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  1. #31
    Trask's Avatar
    Join Date
    Oct 2005
    35mm RF
    Very interesting, Alan. What if we cheated on the rules a bit, and allowed that we had some sodium sulfite available. Could one just add a small amount, maybe 20g/liter, without otherwise affecting the performance of the developer?

  2. #32

    Join Date
    Nov 2004
    The chemistry of Metol (free base= 4 methylaminophenol) is discussed in many books, the chemistry of p-aminophenol is not. This is because Metol replaced p-aminophenol early on.
    If you replace Metol by p-aminophenol based on the assumption that the chemistry may be similar it's really a research project.
    Metol/Ascorbate/Sulfite is known to work.

  3. #33

    Join Date
    Nov 2004
    This developer LS-1c , made from ingredients bought at local shops, is now 6 months old. It has been kept in a half full glass bottle for most of its life and has developed 9 films plus some test pieces.
    It still works after 6 months, I developed a test film in it.The pH was originally 10.4, after 3 months it fell to 9.9 and now after 6 months it is 9.7.
    A separate batch kept in a full sealed glass bottle had a pH of 10.2 after 5 months.
    This strongly suggests that the fall in pH is due to the oxidation of ascorbate by the airspace in the bottle. A relatively large ascorbate concentration to start off with means there is enough which is still not oxidized to keep the developer working and a relatively large concentration of sodium carbonate has kept the pH high enough for the developer to still work.

    LS-1c uses ascorbate to regenerate p-aminophenol.A correspondent pointed out to me that a certain Charles Thatcher took out a patent involving the use of hydroquinone to regenerate p-aminophenol nearly 100 years ago:
    This combination has more or less fallen into disuse but still a formula exists as Kodak DK-93 general purpose developer.

    LS-1c is really only of interest if proprietary chemicals are not available, IMO, as it provides a low film speed, EI<50 (Xtol EI=100).At 1+3 dilution it works as a paper developer but the results are a bit flat compared with a proprietary developer. In complete absence of photochemicals the film can be slowly fixed in table salt solution:

    As noted before, care should be taken with the caustic sodium hydroxide:

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