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Thread: In old developer formulas, how do you know the concentration of reagent called for?

  1. #1

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    In old developer formulas, how do you know the concentration of reagent called for?

    I'm looking at some old developer recipes and they're frustratingly non-specific. They often call for either acetic acid or nitric acid, yet give no indication of what concentration they want 4 drachms of (nor, for that matter, what concentration they want 10 drops of nor how big they consider a drop to be!).

    Is there an "alchemy to proper modern science" decoder ring available anywhere?

  2. #2

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    Re: In old developer formulas, how do you know the concentration of reagent called fo

    Glacial acetic acid is 99%... (You won't find the acids in developers, but stop and fix...)

    Cross check different formulas in other books/listings (as many are close or the same) for errors or more clarity... The "recipes" are very close!!!

    There is a weight correction for anhydrous (desiccated) or monohydrated dry chems... After about the 30's/40's, most of the formulas were well standardized, the big difference was weight and liquid volume due to English to metric amounts...
    (An old "Photo Lab Index" section on "conversions" will help...)

    Good luck!!!


    Steve K

  3. #3

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    Re: In old developer formulas, how do you know the concentration of reagent called fo

    I'm looking at formulas from the late 1800s, so a lot of them do have nitric, acetic, or both in the developers. It's quite frustrating, having a hard science background, to deal with stuff like this that isn't explicitly clear.

  4. #4

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    Re: In old developer formulas, how do you know the concentration of reagent called fo

    Quote Originally Posted by williaty View Post
    I'm looking at formulas from the late 1800s, so a lot of them do have nitric, acetic, or both in the developers. It's quite frustrating, having a hard science background, to deal with stuff like this that isn't explicitly clear.
    There are some acid salts in some very old developers, but most developers are alkali accelerated...

    Most silver stuff will develop in almost any developer to some degree, but to completion if long/short enough...

    I understand, information before the 1870's gets archaic, but it was not at all exact rocket science back then, so a lot of slop factor... ;-)

    Common sense and testing will guide you (and take notes)...

    Steve K

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