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  1. #21

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    Taking another course from the original question, if the toxicity of hydroquinone is a concern, you might want to investigate using ascorbic acid, or one of its variants, instead. You can usually achieve similar results with ascorbic acid, although you'll need to adjust quantities of various ingredients, particularly if you use ascorbic acid rather than sodium ascorbate. (Note that "similar" doesn't mean "identical;" if you're very picky about your developers you may find the subtle differences unacceptable.) APUG members Ryuji Suzuki and Pat Gainer have both published several popular formulas that use ascorbic acid, and a few commercial products use it, too (Kodak XTOL, Agfa Neutol Plus, and Silvergrain Tektol spring to mind).

  2. #22
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    All of this furor claiming that A&T gave no reference.

    Well, if you read A&T, you would find that they DID give a reference. It is a citation by Gordon Hutchings who said that "They may be the most toxic chemicals in the darkroom". I would personally amend that to say "second to selenium".

    None of the above are severly toxic if, as Ian has pointed out, you observe safe handling procedures in mixing, use and disposal.

    PE

  3. #23
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    In extensive tests by Kodak, HQ and Metol and several color developing agents (CD-3, CD-4 and CD-6) were found to be low in toxicity as they are not absorbed through the skin to any great extent. This reduces toxic reactions from contact.

    Other developing agents can be readily absorbed through the skin.

    All of them are toxic to some degree or another if you injest them.

    PE

  4. #24
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    Quote Originally Posted by Ian Grant View Post
    Stefan, a simple Google search brings up plenty of material on the relative toxicity of Hydroquinone and Pyrogallol.
    Thank you for taking the time and doing a search. I couldn't agree more that Hydroquinone as well as pyrogallol should both be treated with care and will both cause serious problems if not used in line with appropriate caution.

    My point is the difference between pyro and hydroquinone and as far as I can your search still didn't turn up anything demostrating any large difference in toxicity or cancerogenicity.

    Quote Originally Posted by Ian Grant View Post
    Another states "PYROGALLIC ACID (pyrogallol, 1,2,3-trihydroxybenzene). Pyrogallol is highly toxic by every route of exposure and can also readily be absorbed through the skin. It then goes on to list the problems.
    If you extend your search a bit you will find that hydroquinone is also readily absorbed through the skin. Maybe to a lower rate, I don't know. But I would check if wanted to know. Or if I would care if pyro is an extraordinary risk compared to other developing agents which are in regular use or if wanted to write down such a statement in a book.

    Quote Originally Posted by Ian Grant View Post
    There is plenty of documented evidence again in scientific publication, looking into the causes of sickness in darkroom workers, and the word Pyrogallol features in them all as being by far the most toxic of the developing agents.
    Sounds like interesting reading. I'm sure you could reference it. And you take it for granted that Hydroquinone is much better?

    Quote Originally Posted by Ian Grant View Post
    So Anchell & Troop aren't printing myths, it's one of the reasons why photographers and more particularly manufacturers like Kodak, Ilford & Agfa moved away from using Pyro based developers.
    They moved away from pyro because hydroquinone was more convenient to use, gave better, more consistent results and was also cheaper.

    Do a search for the risks connected with the regular exposition to hydroquinone and it will be equally long showing a different but in no way better picture.

    If you check the facts and don't rely on 3rd, 4th, 5th generation literature there is little difference between pyro and hydroquinone with respect to the safety you should apply when using them and the risk connected with their use.

    best

    Stefan

  5. #25
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    The LD50 of Pyrogallol is very low. Due to a lack of volunteers (Gordon's words), there is no exact human data but he does publish an estimated LD50 for humans from known cases of lethal poisoning by pyro. It is apparently very low when compared to HQ.

    PE

  6. #26
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    Quote Originally Posted by Photo Engineer View Post
    In extensive tests by Kodak, HQ and Metol and several color developing agents (CD-3, CD-4 and CD-6) were found to be low in toxicity as they are not absorbed through the skin to any great extent.
    Unfortunately hydroquinone is also readily absorbed through the skin.

    I hope Gordon Hutchings is doing fine and I will take this as good enough evidence that one can use pyro as well as hydroquinone on a regular basis and stay healthy as long as you take enough care.

    best

    Stefan

  7. #27
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    Stefan, can you not read Hydroquinone is not readily absorbed through the skin, as Ron (PE) says and also the information I posted. HQ is relatively harmless, Pyrogallol positively dangerous by absorption.

    Ian

  8. #28
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    I have to agree 100% with Ian! (and Gordon Hutchings and A&T and Kodak's medical department and many published reports)

    PE

  9. #29

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    On the subject of Anchell and Troop's level of warning on chemicals, I have collected some posts by Bill Troop about the VMI mercury intensifier because a have a set of negatives that would benefit from that type of intensification. In his posts, he warns that mercuric chloride is "caustic" and needs to he handled with care.

    Now, as much as I very much admire the author's work and efforts to be helpful, I find it extraordinary that he should not issue warnings about the danger of mercury compounds and the need to dispose of them responsibly. I get the impression that he feels very competent in his own use of such chemicals (as do I), but he is remiss in not being more thorough at least in this case.

    On the subject of hydroquinone, at least it degrades in the environment, and is safe enough to be used with normal precautions.

  10. #30
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    I know that Bill is very aware environmentally. I think perhaps that since the problems with mercury are so well known that he may have not gone into any detail compared with his comments about pyro for example.

    In any event, you cannot be all things to all people.

    PE

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