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Thread: Water quality

  1. #61

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    Quote Originally Posted by gainer
    You do know, I'm sure, that if you want to remove the emulsion from its base in a hurry, you need onle immerse it in a Clorox solution. Chlorinated water is just slower.
    Well, chlorinated tap water will be about 1 mg/L free Cl2, Clorox is about 53,000 mg/L free chlorine. That's quite a difference!! And remember that the pH of the Chlorox is about 11.4 according to the MSDS. That's a pretty high pH - I'm sure that has a huge affect on the hardness/strength of an emulsion.

    I still think you are jumping to conclusions about the chorine in tap water. Especially if the water is sitting overnight, at 1 mg/L, reacting with your paper. So you have a 25 gallon tub, that's 100 litres of water, that 100 mg of chlorine. That's not much.

    Kirk

  2. #62
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    All I can say is do the experiment.
    Gadget Gainer

  3. #63
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    Quote Originally Posted by Ole
    That's not the problem. The problem is that cold water is saturated with calcium sulfate, it will precipitate as the temperature increases. Most other substances will dissolve as the temperatures go up, but gypsum will not.

    With the sulfite and thiosulfate we add to the wash water, the sulfate concentration in the wash will be high enough that it is a real problem if the water is hard. Both sulfite and thiosulfate will oxidise to sulfate, BTW.
    We have at least two uses for water. we use it to dissolve developing agents and we use it to wash developed and fixed materials. Sometimes we even bathe in it. I don't worry about calcium in the wash water. I don't even worry much about residual sulfate or thiosulfate since I read about findings that a little of that left in prints may make them last longer. The only reason I might have to boil water (other than to keep busy during childbirth) is for mixing developers.

    Magnesium sulfate is very soluble. Magnesium carbonate is not. Calcium sulfate carried in ground water, dripped from cave ceilings and reacted with CO2 is responsible for a good portion of what we see as stalagmites and stalactites. The carbonate is much less soluble than the sulfate for both magnesium and carbonate. You could clear most of the calcium and magnesium out of hard water by bubbling CO2 through it. What is left to combine with the sulfate ions? If there is enough heat, you may evolve SO2. I don't know. But I do know that heating hard water in the presence of air leaves a precipitate. I doubt that you have free sulfate or sulfite ions. Sulfurous acid with heat gives of SO2 and leaves water behind or sends it off as steam. I have forgotten why we were being so scrupulous about this. Hav we come across some ruined photos by past photographic geniuses who did not know all this chemistry?
    Gadget Gainer

  4. #64
    Ole
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    Quote Originally Posted by gainer
    ... You could clear most of the calcium and magnesium out of hard water by bubbling CO2 through it...
    Bubble MORE CO2 through it, and the solids dissolve again as the pH rises from increased H2CO3 (CO2 + H2O). Some stalagtites are formed by CO2 escaoing from the water, giving a drop in the pH whick leads to CaCO3 precipitating.

    It ain't always easy...

    Quote Originally Posted by gainer
    I have forgotten why we were being so scrupulous about this. Hav we come across some ruined photos by past photographic geniuses who did not know all this chemistry?
    I have no answer for that question!
    -- Ole Tjugen, Luddite Elitist
    Norway

  5. #65
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    Quote Originally Posted by gainer
    I have forgotten why we were being so scrupulous about this. Hav we come across some ruined photos by past photographic geniuses who did not know all this chemistry?
    My 2 cents worth: I live in an area where the water is hard (dissolved limestone). I used to be scrupulous about using filtered water (Brita filter jug, I think this is activated carbon), but when I went to a 15-ilter tank line for film processing, laziness got the better of me and I used straight tap water. I have seen no difference. I finish all sizes of film by putting a few mil of washing agent in the final wash water (tap water). The amount needs to be such that there is a unbroken film of water on the photographic film when you lift it out of the water, too much and suds will form. I virtually never experience drying marks. I take care to hang the film slightly off the perpendicular so that water drains to the edges.
    The only time I have had problems with water is with print toners that involve bleaching - using tap water has resulted in a definite powdery deposit on the prints.

    Regards,

    David

  6. #66

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    I've had a terrible time with tiny particles on my negs. I now use distilled water for the dev and the final rinse, but even at 8x enlargment there are some white spots in the print. My early negs are so bad I had to scan them in the end.

    The distilled water costs are killing me (£3.50 for 5L), and I can't find it anywhere else. Going to try the supermarket bottled water instead.

    The only thing saving my prints right now is I never enlarge 8x from 6x7 negs but I've had to pretty much ditch 35mm since I cannot get a clean 8x10 print.

    Any advice would be great!

  7. #67
    David H. Bebbington's Avatar
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    Quote Originally Posted by m_liddell
    I've had a terrible time with tiny particles on my negs. I now use distilled water for the dev and the final rinse, but even at 8x enlargment there are some white spots in the print. My early negs are so bad I had to scan them in the end.

    The distilled water costs are killing me (£3.50 for 5L), and I can't find it anywhere else. Going to try the supermarket bottled water instead.

    The only thing saving my prints right now is I never enlarge 8x from 6x7 negs but I've had to pretty much ditch 35mm since I cannot get a clean 8x10 print.

    Any advice would be great!
    I would bet the spots are caused by rust particles from your water pipe. Paterson and others sell a filter which you can fit to your tap/faucet. I would think this will fix the problem, maybe in conjunction with a Brita filter jug. I think distilled water is overkill!

    Regards,

    David

  8. #68

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    Quote Originally Posted by gainer
    What is left to combine with the sulfate ions? If there is enough heat, you may evolve SO2. I don't know. But I do know that heating hard water in the presence of air leaves a precipitate. I doubt that you have free sulfate or sulfite ions. Sulfurous acid with heat gives of SO2 and leaves water behind or sends it off as steam.
    Partick, CO2 dissolved into water will form H2CO3, carbonic acid. When this reacts with your Ca and Mg sulfates, it will precipitate out the carbonates, but it leaves the acid of the sulfate. That is sulfuric acid, not sulfurous acid. It's simple stoichiometry. (I don't get to use that phrase too often.) If you really boil that down, you will release sulfur trioxide, not SO2. But anyway, as you say, this is getting far away from the original, mutated thread.

  9. #69

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    Quote Originally Posted by m_liddell
    I've had a terrible time with tiny particles on my negs.
    [...] Any advice would be great!
    Have you tried an inline water filter? Perhaps your problem is not with mineral deposits but with particulates in the water.

    For wash water you only need a low temperature filter (these often have a blue plastic housing), and you can find them for pretty cheap. Get a 20 micron filter for it.

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