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  1. #11
    roy
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    Quote Originally Posted by m_liddell
    I don't think there is anywhere else in the UK that sells it
    I bought mine from Photographers Formulary in the USA. No problems with the order and sent without delay in chemical packets so very light in weight for postage. Just add water - no problems.
    Roy Groombridge.

    Cogito, ergo sum.
    (Descartes)

  2. #12

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    Quote Originally Posted by Leon
    yes - pyrocat is short for pyrocatechol is it not ....? Definitely never seen a recipe for sandy's P'cat HD with pyrogallol in it.
    Those who point out that the formula for Pyrocat-HD has never contained pyrogallol are of course correct. I have made a few modifications over the years to the formula but the main reducer has always been pyrocatechin/pyrocatechol/catechol. Some of the accepted modifications I have myself used and/or described are the following.

    1. Substitution of metol for phenidone at the rate of about 10-20 parts metol to one part phenidone. This formula gives slightly better acutance with rotary processing, but slightly lower effective film speed.

    2. Substitution of a 20% solution of sodium carbonate for the 75% solution of potassium carbonate. This requires changing the normal dilution from 1:1:100 to about 1:5:100, or 2:2:100 to 2:10:100. Some have also substituted sodium hydroxide for carbonate (see my article at Unblinkingeye. com) and this works fine also, though I think it gives slightly larger grain.

    3. The addition of a very small amount of ascorbic acid (about 1ml of a 1% solution of ascorbic acid per liter of working solution). This bumps the energy of the developer up considerably without otherwise changing the characteristics of the developer. However, more than this kills the stain.

    4. Changing the formula from sodium bisulfite to sodium metabisulfite since, as it turns out, most sodium metabisulfite is metabisulfite anyway.

    5. The addition of EDTA (Trisodium variety) in amount of about 5 g per liter of stock solution as a chelating agent. Suggested only for those who mix their working solution with tap water of unknown quality.

    6. Use of slightly more of Stock A than Stock B in the working solution when developing film for very long periods of time, as might be necessary for example when developing a low contrast film like JandC 400 exposed in a flat lighting situation. Instead of a 2:2:100 dilution I would now recommend a 3:2:100 or 5:3:100 dilution which will cut down slightly on B+F. I also recommend the asymmetrical solution for semi-stand and extreme minimal agitation where development times are very long. Say, instead of 1:1:150 use 1.5:1:150, or 3:2:300, or 5:3:300.

    I have also experimented with the addition of more sulfite (you already get some from the sodium metabisulfite). The additional sulfite will make the formula much more energetic but kills the stain so I don't recommend this except for people who don't want the stain.

    It is very true, as someone mentioned in a previous message, that changes in developer formulas almost always come at some cost, i.e. you can decrease grain but at the cost of acutance, or you can increase acutance at the expense of grain. Pyrocat-HD has a slight advantage in this regard because the grain masking that one gets with the stain it allows for much finer grain than if there were no stain. People are free to tinker with the Pyrocat-HD formula and use it as they will, and if that results in an improvement for their purpose, more power to them. I do a lot of tinkering myself, and indeed make modifications for specific purposes, but if I knew a way to significantly improve the formula in terms of its overall versatility, which is one of the truly great virtues of this developer, IMO, I would have already made that information available.



    Sandy
    Last edited by sanking; 02-15-2005 at 08:08 PM. Click to view previous post history.

  3. #13

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    I will pass a copy of the thread to Brian Walker at the Blackthorn Centre for his comments. This will take a few days as he is away at the moment. Personally I know nothing about the developer, I merely look after the web site.

    I do know that he and the late Barry Thornton carried out a considerable amount of research into the developer. I do know version that they use at the Blackthorn is modified from the original and they did debate whether to use the Pyrocat-HD name as it differs quite a bit.

  4. #14
    Bruce Osgood's Avatar
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    Pre Tinkering

    Quote Originally Posted by sanking
    Those who point out that the formula for Pyrocat-HD has never contained pyrogallol are of course correct.
    (LARGE SNIP)

    (END SNIP)
    IMO, I would have already made that information available.

    Sandy
    So, where do we stand today in regards to to PYROCAT-HD? Is the formula published at Unblinking Eye the 'basic' formula from which all others have been derived? Or is there a published formula that has superseded the Unblinking Eye (maybe the eye blinked?) formula and considered 'generic'?

    For the person who has never used Pyrocat-HD, what is the current, basic formula.... and where can it be found.

  5. #15

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    Quote Originally Posted by Bruce (Camclicker)
    So, where do we stand today in regards to to PYROCAT-HD? Is the formula published at Unblinking Eye the 'basic' formula from which all others have been derived? Or is there a published formula that has superseded the Unblinking Eye (maybe the eye blinked?) formula and considered 'generic'?

    For the person who has never used Pyrocat-HD, what is the current, basic formula.... and where can it be found.
    The original formula was first published at www.unblinkingeye.com, and all subsequent modifcations to the formula made by me were posted to that site. Therefore, if there is such a thing as an official Pyrocat-HD formula it is the one you will find at Unblinkingeye.

    Even though I never exchanged any communicaitons with him on the subject I had long suspected that there was a strong family ressemblance between some of Barry Thornton's last developers, particulary Exactol, and Pyrocat-HD. One could easily see why, in that Exactol, like Pyrocat-HD, is based on pyrocatechin/phenidone and the recommended dilution for silver printing is 1:1:100 for both developers. Now that we know that Barry Thornton carried out a considerable amount of research into the Blackthorn modified Pyrocat-HD developer it seems quite reasonable to speculate that Exactol is to some degree derived from Pyrocat-HD, with modifications perhaps made by Thornton to lower the working pH. If Exactol ever gets back on the market I will perhaps try to obtain some and do a comparison of it with Pyrocat-HD.

    Sandy
    Last edited by sanking; 02-16-2005 at 08:26 PM. Click to view previous post history.

  6. #16
    Bruce Osgood's Avatar
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    Quote Originally Posted by sanking
    Therefore, if there is such a thing as an official Pyrocat-HD formula it is the one you will find at Unblinkingeye.

    Sandy
    Thank you, that's what I hoped was the answer.

  7. #17

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    Sandy,

    I think Exactol Lux is available again and so is Presysol (cannot remember spelling) which sounds similar. Website is:

    www.monochromephotography.com

    Personaly the first obvious difference with exactol Lux is a little more speed than pyrocat....I think....

    Tom

  8. #18

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    Quote Originally Posted by Tom Stanworth
    Sandy,

    I think Exactol Lux is available again and so is Presysol (cannot remember spelling) which sounds similar. Website is:

    www.monochromephotography.com

    Personaly the first obvious difference with exactol Lux is a little more speed than pyrocat....I think....

    Tom
    Thanks for the information. I will look into this.

    You may be right about the speed difference. However, comparing the EFS of different developers is one of the most difficult characteristics to compare. You really need to do this with some kind of sensitometric control procedures. In-camera methods are inherently faulty due to the lack of exposure precision in our systems. Plus, for the comparison to be valid you must develop the comparison negatives to the exact same CI, and unless you plot the curves it is difficult or impossible to know for certain when this has been achieved.

    Sandy

  9. #19

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    Back to the original question, has anyone used the "modified" pyrocat-hd?

  10. #20

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    Maybe the question should be: Has anyone done any controlled comparative testing between Sandy King's original formulation and this variant-modification?

    Some of us in the USA and elsewhere who use Sandy's original Pyrocat-HD formulation (and/or its public domain variations) are curious.
    Tom Hoskinson
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