PyrocatMC stock turned light brown

Discussion in 'B&W: Film, Paper, Chemistry' started by Cor, Feb 22, 2008.

  1. Cor

    Cor Member

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    I hijacked below message from another thread, I have a similair (I think) experience. One year ago I mixed a small batch of PyrocatMC in glycol. Since I had quite some PyrocatHD, I did use the MC stock again only last week, The stock had turned lightbrown. Is this normal? I did process some film with it, these seem to be ok, although one sheet was a bit thin, but that might have been an exposure issue,

    Thanks,

    Cor

     
  2. sanking

    sanking Member

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    This is normal. The MC stock A solution will turn brown, or sometimes red, after a few months of storage. This does not affects its developing characteristics. I don't know why the color changes with MC. Pat Gainer suggested, or so I recall, that some of the changes we see in mixing solutions in glycol is from food dyes.

    Pyrocat-HD mixed in glycol remains very clear, even a year or more after mixing.

    Sandy King
     
  3. Cor

    Cor Member

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    Thanks for the fast feed back and the peace of mind! Although my negatives were alright , was a bit worried about the colour change! (esp. as you say that PyrocatHD stays very clear in glycol)

    Thanks again & best,

    Cor
     
    Last edited by a moderator: Feb 22, 2008
  4. gainer

    gainer Subscriber

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    I think oxidation of a very small amount of pyrocatechin will cause a lot of color. The same goes for the paraminophenol of Rodinal, which after years of storage is quite potent, but also quite dark. You could dissolve a pinch of pyrocatechin in a liter of water and watch the color change over time. Hydroquinone will do the same. Metol is also quite colorful. If there is any doubt you can do a simple snip test with a piece of exposed film. Even if you don't use 35 mm, you could keep a roll on hand for such tests. If you do a snip test when the developer is new, you will have a sample to compare with later tests.
     
  5. Snapshot

    Snapshot Member

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    I've had some of my pyro-metol TEA formula turn a light green with time. There is no loss of potency or development action that I can see.
     
  6. john_s

    john_s Subscriber

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    p-Aminophenol was used in hair dye, as was pyrogallol. The former is banned in Europe now for this purpose.
     
  7. vet173

    vet173 Member

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    I have had some Pcat-P for about 8 mo, about 200 left out of 1000ml container . Mixed with tap water. ( you can get away with that in the northwest ) It is a little brown, but still works OK. I did notice last time that it did not turn quite as dark with the purple. It will take on an amber color after a little while which is normal. I have used the developer after letting it set for almost an hour and still worked OK. Not a recommendation though.