Progress on XTOL-concentrate

Discussion in 'B&W: Film, Paper, Chemistry' started by albada, Jul 8, 2012.

  1. albada

    albada Member

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    Although I've been quiet for weeks, I've still been busy trying to create a concentrated version of XTOL that will keep for years. I think I'm close. Below is the graph of true XTOL versus my test-dev (TMY2, 6.5 min at 20C):
    t.jpg
    As you can see, the two curves are so close that they appear to be one curve in the thumbnail. And careful exam in my 22X loupes shows the grain is the same too. Here's the formula:

    Propylene glycol .................... 24 ml
    Sodium metaborate 4 mol ..... 6.7 g
    Ascorbic acid ......................... 8.5 g
    DimezoneS/Phenidone .......... 0.2 / 0.105 g
    Propylene glycol to ................ 33.3 ml (final volume)
    (heat to 90C to dissolve everything and drive out the water in the metaborate)
    To make one litre of developer, mix 33.3 ml of concentrate into water containing 90 grams of sodium sulfite. That's 1+29 dilution.

    So far, I've tested this by mixing the ingredients directly into water; I haven't actually made any concentrate yet. That's the next step.

    Chemists will be interested in the latest weird problem I had:
    Adding the propylene glycol to that developer drops the pH by .07 and raises the temperature by 1 degree C. So it appears to react with something. Adding PG to XTOL does not change its pH, and the only thing my dev has that XTOL lacks is ascorbic acid, so I'm guessing that AA reacts with PG. The dev works fine anyway, but I had to remove a little acid and add a little alkali to correct the pH. PG is not as inert as I thought. Do the chemists here have any idea what's happening?

    Mark Overton
     
  2. michael_r

    michael_r Subscriber

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    Hi Mark, I can't remember - why didn't you use sodium isoascorbate in your formula? Sorry if this was addressed in the previous thread but I didn't have the time to re-read everything. Nice to see you've continued with this project.

    Michael
     
  3. yeknom02

    yeknom02 Member

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    Speaking of the older thread, can someone link to it? I'd be interested to read what's been going on until now.
     
  4. albada

    albada Member

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    Responding to both questions:

    @Michael R 1974: I used ascorbic acid instead of isoascorbate because ascorbic acid is easy to obtain. You can even buy it at health food stores, whereas isoascorbate was not even sold by Photo Formulary the last time I checked.

    @yeknom02: Here's the link to the long DS-10 thread:
    http://www.apug.org/forums/archive/index.php/t-98430.html
    This is basically all my questions, answers and discussion about developers and my unexpected experiences with them as I was learning about the topic. Home-brewing developers is full of surprises. Several knowledgeable people contributed much good information in that thread, so it's worth reading.

    Mark Overton
     
  5. albada

    albada Member

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    By the way, here's a trick I've been using to develop short test-strips uniformly with a small amount of developer. I hold a strip to the bottom of a stainless steel tank using hobby-magnets. Here's a photo of a strip after fixing:
    HoldNegsMagnets.jpg
    Be sure the emulsion is facing up! The magnets don't rust, so they should not cause iron-contamination. But they stick poorly to the tank, so there are four more magnets under the bottom of the tank to hold those inside-magnets in place (8 magnets total). I develop in a water-bath to hold temperature to within .1 or perhaps .2 degree C, agitating with inversions. I use 100 ml of developer, but 50 ml would probably work also. I'm getting good consistency with this set-up, so I figured I'd share it with other experimenters.

    Mark Overton
     
    Last edited by a moderator: Jul 9, 2012
  6. Rudeofus

    Rudeofus Subscriber

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    Propylene glycol is a weak acid which may lower your pH to some extent. A rise temperature may or may not indicate a chemical reaction in the most narrow sense, think about dissolving sodium thiosulfate in water.
    XTOL may be much more buffered than your dilute soup. Which brings up an interesting point: Can you see a difference in edge definition between XTOL and your soup?

    @Michael: I have no idea why people would recommend sodium ascorbate instead of ascorbic acid, when the latter one is so easy to obtain from any third rate pharmacy.
     
  7. Alan Johnson

    Alan Johnson Subscriber

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  8. albada

    albada Member

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    @Rudeofus: The buffering should be similar to or even better than XTOL, because the AA will improve buffering some and I'm using more metaborate. However, I wrongly thought that PG was neutral. I gotta check these things in the CRC Handbook.

    @Alan: The pH (with the PG mixed in) is 8.33, which is .04 higher than the 8.29 I measured for XTOL. The dev-times are intended to be the same as XTOL. I used 6.5 min @ 20C for TMY2. That article about differing dissociation-constants is interesting. Thanks for pointing that out.

    Mark Overton
     
  9. Rudeofus

    Rudeofus Subscriber

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    I'm not sure how you arrive at this conclusion. Xtol uses about 100g powder per 1l of regular soup, while your soup uses about 15 g/l, so even diluted Xtol has more powder per liter. I don't know the composition of Xtol but would assume that some of that amount of powder helps buffering. AA has pKa values of 4.1 and 11.8, which will not help buffering around pH of 8.3.
     
  10. Photo Engineer

    Photo Engineer Subscriber

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    Adding plain alcohol to water will raise the temperature. So, PG and water does not surprise me.

    Good work Mark. I am waiting to see the sharpness and grain. We can see the grain from an enlarged scan of your step wedge.

    PE
     
  11. BetterSense

    BetterSense Member

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    This is very interesting. I like Xtol a lot for the shadow speed and grain that it gives, but I've been worried that it's a proprietary formula and I won't always be able to get it.

    This has the added benefit of being liquid, which is more convenient to me. If I can get an HC110-like developer that is just like Xtol--wow!
     
  12. Gerald C Koch

    Gerald C Koch Member

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    Proprietary formula? The origin of Xtol is described in detail in "The Genesis of Xtol," by Dick Dickerson and Silvia Zawadski (Photo Techniques Magazine, Vol. 20, No. 5, 1999, p. 62 ff). The article also includes the formula.
     
  13. albada

    albada Member

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    @Rudeofus: My formula requires that 90 g/L of sodium sulfite be mixed in separately from the concentrate. That makes it a little more hassle than HC-110, but it also means it gains the buffering and other benefits from the sulfite.

    @BetterSense: My motive for creating this concentrate is to have something that will last for a few years. After mixing, XTOL lasts 6 months according to Kodak, and I can't use 5 litres in that time. So this concentrate is intended for people who shoot 2 rolls per month or less as a hobby. Those who shoot 3 rolls per month or more will be able to use all 5 litres of XTOL (undiluted) in 6 months. But for low volume shooters, the extra few minutes it takes to measure two things (sulfite and concentrate) is not a problem.

    @PE: Thanks for the encouragement, and the note about alcohol. From prior tests with similar formulas, I believe sharpness will equal XTOL. But I'll certainly run sharpness tests with the actual concentrate. For now, grain is the main thing I'm watching, while keeping development-times identical to XTOL.

    @Gerald: Do you know if the formula from that article matches the patent? I have the patent, but haven't been able to locate that article. If you have access to that article, can you post the formula?

    Mark Overton
     
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  15. Gerald C Koch

    Gerald C Koch Member

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    Mark,

    I have the magazines but unfortunately they are not readily available. At one time the article was on the magazine's website but when they started stressing digital they removed it. I stumbled on the article on the web a couple of years ago. Nothing ever gets removed from the web. Have you checked the APUG archives? IIRC, if not identical they were very similar except for the patent formula being divided for packaging.

    Jerry
     
  16. Photo Engineer

    Photo Engineer Subscriber

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    Bill Troop and Steve Anchell have published the XTOL formula as stated in the patent, and the patent (according to Bill) matches the patent.

    I discussed this with Bill just a few hours back.

    PE
     
  17. albada

    albada Member

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    @Gerald: I did some searching a few months ago, and came up dry. Maybe I'll try again with archive.org or whatever it's called and see if they have it.

    @PE: I weighed the two packets from my latest XTOL-purchase, and did some reverse-engineering to reconcile those measurements and the MSDS-ranges and the patent. My conclusion is that the sulfite was reduced slightly and redistributed, resulting in this:

    Dry packet A:
    Sodium sulfite ...................... 44.7 g (MSDS=44.9..)
    DTPA ................................ 1 g (from patent)
    Sodium metaborate (8 mol) ..... 4 g (from patent) (MSDS=2.6..5.2)
    Dimezone S ..................... 0.2 g (from patent)
    Total = 49.9

    Dry packet B:
    Sodium sulfite ................. 37.9 g (MSDS=37.4..40.05)
    Sodium metabisulfite .......... 3.5 g (from patent) (MSDS=2.67..5.34g)
    Sodium isoascorbate ........... 12 g (from patent) (MSDS=8.01..13.33g)
    Total = 53.4

    I'd also like to re-check this formula by mixing it and comparing pH's with XTOL, and comparing density-curves. But that will mean buying some DTPA, which I don't yet have. I'm suspicious because the pH in the patent is 8.20, but the latest and prior XTOL-batches I've purchased measured 8.29 and 8.26 with a calibrated meter. That makes me suspect the metabisulfite was reduced and/or metaborate was boosted.

    Mark Overton
     
  18. michael_r

    michael_r Subscriber

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    This is interesting. I was always under the impression the patent, while close, may not be the exact formula. So for example I assumed the listed formula for XTOL in Anchell/Troop was probably pretty close but not necessarily "it". I don't know much about patent filing, but if the patent is the formula, how is it there are still any proprietary developer formulas out there? What about the mysteries of HC-110? That formula is in Anchell/Troop too, and yet the conventional wisdom is the exact formula has never been disclosed. Another good example is Microdol-X. We know there was some kind of anti-silvering agent in there, but it is a trade secret. Why then, can't we just look up the patent?

    I'm confused. Sorry this is off topic, but if we can look up patent filings, why hasn't someone made Ilford Cooltone yet?
     
  19. Photo Engineer

    Photo Engineer Subscriber

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    USP 5756271 gives a close approximation to XTOL, the main differences being in the tweaks for manufacturing. Bill assures me, that after talking to the inventors, it is the exact formula.

    Comparison of this formula with what is posted above should give us a good comparison between the two and see what is changed or not changed.

    You can find the formula in the patent or in Anchell and Troop, p 49.

    PE
     
  20. Rudeofus

    Rudeofus Subscriber

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    You mean this one?
     
  21. Photo Engineer

    Photo Engineer Subscriber

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    Proprietary ingredients in the Microdol family are not listed in patents. There are patents to bar use and proprietary components that are kept secret.

    PE
     
  22. michael_r

    michael_r Subscriber

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    That makes more sense.
     
  23. albada

    albada Member

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    The concentrate works! Here are the two curves of XTOL versus concentrate:
    t.jpg
    As you can see, they're about the same as mixing ingredients separately, and the dev closely follows XTOL. Grain is the same. So dissolving everything into propylene glycol didn't hurt anything, despite a little scare I had when the liquid turned orange and clear again because I dissolved things in a different order. I suggest following the order below:

    Propylene glycol .................... 25 ml
    Sodium metaborate 4 mol ..... 6.7 g (dissolves in about 3 minutes)
    Ascorbic acid ......................... 8.5 g (dissolves in 7-10 minutes)
    DimezoneS/Phenidone .......... 0.2 / 0.105 g (dissolves instantly if ground in mortar-and-pestle)
    Propylene glycol to ................ 33.3 ml (final volume)

    Heat to 90C to dissolve everything and drive the water out of the metaborate.
    To make one litre of developer, mix 33.3 ml of concentrate into water containing 90 grams of sodium sulfite. That's 1+29 dilution.
    Times are same as XTOL. Target pH is 8.33.

    The only change to the formula above was to start with 25 ml of PG instead of 24 because the powders expand the liquid less than I expected, so you can start with a bit more.

    Whew! This has been a long project, and I still need to run tests on sharpness and different kinds of film. But this is looking good.

    @Alan Johnson: This concentrate is similar to D316, except for adding more metaborate to boost pH. So the keeping-test you're doing will be helpful for this as well.

    Mark Overton
     
  24. PeterB

    PeterB Subscriber

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    You might not be as far out as you think, the patent for XTOL lists the final pH as 8.20+/-0.05 which takes into account all the variations in the ingredients and the mixing process they considered at the time. You have done very well to get so close and it may not make any practical difference to the grain, sharpness or the characteristic curve.
     
  25. Alan Johnson

    Alan Johnson Subscriber

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    As far as I know there is no standard test for developer keeping properties.It seems to depend on the volume of air in the bottle compared to the volume of developer and how often the bottle is opened.
    My test has about 20% developer concentrate 80% air and the bottle is opened to air about once a month.
     
  26. Photo Engineer

    Photo Engineer Subscriber

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    There is an open tray keeping test for developers that we used at EK. I have reported this elsewhere on APUG.

    Place 1 L of developer in a standard 8x10 tray. Develop a step wedge in it. Cover with a plastic lid. Keep for 24, 48, etc hours and retest. The change in the curve will show keeping and capacity if done with the proper procedures.

    PE