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  1. #191
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    Well, try using Potassium Sulfite.

    If you want higher contrast try about 0.2 g/l of Phenidone.

    I would also use it at 50 ml of concentrate to 19x water (950 ml) to make 1 L for a 1:19 mix. That is generally the convention. You are using 50 ml in 1L which is 1:20 but making a bit more. But that is fair, if that was your goal. It is just a bit more dilute.

    Very nice. Remember though that lower contrast appears to lower grain and sharpness, so you may have more sharpness than you think!

    PE

  2. #192

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    Quote Originally Posted by albada View Post
    I poured all the chemicals into the PG at the same time, instead of waiting for them to dissolve separately. [...]
    Thatís a lot of work. Why donít you leave it at a powder mix??

    Target pH is somewhere around 7.4 (I need a pH-meter!). Add 15% to XTOL's times, because this developer is similar to XTOL as it uses the same chemicals in similar proportions.
    You apparently didnít study my old posts. There is a very good reason why pH of DS-10 is 8.0, and XTOL is 8.2.

    XTOLís pH of 8.2 is probably the lowest pH where the developer can work reasonably well with all then-current films.

    DS-10 chose 8.0 because I wanted slightly finer grain just for developing 400-speed films or faster (I almost always use a more accutance formula for 100-speed tabular grain films). DS-10 does not work (just donít get enough density and contrast regardless of development time) with some films, all 100-speed or slower.

    If you are doing pH of 7.4 that must be really well tested and come with a caveat. I think it is too risky to propose as a practical solution. But then how do you know pH without a good pH meter??

    Also, how did you compare granularity and image quality if you developed the film to a different contrast index? It is an utterly unfair comparison. If you want lower contrast results, then you should compare yours against DS-10 further diluted or processed shorter or otherwise finished to the same CI. Any developer can produce better granularity if you terminate development prematurely.

    It has no chelating agents, so I suspect it can only be reliably used with distilled/deionized water, and I still wouldn't trust a working solution that's over a few hours old.
    Youíd better read my old posts. The main source of iron is the impurities in the sulfite stock. But then stainless steel used in tanks and reels does release some iron into water, although small, it can be readily detected.

    A question:
    Why is the contrast lower?
    Because you lowered pH and thus lowered the developerís reduction potential.

    Iíll speculate that this developer has poor (nonexistent?) buffering because I removed the boric acid, and that causes the pH to drop more in dense areas, hindering development more in dense areas. That is, the poor buffering is causing compensation. Or am I off in the weeds about this?
    Borate has nearly no buffering effect at pH of 7.4. Itís not the ingredients you used but what are actually present in the solution at the particular mixture, pH, temperature, etc.

  3. #193

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    Quote Originally Posted by Photo Engineer View Post
    Well, try using Potassium Sulfite.
    If you want higher contrast try about 0.2 g/l of Phenidone.
    Does Potassium Sulfite boost contrast? Is it a halide solvent too? I did a brief search for this on apug.org, but didn't see anything definitive.

    Quote Originally Posted by Photo Engineer View Post
    I would also use it at 50 ml of concentrate to 19x water (950 ml) to make 1 L for a 1:19 mix. That is generally the convention. You are using 50 ml in 1L which is 1:20 but making a bit more. But that is fair, if that was your goal.
    Actually, my goal is what you described: 1 part concentrate plus 19 parts water, making 20 parts (50ml + 950ml). I guess I should have been clearer.

    But what do you suppose is reducing contrast? Compensation due to poor buffering?

    Mark Overton

  4. #194

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    Quote Originally Posted by Ryuji View Post
    Thatís a lot of work. Why donít you leave it at a powder mix??
    Because the concentrate is more convenient for me. Although with only four chemicals, this developer would be easy to mix-when-using. BTW, I have no intention of making this a product for sale. It's for my own use, and helps me to learn about formulating developers.

    Quote Originally Posted by Ryuji View Post
    You apparently didnít study my old posts. There is a very good reason why pH of DS-10 is 8.0, and XTOL is 8.2.
    XTOLís pH of 8.2 is probably the lowest pH where the developer can work reasonably well with all then-current films.
    I probably read this and forgot it. Forgetting is one of my "core competencies".

    This is interesting: I had no idea that some films won't develop properly below 8.0 or 8.2. I'm only creating this developer for myself, so I'll only test it with films I use, which are all 400-speed (TMY, TX). I suspect that this will be a niche developer. I'm measuring pH using two brands of test strips, so my measurements are probably +/- 0.2. That 7.4 might be 7.6.

    Quote Originally Posted by Ryuji View Post
    Also, how did you compare granularity and image quality if you developed the film to a different contrast index?
    I'm judging granularity, contrast and sharpness using a pair of identical 22X loupes placed on the negatives. I quickly hop back and forth between them on the light-table. So all these judgments are qualitative and not quantitative. I'm aware that proper engineering requires quantitative measurements, but for preliminary personal work like this, qualitative is good enough for now. I'm a newbie still learning about all this, so I don't have the more costly lab equipment yet.

    Quote Originally Posted by Ryuji View Post
    The main source of iron is the impurities in the sulfite stock.
    I remembered that one, and that's why I said I wouldn't trust working solution that's over a few hours old. So I'm not forgetting everything.

    Quote Originally Posted by Ryuji View Post
    Because you lowered pH and thus lowered the developerís reduction potential.
    And that makes me ask another newbie question (if you don't mind): I would expect reduced potential to reduce everything the same amount, making the negative uniformly thinner. But reduced contrast means highlights were reduced more than shadows. My question: How does reducing potential reduce contrast?

    Anyways, thanks for your patience with my questions. I learn, and I try a developer like this one, and get surprising results, and learn more.

    Mark Overton

  5. #195
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    Quote Originally Posted by albada View Post
    Does Potassium Sulfite boost contrast? Is it a halide solvent too? I did a brief search for this on apug.org, but didn't see anything definitive.



    Actually, my goal is what you described: 1 part concentrate plus 19 parts water, making 20 parts (50ml + 950ml). I guess I should have been clearer.

    But what do you suppose is reducing contrast? Compensation due to poor buffering?

    Mark Overton
    Mark;

    Potassium Sulfite is the same in activity as Sodium Sulfite but at a slightly higher concentration to compensate for molecular weight. It is however, far far more soluble. It can be purchased from the Photographers Formulary as a stock solution. That is where I get mine.

    The low contrast may be due to pH, low Phenidone concentration (noted in my last post) or under development. The pH strips used by many can be off by quite a bit. They are good for an approximation but not for this type of critical work. Get a Hana meter for about $80. They use a Silver/Silver Chloride and Silver billet electrode set that is compatible with this type of work.

    Best wishes in your work. You are doing quite well.

    PE

  6. #196

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    Quote Originally Posted by albada View Post
    This is interesting: I had no idea that some films won't develop properly below 8.0 or 8.2.
    That is for developers that share the same basic design as XTOL or DS-10. It is not a universal law for all developers.

    I'm measuring pH using two brands of test strips, so my measurements are probably +/- 0.2. That 7.4 might be 7.6.
    pH test strips are inherently inaccurate and an error of 0.2 unit is significant for a film developer.

    I'm judging granularity, contrast and sharpness using a pair of identical 22X loupes placed on the negatives. I quickly hop back and forth between them on the light-table. So all these judgments are qualitative and not quantitative. I'm aware that proper engineering requires quantitative measurements, but for preliminary personal work like this, qualitative is good enough for now. I'm a newbie still learning about all this, so I don't have the more costly lab equipment yet.
    Then be careful when you report your findings. Using words like "better" based on subjective comparison without equalizing the conditions is only going to undermine credibility of the statement.

    And that makes me ask another newbie question (if you don't mind): I would expect reduced potential to reduce everything the same amount, making the negative uniformly thinner. But reduced contrast means highlights were reduced more than shadows. My question: How does reducing potential reduce contrast?
    I think you need to do serious study of electrochemistry and modern theory of development process. It's not easy to describe this to people without proper background... First of all, you should make absolutely sure whether the speed (as measured 0.1d above base plus fog) did not change, as I bet it lowered. But then the development is not one process that uniformly progresses. It is a multi-step process. Developer parameters often affect each stage differently. Let's leave it at that for now, trying to add on a gross simplification is going to be wrong.

  7. #197

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    I goofed!

    I re-measured, and the pH of that last developer is around 7.8-7.9, and I edited that posting to reflect this correction.
    That's what I get for relying on my memory for an hour instead of writing things down immediately.

    Anyway, PE suggested a Hanna meter, and I'll see if Grainger industrial supply (which is near me) has it in stock. If not, it'll be an internet order.

    Mark Overton

  8. #198

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    Mine is Hanna HI-9125 but I replaced the electrode with a separate one that is refillable double junction type. Most kit comes with single junction or gel-filled electrodes. They are no good for photographic work. You want to make sure your electrode is "refillable" AND "double junction." You want to drain and refill the KCl solution in the electrode at the end of each shift, and calibrate the system at the beginning of each shift.

  9. #199
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    This unit is just fine: http://www.hannainst.com/usa/prods2....ode=HI%2098127

    I have 2 of them and have used them for years.

    Here is more information: http://www.hannainst.com/manuals/manHI_98127_98128.pdf

    There should be no problem with measuring developer or fixer pH.

    For extra critical work I use a VOM with my own plated silver electrode and a triple junction electrode.

    PE

  10. #200

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    Chemistry time!
    Based on my rusty knowledge of chemistry, I think this is what will happen when ascorbic acid and sodium metaborate are mixed together:

    2C6H8O6 + 2NaBO2 => 2C6H7NaO6 + H2O + 2B + 3O
    They form sodium ascorbate, which we want. But will they also form that H2O above?
    Will this reaction occur in the propylene glycol solvent? If so, it'll be adding 0.55 ml of water (per 50 ml concentrate), which is about 1%. That may not hurt, but I'd prefer the water-content be 0%. Also, what will those extra 2B and 3O form?

    Quote Originally Posted by Photo Engineer View Post
    This unit is just fine: http://www.hannainst.com/usa/prods2....ode=HI%2098127
    I have 2 of them and have used them for years.
    I ordered one from Grainger, and will pick it up tomorrow. The in-person pick-up will allow me to verify on the spot that the electrode is wet.

    Mark Overton



 

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