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  1. #11
    BetterSense's Avatar
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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!
    f/22 and be there.

  2. #12

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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.
    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

  3. #13

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    Quote Originally Posted by Gerald C Koch View Post
    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.
    @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

  4. #14

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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
    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

  5. #15
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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

  6. #16

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    Quote Originally Posted by Photo Engineer View Post
    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
    @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

  7. #17

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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?

  8. #18
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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

  9. #19
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    Quote Originally Posted by Michael R 1974 View Post
    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?
    You mean this one?
    Trying to be the best of whatever I am, even if what I am is no good.

  10. #20
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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

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