About to mix PC-TEA, two questions left

Discussion in 'B&W: Film, Paper, Chemistry' started by mcilroy, Mar 22, 2011.

  1. mcilroy

    mcilroy Member

    Messages:
    55
    Joined:
    Nov 9, 2010
    Location:
    Germany
    Shooter:
    Multi Format
    I'm about to mix some PC-TEA for the first time. The shop from which I bought the chemicals had TEA and ascorbic acid with the highest purity (> 99%), but Phenidone with 97%.
    Should I use the amount given in the formula, or use a little more (such as X/0.97)? I guess it's nothing to be worried about... :whistling:

    My second concern is about how much Phenidone to use. The 3rd edition of the Darkroom Cookbok specifies 0.5g per 100ml Stock, most sources state 0.25g for the same volume. Does the larger amount just provide some safety for higher dilutions or does it significantly change the results in normal use (i.e. one-shot use, dilution 1+50 and two rolls of 135/36 per 500ml).

    Matthias
     
  2. Alan Johnson

    Alan Johnson Subscriber

    Messages:
    1,514
    Joined:
    Nov 16, 2004
    It's hard to weigh the small amount of phenidone with 97% accuracy and it probably has no detectable effect until the error is notably larger.
    I have always used the formula here:
    www.photosensitive.ca/wp/?s=gainer
    Some times are here:
    www.digitaltruth.com/devchart.php?Film=&Developer=PC-TEA&mdc=Search
    or see under "unlisted data" ; for PC-TEA use Xtol 1+2 times ( I assume this refers to the 1:50 dilution).
    I expect these times would have been found using the 0.25g Phenidone version.
    It's hard to say what would happen if the Phenidone is doubled as in the Cookbook version.
     
  3. mcilroy

    mcilroy Member

    Messages:
    55
    Joined:
    Nov 9, 2010
    Location:
    Germany
    Shooter:
    Multi Format
    Thanks, Alan! Yes, ist seems that the "0.25g forumla" ist by far the most used. Accourate weighing would not be the problem, since I got a very good scale from my uncle who worked as a chemist. But of course even the best scale will show inaccuracy to some degree, unless it's being calibrated regularly.

    I wonder what's the reason for the differing instructions in the Cookbook. They don't give a clue and it's unlikely to be a typo because i read somewhere that it was adopted to the newest edition from the last one.

    EDIT: Found two posts by gainer regarding the issue in this thread:
    and
    He was using 0.225g and 2.25g for this comparison, so it seems one can use 0.25g as well as 0.5g without hesitation. However, 0.225g (1/40th of the amount of ascorbic acid) should be the absolute minimum.
     
    Last edited by a moderator: Mar 22, 2011
  4. bwrules

    bwrules Member

    Messages:
    198
    Joined:
    Jun 18, 2008
    Shooter:
    Multi Format
    I don't have a scale, so that's how I mixed it - with 1:40 ratio. For 1:50 dilution the times correspond with the Xtol 1:2. For 1:25, it's Xtol 1:1 times. I don't like long development times.
     
  5. P C Headland

    P C Headland Subscriber

    Messages:
    744
    Joined:
    Mar 24, 2005
    Location:
    Wellington,
    Shooter:
    Multi Format
    I mix mine with 0.25g of Phenidone per 100ml.

    I tend towards an average of Xtol 1+1 and Rodinal 1+50 times for developing in PC-TEA 1+50. If those times are very different, I'll also consult the D76 1+1 times.

    If in doubt, 9-10 minutes is a good starting point for 1+50.

    BTW, the concentrate has a very good shelf life, with no discernible change in activity after more than three years, even when the colour has changed from dark straw to rather dark.
     
  6. Gerald C Koch

    Gerald C Koch Member

    Messages:
    6,246
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    Pat Gainer used a ratio of phenidone to ascorbic acid of 1:40. However many PA formulas use a higher ratio 1:60 or even 1:80. In later posts he mentioned using 0.225 g of phenidone for 10 g of ascorbic acid.
     
    Last edited by a moderator: Mar 26, 2011
  7. mcilroy

    mcilroy Member

    Messages:
    55
    Joined:
    Nov 9, 2010
    Location:
    Germany
    Shooter:
    Multi Format
    Thanks all! I went with 0.3g Phenidone to be on the safe side (can't get it 99% pure) and the first developed roll of Acros looks very promising.