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  1. #1

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    Permawash: how long does it last?

    I'm not a chemist and follow the recommendations regarding life of stock solutions of Xtol and Dektol that I mix up.

    I bought a gallon of Permawash a while ago and have been slowly using it up in my FB paper and film processing. I haven't divided it into smaller containers where I can exclude air more easily but have kept it in the gallon jug it came in. Does Permawash last forever or even close as I assume it is still active (time will tell though)

  2. #2
    Nicholas Lindan's Avatar
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    Permawash and all other 'hypo clearing agents' will go off with exposure to air. The S. Sulfite oxidizes to S. Sulfate.

    Use a residual hypo test on washed prints to make sure the stuff is still working. I think one should always use a residual hypo test when using a hypo clearing agent - otherwise one finds out much too late that there is still hypo in the prints.
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  3. #3

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    A good reason to mix your own wash-aid from scratch just before use and discard it immediately afterward. One can simply use sodium sulfite, but a bit of metabisulfite added helps to keep the emulsion from softening too much. Easier and cheaper than buying powders or liquids.

    Here is my formula:

    Hypo-Clearing Agent (One Shot)
    Water (125º F) 1 liter
    Sodium Sulfite 20 g
    Sodium bisulfite (or metabisulfite) 0.2 g
    Water to make 1 liter

    Since the proportions are not too critical, I skip the weighing above and mix with measuring spoons:

    Sodium Sulfite 1 Tbsp (approx. 22.8g)
    Water 1 liter
    A pinch of Sodium Bisulfite or Metabisulfite will lower pH a bit but is not really necessary.

    This is easy to mix on the spot, ok if the water is not too hard (if your water is hard, you may need Calgon, aka EDTA. More sophisticated formulas contain this and sodium citrate, but if you have soft water or mix with distilled or demin, then you don't need them). Essentially the same as the formula above.

    Hope this helps,

    Doremus Scudder
    www.DoremusScudder.com

  4. #4

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    Quote Originally Posted by Nicholas Lindan View Post
    Permawash and all other 'hypo clearing agents' will go off with exposure to air. The S. Sulfite oxidizes to S. Sulfate.
    It is important to be careful about making generalizations about the various washing aids. While the end result, that is the reduction of thiosulfate ion in film and papers is the same, their mode of action is not. If you look at the MSDS for Permawash you will find that it does not contain sodium sulfite.
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  5. #5
    Nicholas Lindan's Avatar
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    Quote Originally Posted by Gerald C Koch View Post
    It is important to be careful about making generalizations about the various washing aids. While the end result, that is the reduction of thiosulfate ion in film and papers is the same, their mode of action is not. If you look at the MSDS for Permawash you will find that it does not contain sodium sulfite.
    .
    From the MSDS:
    AMMONIUM SULFITE Less than 20%
    SODIUM 2-ETHYLHEXYL SULFATE ETHYLHEXYL SULFATE Less than 5%

    Ammonium Sulfite rather than Sodium Sulfite - and this has a different 'mode of action'?. It doesn't oxidize? Sorry, I don't understand your statement, could you elaborate?

    The 2-ETHYLHEXYL SULFATE is a surfactant / wetting agent.
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    There are two products called Permawash and in my haste got the MSDS for the wrong product. Heico Permawash does contain ammonium sulfite BUT at the recommended dilution of 1+43 the sulfite concentration is too low to have the same action as the sodium sulfite in HCA. The action of Permawash is due to the surfactant and other chemicals (trade secrets) where the action of HCA is due to the sulfite.
    Last edited by Gerald C Koch; 11-02-2011 at 04:53 PM. Click to view previous post history.
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    Worker 11811's Avatar
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    Okay, this brings up another question for me.

    The way I understand, there are two main types of wash agent for film and paper. One type simply makes the fixer more soluble in water so that it can be washed out. The other actually binds to or breaks down the fixer into less harmful substances that are more easily washed away.

    I thought products like Kodak's Hypo Clearing Agent are the first type which make fixer more soluble. That is what I have used most often. However, I recently started using Heico Perma-Wash. Is this the "dissolving" kind or the "breaking down" kind?

    Are there any implications of using one type of washing agent over the other that I should be aware of?

    As to the original question, I have been mixing Heico Perma-Wash on a per-batch basis, straight from the bottle, using 23 ml of concentrate to a liter of water. Keeping the bottle tightly capped and stored in the cabinet under my bench, I don't expect there to be much problem with degradation due to age/time/oxygen. At the rate I'm using the stuff, I expect a quart bottle to last a good, long time.
    Randy S.

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  8. #8
    Nicholas Lindan's Avatar
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    Quote Originally Posted by Gerald C Koch View Post
    Heico Permawash does contain ammonium sulfite BUT at the recommended dilution of 1+43 the sulfite concentration is too low to have the same action as the sodium sulfite in HCA. The action of Permawash is due to the surfactant and other chemicals (trade secrets) where the action of HCA is due to the sulfite.
    My experience with Permawash is that it doesn't really work very well even when it is fresh. The idea that surfactants will remove hypo seems to be based more on magical thinking than on any research reported by Haist or Mees. And I remember calculating, as you have, that the Sulfite concentration is much too low. To add insult the MSDS says "Am. Sulfite less than 20%" [italics mine], so what ever it is, it isn't 20% as one might think at first blush - it could just as well be half the amount. I suppose one could evaporate the water and see what's left behind, specific gravity should give the the sulfite to surfactant ratio. I don't think there are any magic trade secret chemicals, but I could be wrong.

    The Kodak HCA formula works very well and the stuff is cheap to make up. My conclusion, after finding the Permawash was not working was to not bother with the stuff any further.
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  9. #9
    Nicholas Lindan's Avatar
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    Quote Originally Posted by Worker 11811 View Post
    The way I understand, there are two main types of wash agent for film and paper. ... I have been mixing Heico Perma-Wash on a per-batch basis, straight from the bottle, using 23 ml of concentrate to a liter of water ... I expect a quart bottle to last a good, long time.
    The two are 'hypo clearing agent' (HCA) and 'hypo eliminator'.

    HCA is based on Sulfite that has been buffered to the pH of gelatine's iso-electric point. The formula for Kodak's version is, as near as anyone can tell:

    5 gm Calgon (only needed if you get white calcium precipitate because of hard water)
    100 gm S. Sulfite
    20 gm S. Bisulfite
    5 gm S. Citrate (optional, off hand can't remember the purpose of it - pH buffer or preservative?)
    Water to make 1l
    Dilute 1:4 for use

    Hypo eliminator is made from Ammonia and Hydrogen Peroxide and has a shelf life measured in minutes. It will remove the last traces of hypo from prints than have been treated with HCA and well washed. Hypo eliminator is no longer recommended - it seems a small residual of sulfur complexes lengthens print life rather than shortens it.

    Permawash is a clearing agent.

    As Gerald has pointed out the working solution of Permawash has less than 5gm of sulfite per liter of working wash, Kodak's formula has 20gm of sulfite per liter.

    If you are using Permawash at a very low rate then the chances are very good the sulfite in it will have oxidized before you have finished the bottle.
    Last edited by Nicholas Lindan; 11-02-2011 at 06:27 PM. Click to view previous post history.
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  10. #10

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    Nicholas, I think i remember reading that the product called Calgon is actually not the same in all parts of the world. I don't remember where I read it. Richard Knoppow from time to time posted on the pure-silver list a formula like the one you have given but with EDTA instead of Calgon. From one of his posts:
    <start quote>
    Sodium Sulfite, dessicated 100 grams
    Sodium Bisulfite 20 grams
    EDTA tetra-sodium salt 1 gram
    Sodium Citrate 1 gram
    Water to make 1 liter
    <end quote>

    And from Ryuji Suzuki's now-defunct web site:
    <start quote>
    Kodak Hypo Clearing Agent contains EDTA and sodium citrate to reduce the calcium scum. With hard water, sulfite in the wash aid forms insoluble calcium scum unless EDTA is added. These are also useful in preventing precipitation of aluminium hardener that may be carried over from the fixer (if acid hardening fixer is used).
    <end quote>

    I just use the sulphite plus a little metabisulphite (=bisulphite). Very cheap if you mix from bulk chemicals, and toss it at the end of the day.

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