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  1. #191

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    Rudi,

    Thanks for the kind posting. I'm glad not everybody is bored with this detailed engineering-work.

    I think Borax would work fine. My reluctance in using is (1) it carries much water with it (10H2O IIRC), which would need to be steamed out of the concentrate, and (2) a greater quantity would be required to raise pH to the desired level, requiring that more concentrate be used per litre. I know it's difficult for relayer to find in Ukraine, but can't Europeans buy metaborate easily from the UK and Germany? For mixing directly into water, Borax dissolves slowly. So if metaborate is unavailable, I'd suggest trying TEA instead of Borax.

    PG reduces pH slightly and slows development a bit. It can be omitted from direct-to-water brews by reducing development-time slightly.

    Good point about T-grain films containing less silver. I'll do my capacity-tests using the brick of Tri-X I have in the freezer.

    Mark Overton

    Quote Originally Posted by Rudeofus View Post
    Mark,

    first let me express my amazement and my gratitude that you go through all this effort and document not only the final results but also all these important intermediate steps which got you there. There are two variations to this experiment which would interest me personally and which might be of interest to others:
    • Effect of using Borax instead of Metaborate. The latter one is more difficult to get and with a pH of around 8 Borax should be more than alkaline enough to work. It will take a tad more Borax than Metaborate which means we will get better buffering, which in turn means possibly reduced sharpness. Since we turn a lot of wheels here when changing from Metaborate to Borax, a practical experiment could be most helpful.
    • Effect of PG on dev performance. Quite often I see stock developer recipes (think Pyrocat HD, PC-TEA, ...) but need only one or two rolls of film processed, so I'd like to skip the solvent for the concentrate. This would be poor advice with TEA, of course, but what about PG? PG is neither a silver solvent nor an alkali, so leaving it out should have less effect, but from what I read it does interact with the Metaborate. A quick experiment could shed some light on this.


    PS: There are a few tricks which could reduce the cost of dev capacity testing: If you use fully exposed test rolls instead of step wedges, you put a lot more strain on the dev, since more silver halide gets reduced. Second, from what I read, T-grain films have less silver than traditional films, so traditional films might again need more dev than TMY2. For testing dev capacity, I'd go with the cheapest traditional 400 speed film you can find.

    PPS: Since you design a dev here for very casual home developers, I'm not sure whether we need to squeeze the last penny out of its raw materials. One might as well err a bit on the high side without much financial effect.

  2. #192

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    I got thinking more about the speed-loss graph, and realized that it might be more widely applicable if the X-axis were changed to the ratio of sulfite to Phenidone. Here's the modified graph:

    Click image for larger version. 

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    When the sulfite/Phenidone ratio is over 900, the speed-loss shoots up. When it's below 800, grain gets worse. So the range 800-900 is ideal. But is this true of other developers? XTOL was carefully designed, and I've found that .105 g of Phenidone substitutes for .2 g of DimezoneS. So XTOL's sulfite/Phenidone ratio would be 88/.105 = 838, which is in the ideal zone.

    Note that speed (EI) increases as you go left on the graph. What happens if you decrease the sulfite/Phenidone ratio to around 200? I tried that in January by semi-accident, and got a developer that yields high speed and more grain. If you develop with it to a low contrast (i.e., under develop), you get normal shadow-detail (i.e., box speed) and wide dynamic range for high contrast scenes. Rudeofus: This is the low contrast dev you used a few months ago.

    Anyway, this is something for designers of PC-type developers to be aware of.

    Mark Overton

  3. #193

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    Here's a question for chemists:

    Does alkalinity or acidity affect the propensity of a non-aqueous (PG-based) concentrate to crystallize?

    I've seen two kinds of crystallization: (1) the white kind described in earlier postings, where the concentrate separates into a white cream and the PG solvent, and (2) some clear cubical crystals growing on the bottom and low-sides of the bottle (not precipitate). DimezoneS in PG, or very high concentrations have caused (1). A fairly high concentration-ratio of 0.46 caused (2) in one bottle. BTW, I define "concentration-ratio" as WeightOfPowdersInGrams/VolumeOfConcentrateInMl. Now, the bottles that have crystallized have also been rather alkaline (giving higher pH when mixed with water), whereas the stable ones have lower pH. So I'm wondering if high pH makes a concentrate more prone to crystallization.

    TIA for any clues about this.

    Mark Overton

  4. #194
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    Mark;

    There are many crystal habits from cubes to octahedra to needles to plates and etc. Each chemical has a typical crystal habit which is partly based on the solvent from which it precipitates. The pH is not directly related to crystal formation. Crystal formation is related more to the concentration of all of the materials present.

    PE

  5. #195

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    Quote Originally Posted by Photo Engineer View Post
    Mark; There are many crystal habits from cubes to octahedra to needles to plates and etc. Each chemical has a typical crystal habit which is partly based on the solvent from which it precipitates. The pH is not directly related to crystal formation. Crystal formation is related more to the concentration of all of the materials present. PE
    Ron, thanks as always for the help! It looks like I'd better keep those concentration-ratios down.

    Also, I haven't forgotten DimezoneS. My tests show that, compared with Phenidone, it gives slightly higher speed (EI) and lower fog, with the same grain. I'd like to take your suggestion from many months ago and use TEA instead of metaborate in the DimezoneS-based formula that crystallized. The resulting formula will be similar to the organic solvent version of Instant Mytol (Jordan Wosnick). I plan on doing this work after finishing the Phenidone formula described in recent postings. Plus I want to work on a low contrast developer. Plus C-41 developers. There are too many things I want to do! This hobby is making retirement sound good.

    Mark Overton

  6. #196

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    Quote Originally Posted by albada View Post
    I think Borax would work fine. My reluctance in using is (1) it carries much water with it (10H2O IIRC),
    Anhydrous borax is available commercially. You could also make your own.
    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

  7. #197

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    Quote Originally Posted by Gerald C Koch View Post
    Anhydrous borax is available commercially. You could also make your own.
    I didn't know an anhydrous form was available. Thanks for pointing that out. And a bit of searching showed that making it myself means heating Borax to near the melting point of steel. Wow! Or would heating it in an oven actually drive out all the water? There's a long posting near the bottom of this page that's interesting: http://www.bladeforums.com/forums/sh...nhydrous-borax

    Yet more questions...

    Regarding crystallization: Does temperature affect the rate of growth of crystals? I would expect higher temp to increase the rate, but higher temp also boosts solubility, which might hinder crystal-growth. I'd like to do an accelerated test for crystallization, and was wondering if keeping the bottle hot would help or hurt.

    Regarding TEA: I know that TEA is a solvent for silver halide, but how does it compare with sodium sulfite? 1 ml of TEA has the solvent-effect of how many grams of sulfite? When I add X ml of TEA, I'm wondering how many grams of sulfite to reduce to keep the same net solvent-effect. (I know sulfite does other things too, so it's all trade-offs).

    TIA,

    Mark

  8. #198
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    Mark;

    Temperature has a profound effect on crystallization with the rate generally going up as temperature goes down.

    TEA, AFAIK, is much less of a silver halide solvent than Sulfite.

    PE

  9. #199

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    Great find on the pH meter! That should give much better results than your old one. Keep looking for a temp probe. It may be cheaper to get a second electrode with a built in temp sensor than buying the sensor outright.

  10. #200

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    Quote Originally Posted by albada View Post
    I didn't know an anhydrous form was available. Thanks for pointing that out. And a bit of searching showed that making it myself means heating Borax to near the melting point of steel. Wow! Or would heating it in an oven actually drive out all the water?
    In a pinch you can prepare small quantities of anhydrous borax with the help of a Meker burner. The borax must be fused to drive off all the water. A Meker burner produces a flame of 1500oC which is hotter than a Bunsen burner can produce. But fortunately this form of borax is cheap.
    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



 

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