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  1. #11

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    Quote Originally Posted by bernard_L View Post
    Thank you all for your comments. I agree it should be OK. But what if the process to produce that bargain de-ionized water (see my OP) has exchanged the ions that the steam iron doesn't like (Ca, Na) for other ions that offset the RedOx balance, for instance. Some picture-taking opportunities happen only once...
    So, I'll buy one, and do an A/B comparison (water "x" versus usual one) with HC110 dilution H, which, being high dilution, should be most sensitive to water quality.
    RedOx is something else, involving a change in oxidation state of at least two and possibly more atoms or groups. When water is purified with de-ionisation, the positive ions (cations) are replaced with H+. This is done by presaturating a cationic resin with an acid such as HCl. When the water is then contacted with it, the sodium, calcium and other positive ions replace the H+ in the resin, and the H+ goes into solution. The opposite is also done, by presaturating an anionic resin with an alkali such as like sodium hydroxide. The OH- anions in the resin are then displaced by the anions such chloride Cl-, sulphate SO4-- etc. As you probably already know, H+ and OH-, when they come together, produce H2O. So the net result is pure water. Ion exchange is not a redox process, as the charge on the ion doesn't change and its composition doesn't change. It is only its dancing partner that changes.

    Reverse-osmosis is essentially filtration at a molecular level. Water is forced at very high pressure through a membrane with pores sufficiently large to let water permeate, but not large enough to allow most ions to permeate. Because of their charge, ions have a larger diameter and may be repulsed by selective membranes. The permeate is pure, and the retentate contains a higher concentration of dissolved substances. A practical setup for homes is to use the pipe pressure to do the work, and collect the permeate at a slow rate. The retentate remains in the supply line and will still be fine for bathing, dishwashing etc. The rate at which RO works at these lower pressures allows only a few gallons a day to be purified, but that is usually more than enough for photographic and other home use. The guys who breed tropical fish in 200L tanks might need a larger system. Incidentally, that is also a good place to look for an affordable RO kit.

    All the processes to purify water are in one way or another energy, waste and/or cost intensive. In ion exchange, the two waste streams of acid and alkali used to condition the resins can be extensive. In RO, a lot of pumping energy is required to get the water through the membrane, and the membranes are expensive. In distillation, the latent heat of evaporation must be expended in the form of heating or vapour recompression, the latter being more energy (or rather, exergy) efficient. RO is best at removing everything including organics. Distillation is best at producing pathogen-free water, but cannot remove all organic volatiles. So for photographic use, I'd say RO is your best bet. Where I live, we pay ZAR 0,80 per liter. That is about $0,45 per 5 liters. It makes sense to use it for all photographic use other than washing, so I do not really ponder it much. I keep a 20 liter tank with a tap, and top it up with water from our local "fountain" where they fill 5L bottles for ZAR 4 a piece. Our local tap water is dodgy at times, and of course produces very significant drying marks. So the final rinse is always in purified water.
    Last edited by dorff; 05-09-2013 at 05:14 AM. Click to view previous post history.

  2. #12

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    Funny that you can't find distilled water in France. Here in Austria it is readily available and carries a label in both German (destilliertes Wasser) and Italian (acqua destillata). It's what I use for the final rinse with photoflo. Five liters is under 2 euros.

    De-ionized water, however, will be fine for your purposes as well. If that's all you can find, use it.

    Best,

    Doremus

  3. #13
    Ian Grant's Avatar
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    Distilled water is no better than De-ionised for photographic use and in most areas tap water's OK as well, - there's really only issues in hard water areas.

    Ian

  4. #14

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    Quote Originally Posted by Ian Grant View Post
    Distilled water is no better than De-ionised for photographic use and in most areas tap water's OK as well, - there's really only issues in hard water areas.

    Ian
    Anyone who's mixing XTOL stock using soft tap water of unknown iron content is asking for trouble. Mix XTOL stock using distilled (not "de-ionised," but "prepared using steam distillation") water. Store it in full glass bottles. Enjoy the benefits. See:


  5. #15
    Ian Grant's Avatar
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    Quote Originally Posted by Sal Santamaura View Post
    Anyone who's mixing XTOL stock using soft tap water of unknown iron content is asking for trouble. Mix XTOL stock using distilled (not "de-ionised," but "prepared using steam distillation") water. Store it in full glass bottles. Enjoy the benefits. See:
    I used Xtol and soft and hard tap waters for many years, replenished, from it's release until about 5 years ago, never had a problem. The issue is iron content of the water.

    Ian

  6. #16

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    Quote Originally Posted by Sal Santamaura View Post
    Anyone who's mixing XTOL stock using soft tap water of unknown iron content is asking for trouble. Mix XTOL stock using distilled (not "de-ionised," but "prepared using steam distillation") water...

    Quote Originally Posted by Ian Grant View Post
    I used Xtol and soft and hard tap waters for many years, replenished, from it's release until about 5 years ago, never had a problem. The issue is iron content of the water...
    Which is why I emphasized the unknown iron content of tap water, regardless of its hardness. Even if a single tap water sample is analyzed and iron found not to be a problem, variations throughout the year are inevitable.

    Just like the decision to use less of a particular developer stock solution than its manufacturer's specified minimum quantity, this is a "confidence or crap shoot" situation.

  7. #17
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    Quote Originally Posted by Sal Santamaura View Post
    Which is why I emphasized the unknown iron content of tap water, regardless of its hardness. Even if a single tap water sample is analyzed and iron found not to be a problem, variations throughout the year are inevitable.

    Just like the decision to use less of a particular developer stock solution than its manufacturer's specified minimum quantity, this is a "confidence or crap shoot" situation.

    While not disagreeing remember that Kodak themselves don't actually specifical recommend using Distilled or Deionised water with Xtol in their Data-sheet. Traces of Iron will cause severe problems with fixers where the Iron and Thiosulphate form a fast acting bleach. I have had minute Iron particles in water way back in the 70's long before Xtol.

    Ian

  8. #18
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    Every developer/stop/fix and many other photographic solutions I have ever made up, I have always used tap water. Never had a problem.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  9. #19

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    Quote Originally Posted by Ian Grant View Post
    While not disagreeing remember that Kodak themselves don't actually specifical recommend using Distilled or Deionised water with Xtol in their Data-sheet...
    In my opinion, Kodak's lawyers have been vastly more competent than its executive management over the course of recent decades. Adding an "avoid iron" recommendation to the XTOL data sheet would have opened the company to liability for all the "dreaded XTOL failure" losses incurred by users of the product. Much easier to blame (and discontinue) the one liter packages.

    Quote Originally Posted by Ian Grant View Post
    ...Traces of Iron will cause severe problems with fixers where the Iron and Thiosulphate form a fast acting bleach...
    I dilute TF-4 fixer stock with distilled water too.

    The advantage to our alkaline and rather hard tap water here is that it is very effective at washing. A final Photo-Flo film rinse gets mixed with distilled.

  10. #20

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    Quote Originally Posted by Ian Grant View Post
    While not disagreeing remember that Kodak themselves don't actually specifical recommend using Distilled or Deionised water with Xtol in their Data-sheet. Traces of Iron will cause severe problems with fixers where the Iron and Thiosulphate form a fast acting bleach. I have had minute Iron particles in water way back in the 70's long before Xtol.

    Ian
    Ian, Sal, this comes up occasionally with respect to mixing XTOL. What I've never understood is - XTOL contains an Iron sequestering agent. So why would a small amount of Iron in the water be a serious problem? I can see how it would be a problem with home-mix ascorbate developers, but it shouldn't be an issue with XTOL.

    Also - Sal - regarding steam distilled being better than deionized for XTOL, actually I recall Gerald Koch saying it could potentially be the other way around if the steam distilling apparatus introduces Iron into the water.

    Just thought I'd throw that extra wrench into the XTOL/water quality debacle.

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