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  1. #11
    Photo Engineer's Avatar
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    Michel;

    Pyro is by far more toxic than HQ. Look at Anchell and Troop for their comment.

    They say that pyro and its derivatives are among the most toxic chemicals used in the darkroom.

    PE

  2. #12
    skahde's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    They say that pyro and its derivatives are among the most toxic chemicals used in the darkroom.
    Just one question: What source or citation do Anchell and Troop give for their statement? What source or citation one could crosscheck do they give anywhere anyway?

    best

    Stefan

  3. #13

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    Pyrogallol was used as to treat a skin disorder here (Australia) for many years. One patient did succumb to cancer after using it thickly on the whole back of his hands every day for something like 20 years (iirc). It's not used anymore for this purpose. Reasonable care in the darkroom makes it not a concern.

    Hydroquinone is reputed to be bad in effluent because it affects marine life.

  4. #14
    Ian Grant's Avatar
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    Stefan, all commercial chemicals have MSDS (US) or COHSS (EU) data sheets and even before these two systems data was published about the toxicity of these chemicals.

    The toxicity of various photographic chemicals has been known about for a considerable period of time, and as such authors like Anchell & Troop would have access to a wide variety of sources. However they were not publishing a scientific or academic paper so had no call to cite sources.

    Ian

  5. #15
    skahde's Avatar
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    Quote Originally Posted by Ian Grant View Post
    [...] as such authors like Anchell & Troop would have access to a wide variety of sources.
    Question is why didn't they check them? Hydroquionone and Pyrogallol have more or less identical toxicity and cancerogenicity if you have a look at the MSDS.
    Quote Originally Posted by Ian Grant View Post
    However they were not publishing a scientific or academic paper so had no call to cite sources.
    They certainly were not obligated to give a proof but in this case they were not able to give one in the first place as their statment is plain wrong. There is quite a number of rather bold statements in the photographic literature where there is no kind of proof given but which are in contradiction to well documented work others did. My personal conclusion is to rather ask for proof than taking for granted that some highly regarded source may not give false information in one place or another (and they inevitably do!).

    At the end of the day it is our negatives, prints or even health which may take harm or your time and money wasted and in such a situation it's IMHO not clever to just rely on someone elses word.

    best

    Stefan
    Last edited by skahde; 10-30-2007 at 07:28 AM. Click to view previous post history.

  6. #16

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    Skin whitener? Michael Jackson?

  7. #17
    Ian Grant's Avatar
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    Stefan, as someone who has worked with chemicals almost all my working life I don't take everything in MSDS/COHSS data as gospel.

    It is normal lab practice to treat all chemicals with respect, and a few with extreme care, in my case that was cyanides and Hydrofluoric acid.

    Its up to you to read for yourself and decide how you handle chemicals. Photographers found from experience that Pyrogallol was more toxic than Hydroquinone not through a few experiments with lab rats.

    What you are calling rash statements are just accumulated knowledge built up over a number of years. But you would find the same information coming from very different origins. LP Clerc's data came predominantly from Europe and French photographic companies, while Kodak's came from the US and the UK.

    We don't need to read the original papers and sources because history has informed us how to safely use these chemicals in our photographic practice.

    Ian

  8. #18
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    Quote Originally Posted by Ian Grant View Post
    Stefan, as someone who has worked with chemicals almost all my working life I don't take everything in MSDS/COHSS data as gospel.
    At some point writing MSDS was part of my job and I therefore know there limitations very well.
    Quote Originally Posted by Ian Grant View Post
    Photographers found from experience that Pyrogallol was more toxic than Hydroquinone not through a few experiments with lab rats.
    But what kind of experience? Described where? Observed and confirmed by who? As long as there is no kind of evidence given I'd rather trust the rats.

    Quote Originally Posted by Ian Grant View Post
    What you are calling rash statements are just accumulated knowledge built up over a number of years.
    Have a look at eg. Richard Henry "Controls in Black and White Photographie" and see how much of that "accumulated knowledge" turns out to be well ripened myth when really put to the test.

    Quote Originally Posted by Ian Grant View Post
    We don't need to read the original papers and sources because history has informed us how to safely use these chemicals in our photographic practice.

    Ian
    No, I don't think knowledge does accumulate. In my view it is lost over time once it has been established. What you describe is a situation where nobody refers to the original papers anymore but information taken from them goes from ear to mouth into publications, out again taking another round, loosing shape and contents to a degree where the original statment is hard to be recognised or lost alltogether.
    As a result, there is lots of "wisdom" around which has little to do with what was meant but lots of procedures are in use which obviously work but there is little in-depth knowledge around why and in some cases why not. That is where we are: Photography is as much science as it is craft.

    But coming from the craft-side one shouldn't pretend to do any kind of science or make statments beyond that somethings "works" within the craft. There are clear rules how to part assumption and myth from knowledge (as limited as it might be) build up over times much longer than photography exists. Not sticking to them is a weekness often accepted by authors for a reason: Emperors new cloth.

    best

    Stefan

  9. #19
    Willie Jan's Avatar
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    If you know how many photographic used chemicals are in our food, you will stop eating.

  10. #20
    Ian Grant's Avatar
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    Stefan, a simple Google search brings up plenty of material on the relative toxicity of Hydroquinone and Pyrogallol.

    One line in "Environmental Goitrogenesis" - By Eduardo Gaitan states "Hydroquinone and Pyrogallol may cause discoloration of the skin, and Pyrogallol even death after topical application. This is a scientific publication with plenty of references to other sources.

    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.

    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.

    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. The smaller scale use is far less of a problem, in comparison top commercial darkroom & their workers exposed to Pyrogallol throughout the whole of each working day a century ago.

    If you choose to ignore scientific facts, published widely and freely available that's up to you. The evidence is there if you look for it.

    Ian

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