Diluting Perceptol Developer

Discussion in 'B&W: Film, Paper, Chemistry' started by johnnywalker, Dec 27, 2003.

  1. johnnywalker

    johnnywalker Subscriber

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    I received Barry Thornton's book "Edge of Darkness" for Christmas. One of the things he recommends is to reduce the rated film speed by half and develope it in diluted Perceptol. I intend to try this with HP5+ rated at EI 200.

    I have a question out the dilution. In my Paterson tanks, each film needs 300 ml of developer. According to Ilford, one litre of stock Perceptol will develop 5 rolls of film. So in my 5 reel Paterson, I need 1500 ml of developer, or a dilution of 1+0.5. I figured out a time for this of 10.5 minutes @ 20 deg. C. Thornton however is talking about a dilution of 1+2, or 3000 ml, or 600 ml per roll.

    If I want to go with the 1+2 dilution should I just develope, say one roll with 600 ml of developer, or two with 1200 ml of developer? I know the times are different, but is this the "equivilant" (the benefits of dilution aside) of using 300 ml of 1+0.5? The total amount of chemicals per roll of film is the same in either case.

    TIA, and hope everyone had a Merry Christmas,

    John

    p.s. I'm also getting "Creative Black and White Photography" by Les Mclean. Unfortunately it's on back-order, but they should make a great pair.

    J.
     
  2. Leon

    Leon Member

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    Hi Johnny

    I have found HP5 works better at ei 160 in dilute perceptol, although thats probably more to do with my technique peculiarities. I usually dilute to 1:3 to make 600 ml (150ml stock and 450ml water), then use this at 24 degrees with 2 x 120 rolls placed on one plastic reel - my tank will only take 1 reel when extended to the 120 width. Although, on the odd occasion when I develop 1 roll, i still use 600ml to be sure.

    I find 1:3 gives a more compensatory effect than 1:2 and the edge effects seems to have the edge on the stronger solution (if you see what I mean!), although develpment times are fairly long.

    Have you read Barry Thornton's Elements too? I find this much more useful than the already very good Edge of Darkness.

    Hope this helps.
     
  3. john_s

    john_s Subscriber

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    When using highly diluted developers, the usual advice is to use a generous amount to ensure that you get the effect of dilution and not exhaustion.

    However, many people report that you can get away with using less than is often recommended. If the developer becomes exhausted, one result would be less contrast which might be one of the things that you're looking for.

    Am I correct in surmising that another effect of ddilute developer exhaustion (of the whole lot, not just local exhaustion which is the aim of this technique) would be poorer shadow density, not able to be compensated for by longer development?

    My reason for asking is that I'm experimenting with Pyrocat-HD at half strength for minimal agitation use. I'm very encouraged by initial prints. But I did use 1Litre per 80sq.in (5+5+1000) which is probably excessive. It's certainly a bit inconvenient.

    Sandy has stated that 200mL of standard (2+2+200) is the recommended minimum quantity. Half strength of that quantity of developer would be 400mL. Would that be enough to prevent developer exhaustion? (Leaving aside issues of actually covering the film)
     
  4. Leon

    Leon Member

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    As i understand, there are two main reasons for using dilute perceptol (specifically).

    1. to slightly reduce the effect of the grain disolving ingredient, thereby increasing accutance (although, this doesnt seem to leave a noticably higher grain in the negative, just better edges); and,
    2. to effect a controlled exhuastion of the developer while it is working which serves to compensate for high subject brightness ranges, although clearly not to the extent of two bath or water bath development. For it to work effectively, agitation and stand times must be well ballanced - i use slow but constant agitation for 30 secs, then one inversion of the tank every 30 seconds and find this is sufficient for two 120 rolls in 600ml of 1:3 perceptol, then as it stands, the shadow (thinnest) areas of the neg continue to develop as the highlight (densest) areas quickly run out of steam.

    I have not noticed any substantial overall thinning of the negative using this method and find it gives me fine negatives for scanning and/ or printing.