Why Pyrol rather than hydroquinone?

Discussion in 'B&W: Film, Paper, Chemistry' started by Canuck, Jun 6, 2005.

  1. Canuck

    Canuck Member

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    Just started into the mixing up my own staining developers. I found a lots of formula dealing with pyrol and catechol but almost nothing with hydroquinone. Did some research on the great wide net but not much in the way of hits (maybe looking in the wrong places) for a staining developer based on hydroquinone. I am not wanting to rehash the old news of staining versus regular developers, but why most formulas have chosen to use pyrol or catechol rather than hydroquinone. Is there a major advantage with grain, accutance, and tone with pyrol or catechol over hydroquinone? I just mixed up a hydroquinone developer (formula from another thread here), so not committed 100% yet to it and just doing more research before ordering more chemicals to play with.

    Elvis
     
  2. psvensson

    psvensson Member

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    I think the reason is that hq won't stain if there's more than a minute amount of sulfite in the developer, and sulfite is the traditional preservative of choice. There are ways of getting around this, of course. As Gainer has shown, you can use an organic solvent instead of water for the stock solution. The other way is to mix the developer from powder right before use. I did this with good results. Hq dissolves quickly in water.
     
  3. Canuck

    Canuck Member

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    Sounds interesting. I don't recall sulfite as I have it as a two parter and I mixed it up a couple of weeks ago. Developed with it just a couple of times so far. Count is 5 good sheets, to one badly streaked one.
     
  4. psvensson

    psvensson Member

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    Is this the one modified from Pyrocat by Mehment Kismet? It contains a small amount of bisulfite, which produces sulfite ions. The amount is so small that it won't prevent stain, but neither will it do much to preserve the stock solution, I think. I imagine the keeping qualities could be pretty good anyway.
     
  5. Canuck

    Canuck Member

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    I think that's the one. It looked like a good one to try since I had all the necessary chems on hand.
     
  6. psvensson

    psvensson Member

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    I'm tempted to try it myself. BTW, I neglected to mention that the reason it contains sulfite ions is that these are necessary to activate the hq-phenidone synergy. Without them, the developer would be a lot slower.

    Are you getting a lot of stain?
     
  7. Canuck

    Canuck Member

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    Its seems to be working well. Lots of brownish coloured staining. Only bad sheet I got had some nasty streaks of brown on it. Until now, the last few sheets looked fine. Using APX100 at EI=50 @ 8 minutes.
     
  8. avandesande

    avandesande Member

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    hydroquinone only has two phenolic sites on it vs 3. hydroquinone does not crosslink with the gelatine as readily as pyrogallol or pyrocatechol. Crosslinking is what chemically binds the pyrogallol to the gelatine causing stain.
     
  9. Canuck

    Canuck Member

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    So can I assume that it is due to this that the speed of development is slower that using pyro or catechol? I have lots of staining on my negs so the staining isn't an issue but I guess the development time and the amount HQ used maybe.
     
  10. avandesande

    avandesande Member

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    HQ does oxidize more slowly than pyrogallol/catechol so this would probably explain the slower speed. It also has a better shelf life for the same reason.

    Crosslinking is why pyrogallol is used to tan leather. It actually chemically binds the protein strands together which make them tougher and harder.
     
  11. Tom Hoskinson

    Tom Hoskinson Member

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    Hydroquinone (1,4-Dihydroxybenzene);
    Catechol (1,2-Dihydroxybenzene);
    Pyrogallol (1,2,3-Trihydroybenzene).

    All three of these Benzine Ring compounds have the potential to act as tanning and staining developers. Sulfites can depress or stop the tanning and staining with all three.

    Pyrogallol is the most active of the three. Catechol is less active than Pyrogallol and more active than Hydroquinone. In general, it is possible to substitute one of these reagents for another, taking into account the differences in activity.

    All three developers become more active in the presence of sulfite - but with addition of too much sulfite lose their ability to stain and tan.

    All three developers are additive (show increased activity) or are superadditive with phenidone and phenidone derivatives.

    All three developers are additive with Metol.

    All three developers are additive (or superadditive) with ascorbic acid.
     
  12. avandesande

    avandesande Member

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    It is probably a difference in activity (proportional stain) between pyrogallol and HQ of at least a factor of 4 if not more. So yes, technically it stains but not in a useful sense.
    Any of these developer solutions will turn colors and fog the negative. This in not what people are looking for.
     
  13. psvensson

    psvensson Member

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    Gainer's staining developer gets good reviews from other people. I tried it and did not see a lot of fog. I bleached it out to see the stain. It did not appear very strong, but I haven't tried any pyrogallol or catechol developers.
     
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  15. Canuck

    Canuck Member

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    I haven't tried the Gainer formula (yet) but one thing I have noticed is that fog level is visually higher with the HQ developer than what I get with developing in say Rodinal. What can be done to reduce fog level? Addition of KBr?
     
    Last edited by a moderator: Jun 6, 2005
  16. psvensson

    psvensson Member

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    Gainer's developer uses TEA rather than carbonate as the activator, so it has a lower pH that may mean less fog. Metaborate could also work.
     
  17. Tom Hoskinson

    Tom Hoskinson Member

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    In my direct experience, Hydroquinone based staining and tanning developers produce useful stain and proportional tanning with low fog.
     
  18. Canuck

    Canuck Member

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    Next experiment I'll try borax. Since borax is less basic, does that mean my development times needs to be increased?
     
  19. Mehmet Kismet

    Mehmet Kismet Member

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    Hi,

    I am using since long time, the formula below and the result is what I expect from that kind of developer. The only reason why I am using hydroquinone instead of catechol is very simple because it is difficult if not impossible to have catechol in Turkey.
    The keeping properties are excellent, and I think that it is worth to give a try.

    Here is the formulae.

    Best
    Mehmet Kismet

    A:
    Distilled water : 400cc
    Sodium Bisülfite 5g
    Hydroquinone 25g
    Phenidone 1g
    (dissolved in5cc
    isopropyl alcohol)
    Pot. Bromide 1g
    Water to make 500cc

    B
    Distilled water 1000cc
    Sod. Carbonate 200g
    (anhydre)

    Some data for 4"x5" FP4(EI 64) with JOBO CPP-2 and 3010 drums with rotating speed @P
    (N)
    10A + 50B + 750Water
    8min.@22oC

    (N+2)
    15A + 75B + 750Water
    6,5min. @22oC
     
  20. psvensson

    psvensson Member

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    You're going to need a lot of borax to get your times close to what you get with carbonate. I wouldn't go there.
     
  21. Canuck

    Canuck Member

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    Hmmm ... more time in the darkroom and this is bad how? :D
     
  22. Ole

    Ole Moderator Staff Member Moderator

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    One of the really interesting things about these developers is that 1,3-Dihydroxybenzene - isn't. A developer, that is. Utterly useless for all developing purposes.
     
  23. dancqu

    dancqu Member

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    You're in a hurry. Mr. Canuck wishes to go where no man
    has gone before then return and tell us of his findings.

    I will suggest he give a bicarbonate-carbonate blend a try;
    perhaps a 50/50 blend by weight for starters. Dan
     
  24. NER

    NER Member

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    Hydroquinone is not a staining developer. It exerts a tanning effect, and has been reported to tan (crosslink) more efficiently than pyrogallol or pyrocatechin [A. & L. Lumiere, B.J. Phot., 285 (1906), and A. G. Tull, J. Phot. Sci. 11 (1963)]. Hydroquionone has less reducing power than pyrogallol because of differences in physico-chemical properties, e.g., redox and bromide potentials. See John & Field, "Photographic Chemistry," 1963, and G. Haist, "Modern Photographic Processing," 1979.
     
  25. Tom Hoskinson

    Tom Hoskinson Member

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    Sorry, NER but you are wrong. Hydroquinine (1,4-Dihydroxybenzene) is a staining developer and has been documented as such by many researchers - Including Grant Haist.

    In addition, I have a substantial amount of sensitometric data of my own that confirms this.
     
  26. NER

    NER Member

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    Give me a citation - or publish.