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  1. #111

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    Mark - you've probably answered this before, but how are you exposing the test strips?

  2. #112

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    Quote Originally Posted by Michael R 1974 View Post
    Mark - you've probably answered this before, but how are you exposing the test strips?
    I place a 4x5 Stouffer transmission wedge on a uniformly lit portion of my light-table. After waiting at least 5 minutes for the florescent bulbs to completely warm up, I shoot it with an OM-1 set to 1/60 using a 50mm macro lens at f/3.5 (wide open). I chose 1/60 because (1) my shutterspeed tester says the OM-1 is very consistent at that speed, and (2) it covers exactly one complete cycle of any 60 Hz flicker in the bulbs, so that any such flicker will not affect exposure. To insure consistency, I shoot an entire roll at once, and cut out the strips as needed.

    This system works fine, but I think using a reflection step tablet outdoors in sunshine would be better because you could stop down the lens and get maximum sharpness. With my setup, I need to perform sharpness-tests separately.

    Mark Overton

  3. #113

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    Discouraging results:
    I can't get a concentrate containing Dimezone-S to stay in solution. Either immediately or in a few days, cloudiness begins appearing, and the concentrate eventually separates. Concentrates using Phenidone have not had this problem. In fact, after mixing a Dimezone-based concentrate which immediately clouded, I mixed the same formula using Phenidone with no problems (so far). I believe this clouding is the crystallization that PE described a couple of weeks ago here and here. There is something about Dimezone-S that encourages crystallization of a PG-based concentrate. Even substituting some metaborate with TEA didn't help.

    Dimezone-S is preferable to Phenidone because my tests show that, at normal pH-levels, it has lower fog and slightly finer grain. To get Phenidone to match Dimezone-S's grain and fog-level, pH must be dropped to 8.0 or lower. The developer D-316 that Alan Johnson is testing uses this low-pH approach.

    Also, I doubt my cream-and-squeeze-tube idea will work because the separation is ongoing, gauging by watching the bottle over a couple of weeks. So we'd need to stir the cream and PG before using, like natural peanut-butter. That means we cannot allow this crystallization to occur. Any ideas how?

    If all else fails, it's back to Phenidone and a pH of 7.9 or 8.0.

    Mark Overton

  4. #114

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    Dimezone was developed to avoid the problem of hydrolysis that occurs with Phenidone in alkaline solution. Unfortunately Dimezone turned out to be less soluble in water than Phenidone. To correct this the structure of Dimezone was altered slightly to make Dimezone-S (S for more soluble). Google the three structures to see what was done. At the pH of the developer you are working on there would be no problem with hydrolysis. So there is no reason that you cannot use Phenidone. I have never heard anyone other than yourself say that Phenidone produces more fog than Dimezone-S. A small amount of fog is always produced during development and really cannot be avoided. If you attempt to eliminate all fog produced by a developer with bromode or benzotriazole the activity of the developer is serverely compromised.

    As far as activity there does seem to be less activity with the two Dimezones as compared to Phenidone that cannot be explained by the slight increase in molecular weights. So replacing one developing agent for the other is problematic in this respect. Perhaps this accounts for the increase in fog that you observed when Phenidone was used. You were simply using more Phenidone in relation to Dimezone-S.

    Yeats ago there was a developer called Huebl paste which was produced by grinding Glycin, sodum sulfiie, and potassium carbonate together in a mortar. A portion of this paste was then dissolved in water to make a developing solution. (Huebl is an alternative spelling of the man's name when there is no umlaut U in the type set)
    Last edited by Gerald C Koch; 08-05-2012 at 02:25 AM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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  5. #115

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    Some Mytol (contains phenidone) I kept in a sealed glass bottle lasted over 3 years,by 5 years it failed due to phenidone hydrolysis I believe.Unless you are planning to present your concentrate to a Museum I daresay phenidone would be adequate for the purpose, particularly as the unmixed concentrate has a lower pH than the working solution.

  6. #116

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    @Jerry: The symptoms of crystallization are the developer turning white like milk, and then separating over days. This happened to me once when there was no developer present. But the concentration was extremely high because I was trying to find a solubility-limit for PG. So I learned that PG + sodium metaborate + ascorbic acid can crystallize. The Dimezone S seems to encourage and/or cause it though. So I think something other than hydrolysis is happening.
    Also, Phenidone's higher fog is based only on my observations. But when I drop pH, fog-levels are comparable. One interesting thing I've noticed: Phenidone is almost exactly twice as active as Dimezone S in these formulations I've been testing. Odd, isn't it? Formulas I've seen more commonly use a factor of something like 1.33. But my densitometer tells me it's 2.0. Go figure...

    @Alan: Regarding the 3-5 year lifetime of Mytol: Was your Mytol the original created by Paul Lewis, or the organic concentrate created by Jordan Wosnick which he calls "Instant Mytol"? I have a bottle of the concentrate mixed 9 months ago, and it shows no sign of crystallization.

    Anyway, this crystallization-issue with Dimezone-S got me thinking about a developer I devised 6 months ago using Phenidone. So I re-mixed and ran another test-strip with it. Here's the one-litre formula for mixing directly into water:

    45 g Sodium sulfite
    2 g Sodium metaborate
    4.5 g Ascorbic acid
    2.45 g Propylene glycol (yes, grams)
    0.05 g Phenidone (which was premixed into the above PG as a 2% solution)

    pH = 8.05 to 8.1. For TMY2: 13.25 minutes at 20C.

    And the density-curves comparing it with XTOL:

    Click image for larger version. 

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    I've never seen such close graphs. The grain looks the same as XTOL under close exam on the light-table with 22X loupes.
    Keeping sulfite separate, this formula should be able to be dissolved into PG, with a total volume of 20 ml, yielding a concentration ratio of 6.55/20 = 0.33, and a dilution of 1+49.
    Alan: This is the same as D-316, but with the metaborate changed from 2.2 g to 2.0 g. So it's almost the same developer.
    But it's rather different from XTOL. The dev-times are different, and more importantly, films respond to pH differently, so dev-times won't change by a simple factor. So this would require more testing than an XTOL-clone.

    I think I'll try an XTOL-clone with Dimezone-S again, but using TEA instead of sodium metaborate. If the crystallization is from by-products of the reaction of metaborate with ascorbic acid, then TEA might fix the problem.

    Mark Overton

  7. #117
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    Quote Originally Posted by albada View Post
    So I learned that PG + sodium metaborate + ascorbic acid can crystallize. The Dimezone S seems to encourage and/or cause it though. So I think something other than hydrolysis is happening.
    This is just a simple theory based on lack of knowledge, but could it be that the precipitate is oxidized ascorbate?

    Here is what hints in that direction:
    1. Oxidized products of ascorbate have no distinct color, i.e. you don't see when it happens in water.
    2. We know that Phenidone/Dimezone S catalyzes oxidation of ascorbate, that's why it is superadditive
    3. We know that this happens more likely in caustic environment, hence you see it faster with metaborate

    A very quick'n'dirty test would be, of course, if you would try developing a test clip of film with the soup once it precipitates.

    Quote Originally Posted by albada View Post
    And the density-curves comparing it with XTOL:
    I've never seen such close graphs. The grain looks the same as XTOL under close exam on the light-table with 22X loupes.
    I would like to know to which extent variations in composition have a visible effect on characteristic courve, grain, sharpness, etc. Since you have obviously done lots of experiments before you came up with your final result, could you comment on that? Would a 10% variation make a big difference or does it take much more before you saw anything different?
    Trying to be the best of whatever I am, even if what I am is no good.

  8. #118

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    Mark,

    My Mytol was the water based solution from p89 of the Film Developing Cookbook.The 3 year life in absence of air has not been verified by others AFAIK.For Dimezone-S, 7.5 year some life was reported with anaerobic Xtol:
    http://www.apug.org/forums/forum37/1...ties-xtol.html
    Your precipitate may be glycol-borate complex ,we will never know.I don't think esters are formed at the mixing temperatures you use:
    http://www.chemicalforums.com/index.php?topic=41216.0

    For other PC developer PC-TEA when selecting development times for different films I have used a simple multiplier of Xtol time,is there any reason not to use this with one of the concentrates?

  9. #119

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    Quote Originally Posted by Rudeofus View Post
    We know that Phenidone/Dimezone S catalyzes oxidation of ascorbate,
    This is just not true you misunderstand the meaning of catalysis. Ascorbate ion reduces oxidized Phenidone/Dimezone back to the parent compound. However this is a moleculae for molecule process not the massive oxidation of the ascorbate that your statement implies.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  10. #120
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    Quote Originally Posted by Gerald C Koch View Post
    This is just not true you misunderstand the meaning of catalysis. Ascorbate ion reduces oxidized Phenidone/Dimezone back to the parent compound. However this is a moleculae for molecule process not the massive oxidation of the ascorbate that your statement implies.
    But in the end it has the effect of a catalyst. Ascorbate, which would reduce silver very slowly on its own if at all (especially at pH of 8), does it rapidly in the presence of trace amounts of Phenidone or Dimezone S. During regular film development, a lot more Ascorbate is oxidized than Phenidone. Curious why this wouldn't count as a catalytic reaction.
    Trying to be the best of whatever I am, even if what I am is no good.



 

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