Kodak SH-1 Formalin Hardener for Films and Plates

Kodak SH-1 Formalin Hardener for Films and Plates

  1. FilmIs4Ever

    FilmIs4Ever Member

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    FilmIs4Ever submitted a new resource:

    Kodak SH-1 Formalin Hardener for Films and Plates - Kodak SH-1 Formalin Hardener for Films and Plates

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  2. Photo Engineer

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    Common Formalin is actually about 37% and the formula I have contains 50 - 100 g/l of Sodium Sulfate.

    PE
     
  3. FilmIs4Ever

    FilmIs4Ever Member

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    Hey, Ron, so would that require an adjustment of this formula? I assume that they either got lazy and rounded it to 40% or the concentration may have been changed since this was published in 1947.
     
  4. Photo Engineer

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    Actually, my formula used 10 ml/l of 37% formalin and the pH was stated to be 9.5 - 10.1 in the formulas I have in my notebook here.

    PE
     
  5. FilmIs4Ever

    FilmIs4Ever Member

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    So is the pH for the SH-1, or the formalin soln. you add to it? As is indicated, the formula I have is originally in U.S. Customary, so it's possible they just carelessly rounded to the nearest half fluid dram when they converted it from a formula originally written in cgs units, which accounts for the shift down when I converted back. IIRC, it was actually somewhere in between 9.75- and 10mL, and I just rounded to the nearest 250µL. I'd assume that the formalin is actually the same in both cases and they just rounded to 40% in the book I have. Converting the amount in a 40% solution to 37% gives about 10.5mL equivalent so that isn't the reason for the difference in the amount. Again, it's probably a matter of my formula having less exact rounding than yours does.

    Is the Na-Sulfate in addition to- or as a replacement for the Sodium Carbonate.

    I've noticed that there are more than a few examples of Kodak formulae, published by Kodak or allegedly taken straight from Kodak that are modified over time, without any indication.
     
  6. Photo Engineer

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    The pH of the hardener should be alkaline and varies slightly due to the fact that unstabilzed formalin can oxidize to form formic acid as a contaminant. This causes some variation in pH. I used to adjust the pH to the pH of the developer I was using.

    The sulfate is in addition, not in place of carbonate as the solution should be buffered with an alkali.

    The hardener I refer to may be a different formula number, it is just the preferred one we used in-house.

    PE