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  1. #11

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    Quote Originally Posted by Gerald Koch
    Pyrocatechin and pyrocatechol are obsolete names for catechol. It is unfortunate that people still continue to use them as it is confusing.
    I find pyrocatechin in many contemporary scientific sources, not just in the popular literature, with the synonyms of pyrocatechol, catechol, oxyphenol, and even orthodioxybenzene. I allow that it is confusing that everybody does not use the term catechol, but from my perspective there seems to be as much precedent in the literature, including contemporary sources, for the use of pyrocatechin as for any of the other names by which this chemical is known, including catechol. Perhaps it would be best to always double reference the term, say catechol (pyrocatechin) or pyrocatechin (catechol).

    Sandy

  2. #12

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    Quote Originally Posted by srs5694
    There's Patrick Gainer's Q-P-TEA, published in the March/April 2004 issue of Photo Techniques (check the box labelled "CAT-P-TEA" and read the text):

    100 ml TEA
    0.2 g phenidone
    10 g hydroquinone

    Note that I've not used Q-P-TEA or any other staining developer; I'm just passing on what I've read.
    What I meant to write was that there are no commercially available staining developers based on hydroquinone. I am familiar with Pat's Q-P-TEA formula and have tested a few variations of it on my own.

    Sandy
    Last edited by sanking; 10-31-2005 at 10:54 AM. Click to view previous post history.

  3. #13
    Leon's Avatar
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    Quote Originally Posted by PhotoJim
    Pyrocatechin isn't nearly as popular but it is still out there. Sanking's well-known formula for Pyrocat-HD is probably the most common developer using pyrocatechin today,
    well ... there's DiXactol, Dixactol Ultra, Exactol Lux, Precyscol, Precyscol EF ... etc etc

    there are quite a few increasingly popular catechol based developers out there

  4. #14

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    Quote Originally Posted by sanking
    I find pyrocatechin in many contemporary scientific sources, not just in the popular literature, with the synonyms of pyrocatechol, catechol, oxyphenol, and even orthodioxybenzene. I allow that it is confusing that everybody does not use the term catechol, but from my perspective there seems to be as much precedent in the literature, including contemporary sources, for the use of pyrocatechin as for any of the other names by which this chemical is known, including catechol. Perhaps it would be best to always double reference the term, say catechol (pyrocatechin) or pyrocatechin (catechol).

    Sandy
    Catechol, being a substituted phenol, ends in "ol" as the chemical naming convention says it should. The three dihydroxy derivatives of benzine are thus catechol (1,2), resorcinol (1,3), and quinol (1,4). I concede it would be a very hard sell to get photographers to use the name quinol rather than hydroquinone.

    My reason for not liking the names pyrocatechol and pyrocatechin is that people confuse this compound with pyrogallol and pyrogallic acid.

  5. #15

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    I did not have much luck with this hydroquinone formula found on the net: 10g hydroquinone,1g ascorbic acid, 0.2g phenidone, TEA to 100ml.(Caution,risk present with hot TEA)

    Using the 1:25 dilution with Fortepan 400 film 9m 70F only a faint brown stain was visible when wet and when dry it was hard to see any stain at all.

    I'm not sure that hydroquinone can ever compare with pyro.

  6. #16
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    Gerald, I'm with you about name confusion. I am an avid tea drinker. Tea comes from an infusion of the leaves of the tea plant (Camellia sinensis or Camellia assamica), much like coffee comes from the beans of the coffee tree. When people take strawberry leaves and ginseng and make "tea" out of it, it drives me crazy. I have to ask for "real tea" and even then people have no idea what I mean.

    I'm kind of tempted to make a percolated or drip-filtered beverage out of ground something... maybe heat-treated gall nuts? So it will be ... pyrogallol coffee?

  7. #17

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    Quote Originally Posted by PhotoJim
    When people take strawberry leaves and ginseng and make "tea" out of it, it drives me crazy. I have to ask for "real tea" and even then people have no idea what I mean.
    The french use the term tisane. Definition: Any tea that is made with herbs other than true tea, is called a tisane. Wish other cultures made the distinction.

  8. #18
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    Quote Originally Posted by Alan Johnson
    I did not have much luck with this hydroquinone formula found on the net: 10g hydroquinone,1g ascorbic acid, 0.2g phenidone, TEA to 100ml.(Caution,risk present with hot TEA)

    Using the 1:25 dilution with Fortepan 400 film 9m 70F only a faint brown stain was visible when wet and when dry it was hard to see any stain at all.

    I'm not sure that hydroquinone can ever compare with pyro.
    I seldom use it that way myself. It seemed to be a little known fact that hydroquinone without sulfite could produce a stained image, so I threw it in. The colors of pyrogallol, catechol and quinol are different. In order to see the true color and density of the stain image, one may bleach out the silver with Farmer's reducer. Sometimes the silver image without the dye is not neutral. This effect is more used on paper than film.

    I don't know the Fortepan films. Even Pyrogallol stains different films differently.

    In any case, the QP-TEA may be used as the basis for a more conventional PQ developer by adding sulfite to the working solution. It works quite well with only sulfite as the activator in the manner of D-23. For a quick and dirty test, add 3 tbs of anhydrous sodium sulfite to a liter of 1+50 QP-TEA.
    Gadget Gainer

  9. #19

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    I like to make clear the developer I tried was not QP-TEA but had ascorbic acid in it.

    I did not see any reports about the stain density of QP-TEA yet.

  10. #20

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    Hi Jay,

    The test shots were headshots at EI 200 printed on grade 4 VC.For this developer the brown stain was very faint compared to the color of PMK pyro negs.

    It will be interesting if the results with QP-TEA stain get posted one of these days.

    Alan

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