PC-TEA: Fighting the fog...

Discussion in 'B&W: Film, Paper, Chemistry' started by aldevo, Feb 8, 2005.

  1. aldevo

    aldevo Member

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    I'm new to the world of PC-TEA. My initial tests suggest that where grain, accutance and tonality are concerned it certainly lives up to expectations.

    However, during my first darkroom session I noticed that my printing times were taking quite a bit longer than necessary. Having saved my film leader I took a look at it and, you betcha, quite a bit of fog.

    So I did a bit of searching and found that Sandy King recommended on APUG that users of PC-TEA consider mixing a solution of 1% BZT and adding 1 ml of this solution per sheet or roll.

    I painstakingly weighed out 10g of BZT and dissolved it in solution to give 1L of 1% BZT. I used a digital scale for this step (don't even try to use volumetric measurements for BZT as its in the form of needle-like crystals which means its bulk density is all over the place depending on whether its "fluffed" or "packed") because I am aware that too much restrainer is a bad thing.

    On the next roll I used 1 ml of this solution for 350 ml of developer working solution prepared with 7 ml of PC-TEA concentrate. I developed 24 exposures of Tri-X at 68 degrees for 9 minutes. Voila, the fog was gone!

    And so was most of my image! Massive speed loss and extreme contraction were the result!

    I'm sort of at a loss to explain this...could it be because the 1 ml of solution is intended for processing of sheet film (Sandy does sheet films mostly) and that requires far more working solution?

    Better yet, anybody have a recommendation for a BZT solution that doesn't throw the baby (image) out with the bathwater? (fog)
     
  2. fhovie

    fhovie Subscriber

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    I use about 1g / liter potassium bromide - works great
     
  3. aldevo

    aldevo Member

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    I'm using 400TX in 35mm. I've compared the discarded ends of the film (yup, I save them!) from my PC-TEA processed film vs ones processed in FG7 and Rodinal and there is a definite increase in fog using PC-TEA.

    I've made that determination by viewing these film ends in front of an unfrosted 150W bulb. The difference in how bright the filament appears is pronounced.
     
  4. Tom Hoskinson

    Tom Hoskinson Member

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    Take some of your 1% BZT solution and dilute it to make an 0.1% solution. Then, in your working developer, try using 10% of the amount of BZT you originally used, then increase (or decrease) the amount as needed.

    I would try developing short pieces of unexposed film in order to determine the minimum amount of BZT per liter that is required to suppress fog with PC-TEA.

    Alternatively, try Hovie's suggestion of using Potassium Bromide instead of BZT as the restrainer.
     
  5. aldevo

    aldevo Member

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    Well, as luck would have it, I think I've found the problem...

    First of all, the mistake is my own, not Sandy King's.

    Sandy recommended 1 ml of 1% BZT solution per liter of working solution not per roll to be developed. So I've used approximately 3X the recommended amount.

    For whatever reason I can't find Sandy's original post on photo.net but I partial transcription is (apparently) available at:

    http://www.freelists.org/archives/pure-silver/01-2005/msg00386.html

    So it's a reading error on my part. What is it that mothers are so fond of saying? "Act in haste, regret at leisure".

    Mea Culpa, Sandy!

    I've already diluted my original 300ml of 1% BZT solution to 1000 ml so I'm probably already in the ballpark. I'll probably halve the amount just to be sure (there are worse things than a bit of base fog!) in my initial trial.