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Thread: Pyrogallic acid

  1. #11

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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (c6h6o3 @ Nov 18 2002, 09:43 AM)</td></tr><tr><td id='QUOTE'>I was being conservative. The level of density he&#39;s talking about goes way beyond anything attributable to stain.

    BTW, I get more fog stain with Bergger than with HP5+. This is probably due to the longer development times.</td></tr></table><span id='postcolor'>
    I dont know, I was once playing with a pyro formula I found in a focal press book, and let me tell you the negatives could be used for arc welding. They were correctly exposed and developed to the suggested time and boy were they thick. After a few negs I was tired of trying to tame the formula so I stop playing with it, but adding sodium sulfite helped a lot. Thus my reasoning about David&#39;s problem. There are many variables that need to be accounted for like temperature, concentrations etc, to be able to really trouble shoot this problem.

    More stain with Bergger? .....hmm.....I am surprised...

  2. #12
    c6h6o3's Avatar
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    Admittedly there&#39;s something very strange going on with the stain I&#39;m getting. The last batch I developed were in pyro from the last little bit of stock solutions in my jars. The sulfite was about 2.5 months old, but it had been sitting in the bottom of the jar for about 1 month of that. Add to that the fact that I changed fixers for this batch, and all bets are off. The stain on BPF 200 looked just like what I used to get with HP5+ in PMK; leprechaun green.

    I plan to go back to Kodak Rapid fixer, mix up fresh pyro and then develop both HP5+ and Bergger. Then we shall see what we shall see. I&#39;ll keep you posted.
    Jim

  3. #13

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    I had nasty low contrast &#39;greening&#39; when solution B was too old. I wouldn&#39;t recommend using it if its older than a month.
    --Aaron
    art is about managing compromise

  4. #14

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    I use Hutchings recommendation and just add 0.4 grams to solution C before I am ready to develop.

  5. #15

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    I mix my PMK accurately, but find that my contrast is excessive with Hutchings&#39;s recommended time. Conclusion? Don&#39;t know, but the best you can do is use accurate amounts, then test. Fortunately PMK lasts for ages, so you only have to test occasionally. Pyrogallol is rather more variable than most tech grade chemicals. The idea that if some is good then more is better is going to give you some very hard negs.

  6. #16
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    Jorge-

    What do you add .4 grams of to solution C? My solution C was a little weak, as there wasn&#39;t quite as much left in the jar as of the other two, and I always put it in last.

    I wouldn&#39;t think that C would affect the stain that much anyway. Density yes, but it&#39;s the sulfite which affects stain the most and not the carbonate.

    Jim
    Jim

  7. #17

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    Sodium carbonate solutions should keep indefinitly if they are protected from the air. If not, it can absorb CO2 from the air and turn in to sodium bicarbonate.
    I have a theory that solution B slowly decomposes into a equilibrium mixture of sodium sulfide, sodium sulfite, and sodium sulfate.
    As many of you know sodium sulfide will fog film..

    --Aaron
    art is about managing compromise

  8. #18

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    Pyro, instead of making the sodium sulfite solution, I just add 0.4 grams of sodium sulfite to solution C. This way my sulfite is always fresh.

    Aaron you might be right I have not worked the redox reaction but sulfide is not far fetched. It could be an intermediate step in the oxidation of the sulfur ion into sulfate.




  9. #19
    c6h6o3's Avatar
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    Nice idea. I&#39;ll try it. Is that 0.4 gr for a one liter batch of working solution? (Don&#39;t make me do the math. It&#39;s too late in the day.)
    Jim

  10. #20
    c6h6o3's Avatar
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    Wait a minute. Now I&#39;m very confused. My Solution B stock is 105 gr / liter. Since I use 100 ml of stock/batch, that gives me 10.5 grams of sodium sulfite per liter of working solution. You&#39;re telling me to add 0.4 grams as a substitute for my Solution B stock? You can&#39;t be serious.
    Jim

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