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  1. #31

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    Quote Originally Posted by dancqu
    The IPI gives reasons for the use of polysulfide rather than
    sodium sulfide. None of those reasons has anything to do with
    sodium sulfide's effectiveness as an archival treatment. They
    do not spell out their reasons for mentioning the polysulfide.
    Drum quantities is likely a factor, manufacture, and S&H
    are likely others.

    They do say that sodium sulfide affords complete archival
    protection at a 1:9,999 strength; 0.01%. in solution. Dan
    Various publications written by IPI people clearly describe why polysulfide is more preferred in practice. Plain sodium sulfide is good for lab testing as a comparison sample but it is very hard to use in practice because the solution is very unstable and has very small processing capacity. Strong polysulfide solution is a lot more robust, practical way to approach this problem in darkroom.

  2. #32

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    Quote Originally Posted by Ryuji
    Various publications written by IPI people ...
    Plain sodium sulfide ... is very hard to use in practice
    because the solution is very unstable ...
    Very unstable! Gosh! You don't suppose it'll explode?

    I'm not going to debate the sulfide vs polysulfide issue.
    The reason; we are approaching the issue, each with our
    own objective in mind for one or the others use.
    I may or may not be interested in toning but I am
    interested in LE.

    Various publications; search Google for, stability black white .
    At the very top, an Abbey Newsletter. Most central to this
    debate is the section on sulfideing. Readers will have to
    make up their own minds. I've read and now have a
    couple of sulfide solutions being time tested. Dan

  3. #33

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    Quote Originally Posted by dancqu
    Various publications; search Google for, stability black white .
    At the very top, an Abbey Newsletter. Most central to this
    debate is the section on sulfideing. Readers will have to
    make up their own minds. I've read and now have a
    couple of sulfide solutions being time tested. Dan
    Read that, and also key research reports mentioned in that paper.

    Very dilute sodium sulfide solution is very unstable and does not keep.
    Very dilute polysulfide is also a good agent for protecting prints
    from oxidative attacks but has the same problem of very small processing capacity and short life. That is, polysulfide toner is also unstable if kept in dilute solution. This is one reason
    IPI Silverlock is very concentrated.

    There is an IPI Q&A section in RLG Preservation Handbook. If you don't believe me, that's probably the easiest source to get the same words from IPI. Their report to National Endowment for Humanities is also an essential reading. Unfortunately these good info are available on print only and not on the internet.

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