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  1. #31
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    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

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    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

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    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:
    https://www.google.com/patents/US115...ed=0CDcQ6AEwAA
    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:
    http://www.apug.org/forums/forum37/1...-solution.html

    As noted before, care should be taken with the caustic sodium hydroxide:
    http://www.ccohs.ca/oshanswers/chemi...hydroxide.html

  4. #34

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    LS-1c, post 28, is now 14 months old. Since the 6 months report above it developed 2 more films and was then left in a half full glass bottle.
    At 14 months I developed a test film , it came out very thin, barely visible images, except for slight darkening of the film leader.
    The pH was originally 10.4, after 3 months 9.9, after 6 months 9.7, now after 14 months 9.6.
    It has gone inky black, even stains the stop bath.
    Inky blackness is usually associated with p-aminophenol oxidation products so I suspect that all the ascorbate is oxidized and some of the aminophenol as well.
    Hence it is suggested that the shelf life be considered as 6 months only.

  5. #35

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    P-aminophenol and metol are very similar as developing agents. Unlike metol p-aminophenol does not cause allergic dermatitis. The problem with p-aminophenol is its instability in air. It rapidly oxidizes in crystalline form and is thus only used in liquid developers like Rodinal. The hydrochloride salt has greater stability than the free base but is still less stable than metol. The main difference between the two developing agents is that p-aminophenol is a bit softer working than metol and produces somewhat less contrast when used in typical developer formulations like D-76 or DK-50.
    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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