed sheet, staining would result, as selenium would react with silver halides.

    I am merely curious, however, if the presence of 3-5% of fresh ammonium thiosulfate in a working strength KRST (it holds 25-30% in stock according to its MSDS), which is almost the same as a paper-strength rapid fixer, would have a positive effect on the process of desorbing of the complex argentothiosulfates. I hope you will agree this is a valid question to ask, and I would be surprised if no one has thought of it before. I realise, however, that the action of the fixer that is responsible for the conversion of the silver halides to argentothiosulfates is easily retarded by the presence of other ions, such as chloride, bromide, and especially iodide, but I have no idea if selenium would have this impact on the desorbing function. Perhaps you could help me in this.

    I very much appreciate your concerns for the environment, and I have, for many years, read your posts here and on the other forum. Perhaps you may have noticed my posts about recycling and environmentally sound removal of photographic chemistry, as it is a subject of great importance to me, and to the place where I live. I trust you see that there is an environmental aspect to my quest in process optimisation: removing a fixing stage and replacing it with something many of us do anyway (wash aid) will cut down on disposed fixer on every 2-stage final rotation, regardless of what is done with the toner.

    I look forward to your comments, and I apologise to all chemists for any shortcomings in my post.
     
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  18. Richard Jepsen

    Richard Jepsen Member

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    [QUOTEIlford states: "Use a single fixing bath plus a washing aid. The number of prints through the single fixing bath can be increased to approximately 40 8x10" prints per litre working solution." in this document, page 3, right-hand column, point 3. This is in contrast to what they say is the capacity without a wash aid: "Fix only a few prints before replacing the fixing bath (approximately 10 8x10 inches prints)."][/QUOTE]

    The ilford 40 print reference is for processing to a commercial archival standard (7-10) years. If you use a wash aid you may extend the Commercial capacity of a one tray fix. The fix has a capacity to process maybe 80 to 100 prints but as more prints run through the fix the more silver thiosulfate compounds build up reducing print life.

    If you limit fix capacity to (10) 8x10s per L, you don't need a wash aid to obtain optimum permanence without toning. If you tone, you must use a wash aid for optimum permanence.

    I'm a simple guy. If your capacity is high, you can explore ways to recover silver. There seems to be a desire for one fix tray and higher capacity. One could just use RC paper which allows higher capacity and uses less water.
     
  19. Richard Jepsen

    Richard Jepsen Member

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    The ilford 40 print reference is for processing to a commercial archival standard around (7-10) years. If you use a wash aid you may extend the Commercial capacity of a one tray fix. The fix has a capacity to process maybe 60 to 80 prints but as more prints run through the fix the more silver thiosulfate compounds build up reducing print life.

    If you limit fix capacity to (10) 8x10s per L, you don't need a wash aid to obtain optimum permanence without toning. If you tone, you must use a wash aid for optimum permanence.

    I'm a simple guy with a dry unvented DR. If your print capacity is high explore ways to recover silver. There seems to be a desire for one fix tray and higher capacity. Recommend RC paper which allows higher fix capacity and uses less water.
     
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  20. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Richard, did you have a look at that Ilford page? My reading is that they describe 3 equivalent approaches in the section on the right of page 3, specifically equating with each other: 1. Fixing up to 10 sheets of 8x10 in 1l. 2. Fixing in a two bath fixer. 3. Fixing up to 40 sheets in one bath when using washing aid.

    Since 10 sheets per litre is what you describe as archival, and since they suggest that is equivalent to 40 sheets with wash aid, it would seem to imply that 40 plus wash aid has to be as archival as 10 without it. Digital Truth seems to suggest that too.

    Perhaps I am not reading that correctly...
     
  21. Doremus Scudder

    Doremus Scudder Member

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    Rafal,

    Richard is correct about the commercial vs. "archival" standards. I'm not sure why Ilford says that a wash-aid will increase fixing capacity; I've really never seen convincing evidence that it can. What it can do, however, is help wash out compounds that might discolor more quickly. Take a look at this document
    http://www.ilfordphoto.com/Webfiles/2006130218312091.pdf and look at the section on silver concentration starting on pg. 4 bottom left. That should explain everything.

    Personally, I think the information about fixers and capacities is more confusing than necessary and that the manufacturers are partly to blame for disseminating ambiguous and sometimes erroneous information. A wash-aid is largely sodium sulfite with a bit of buffering; it is not a fixer, will not change insoluble compounds to soluble and really cannot, therefore, increase fixer capacity as far as I can see. If someone has evidence to the contrary, I'd really like to see it... I don't seem to be able to find Ryuji Suzuki's document to read (which I would like to...). However, I do know that much of his research has been questioned by others on this forum much more knowledgeable than I, so I might tend to take his findings with a grain of salt till I saw some peer review. There may be a way that the sulfite helps "detach" some of the mordanted argentothiosulfates from the image silver, but I haven't seen a lot about this anywhere. Personally, I'd rather not rely on the wash aid to ensure proper fixing of my fiber-base prints... I'll continue to use two-bath fixation and err on the side of undershooting the capacity.

    I don't know if the presence of ammonium thiosulfate in KRST helps in desorbing the argentothiosulfates... In fact, I'm not really sure why it is present in the toner to begin with. As you know, I replenish and reuse my KRST. I have gallon jugs that have been going for more than five years (more like 10). I'm sure that the ammonium thiosulfate in these toning solutions is as good as gone, but they still tone just fine (and don't have the annoying ammonia odor either). I'm curious as to what the ammonium thiosulfate is there for in the first place.

    And, I'm not a chemist either, although I have a few university-level chemistry classes behind me and I've been reading about and dealing with photo chemistry for some years now. I would always defer to Gerald Koch or PE or any of the other experts on this forum. My responses here are as much about learning as about giving information to others.

    My main point in my previous post, however, has less to to with chemistry and more to do with using time and resources wisely. It seems to me that you are spending an awful lot of time and effort trying to compound your own fixer and invent a new fixing process. Kodak (under Haist and others) and Ilford have done the research on fixers much more extensively and better than I could ever hope to do without dedicating a career to photochemistry and experimentation. I am happy to use their research and conclusions. There are a number of well-documented ways to fix and tone properly. Maybe you could spend your time better using one of those? Unless, of course, your goal is to explore photochemistry and fixer compounding. For me, I'll use my limited time to make prints using time-tested methods. I don't have time to spend re-inventing the wheel, so to speak.

    And, never any offense taken! You need not apologize to me about a lively exchange of ideas.

    Best,

    Doremus
     
  22. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Doremus, thank you for your kind observations, I appreciate them. I don't find that compounding my own developer, or fixer, takes much time at all. As ammonium thiosulfate is a liquid, I find it is, actually, a very fast procedure. Further, it is not taking an awful lot of my time and effort. I do it, because I do enjoy this part of photography, albeit not as much as the creative part. Besides, I have a strong scientific background and I have always liked to question things till I understood them. I fully appreciate your points about Haist and others having done this work professionally, but it has been a while since things have progressed, since those days. I am sure there are improvements that can be made, and if no one asks questions, not much is likely to happen. Even because of Ryuji's, and Mark Overton's work, we have those new options, that did not exist a few years ago.

    So, even if it did not apply to my practical desire to improve my existing process, which is very similar to yours, I would still like to understand the impact of sodium sulfite on archival/optimum fixer capacity, or of ammonium thiosulfate in KRST on the same, and about good buffers for a neutral fixer, so as to be even better to the process, results, and the environment. Besides, I find photochemistry, just like the tone reproduction process, truly fascinating, and I yearn to understand the logic behind them, as much as I am able to.
     
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  23. Rudeofus

    Rudeofus Subscriber

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    I've been looking for information on that for a while and came up empty. Fact is that the Selenium in selenium toner is so toxic that few home brewers are willing to mix this toner from raw chemicals - at least I definitely wouldn't. Therefore I don't think we will see much published data on that.
    Among the later books on photo chemistry are Haist's two volumes, and these books don't even mention Ammonium Thiosulfate. Why? Because Kodak would have stomped on Haist's feet if he would published trade secrets! What does this tell me? There isn't much published about modern fixers, at least not with solid data and reproducible results, and even patents are mostly vague or intentionally misleading. Most published data (formulas and test results, not instruction manuals) on fixers is simply not applicable to modern products.

    Testing, at least at amateur level, is much easier for fixers than for developers. Measuring speed and grain (as Mark Overton did) requires some apparatus, and measuring sharpness (reliably!) is beyond reach for most of us. Measuring clearing speed is trivial, and tests for residual silver and hypo are cheap and available, with published recipes. The biggest obstacles to fixer improvements at the amateur level are the cheap availability of commercial rapid fixer (most of the time these commercial soups cost half or less of what the raw chems would cost us!) and the fact that fixers don't visibly improve your prints (for the first 10 years at least).

    Is there a motivation for home brewing or testing fixers? Apparently TF-5 fixer runs circles around standard commercial rapid fixers, especially in terms of working solution life, but it's economically unfeasible to ship it across continents and its recipe is unpublished. A version of Farmer's reducer would be nice that has a working solution life of 8 hours (one really long dark room session). Likewise there is little to no data available for alkaline fixers, or even just simple data points like "what's the most economical way of archival fixing for TMX/TMY that leaves no magenta stain?" or "how can I translate a fixer's clearing time of film X into archival fixing time of paper Y?".
     
  24. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Rudi, I couldn't agree more. I feel that I will have to do a fair amount of testing for the residuals, and just keep a score of what goes through my fixer attempts. Ammonium thiosulfate 60% is not cheap, but it works out the same price (or marginally cheaper) as the ready-made standard, acidic product from Ilford, and much cheaper than the specialised fixers from smaller retailers. However, it is not the price that drives me to do this. Having said that, if I had access to TF-5 at a price similar to what our US friends pay, I probably would not be formulating something of my own.

    Still, I would be researching, and perhaps testing, with regards to the function of sodium sulfite wash-aid on fixer capacities, and I'd love to know if ammonium thiosulfate in KRST helps, but I guess I am repeating myself. I agree with you how curious it is how little there is to be found on those interesting points, which clearly have an impact—or Ilford and others wouldn't have mentioned it.
     
  25. Gerald C Koch

    Gerald C Koch Member

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    Curiously while selenium is poisonous it is also a necessary trace mineral in the body. As Pasteur said it is not the poison but the dose. Here are some of the symptoms that can result from this type of deficiency: cardiovascular disease, nerve degeneration, hypothyroidism, arthritis, anemia and a dry, scaly scalp. A selenium deficiency may even increase the chances of developing some forms of cancer.

    As with many chemicals selenium can be handled safely with proper care. Avoid breathing the powder or skin contact with the element or its solutions. So for the day when commercial preparations are no longer available here is one formula for a selenium toner.

    Kodak T-55 Selenium Toner
    Dassonville T-55

    This formula is similar to Kodak Rapid Selenium Toner.

    Distilled water (50°C) …………………………………………… 750 ml
    Sodium sulfite (anhy) ……………………………………………… 150 g
    Selenium metal, powdered† …………………………………… 6.0 g
    Ammonium chloride ………………………………………………………… 190 g
    Distilled water to make ………………………………………… 1.0 l

    †Exercise care when handling this chemical.

    Method of Preparation

    With adequate ventilation:

    Dissolve the sodium sulfite in the indicated amount of water, then add the
    selenium and boil the mixture for 30 minutes. Allow the solution to cool and
    filter any remaining residue. Dissolve the ammonium chloride in the solution
    and make up to 1 liter with water.

    For use dilute the stock solution 1+5 to 1+9. Immerse the print for 10 to 15
    minutes until the desired tone is achieved and then wash and dry the print.
    The diluted solution does not keep.

    B.L. Twinn, "Some Enlarging Papers and Developers for Miniature Work",
    Photo J. 78: 483
     
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  26. Rudeofus

    Rudeofus Subscriber

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    Thanks for posting that formula, but can you tell me why this one uses no Thiosulfate while Kodak's KRST lists copious amounts of Ammonium Thiosulfate in their MSDS? All this suggests that Thiosulfate improves the real KRST somehow.