Sodium carbonate solution - how long does it keeps?

Discussion in 'Darkroom Developing and Printing' started by Jorge Omar, Jul 16, 2003.

  1. Jorge Omar

    Jorge Omar Guest

    If one split a developer in active part/carbonate, for how long will
    the carbonate solution keep (normal usage - bottle starts full and
    goes empty with usage).
    I understand that slowly carbonate will become bicarbonate.
    Would adding sulphite help? Does it changes pH?


    Jorge Omar, Jul 16, 2003
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  2. Jorge Omar

    dr bob Guest

    Sodium carbonate is the bottom of the line as far as oxidation is concerned.
    That indicates that there should be no deterioration in storage. I wouldn't
    worry about it. However the material is so cheap and available, I see no
    point is long term storage. When preparing my developer, I dump all the old
    and start everything from scratch. That way there is never a question as to
    when, what, where.

    It would be advisable to dump used solutions after use as the carryover of
    developer will eventually render the carbonate solution a little "hot" and
    the advantage of the two solution technique will be lost.

    Truly, dr bob.
    dr bob, Jul 16, 2003
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  3. Jorge Omar

    John Guest

    I think he means split stock and not divided development. Of course I
    agree that carbonate will keep a very, very long time either in solution or dry.
    If making a stock solution one does need to be aware of it's solubility though.
    Carbonate can precipitate out of solution to form something like crystals in the
    bottom of the bottle.

    John, Jul 16, 2003
  4. Jorge Omar

    Jorge Omar Guest

    Yes, it's to split a developer and not for two bath development.

    Reason for the question is 'cause I found two times in the NET - 3
    months and one year.
    Very coherent...


    Jorge Omar, Jul 16, 2003
  5. Jorge Omar

    John Guest

    Can you give me some more details on exactly what you are contemplating ?
    Something like FX-2 ?

    John, Jul 17, 2003
  6. Jorge Omar

    Jorge Omar Guest


    About 20 yrs ago (in another photo life) I've used the better part of
    an HC-110 bottle at a dillution of 1+63 (concentrate) plus carbonate
    (1g/L) and benzotriazole (1cc/L of 1% solution).

    I'm testing TMX with this soup (it becomes kind of compensating) to
    see if I can tame blown higlights.

    The reason for the question is if carb solution keeps a short time, I
    would mix less.

    Looks like I do not have to worry about keeping properties.

    Jorge Omar, Jul 17, 2003
  7. Jorge Omar

    John Guest

    Highlight contrast is mostly effected by the length of the development and
    to a lesser extent the activity level of the developer. Dilute your working
    solution a little more (1:74) and/or shorten your development time in 5%
    increments until you get the contrast under control.
    No, you don't.

    John, Jul 18, 2003
  8. Jorge Omar

    Jorge Omar Guest

    Thanks, John.

    I will start by lowering dev time (first test was 8 min @20C).

    Jorge Omar, Jul 18, 2003
  9. Sodium Carbonate slowly absorbs carbon dioxide from the
    air which lowers its pH. However, this is a slow process and
    for a strong concentration of carbonate in a closed
    container I think is not a practical problem. I think such a
    solution will keep for many months, perhaps much longer.
    Richard Knoppow, Jul 18, 2003
  10. Jorge Omar

    John Guest


    Do you remember anything about carbonate affecting the glass ? I have a
    vague memory of seeing glass "frosted" by carbonate stock after it had sat for
    some time on the shelf.

    John, Jul 19, 2003
  11. Jorge Omar

    John Guest

    Actually I was just wondering what it's reacting with. I'm sure that the
    reaction is slight as I only noticed the etching around 6 months after I mixed
    the stock. Do note that carbonate is used in the production of most glasses.
    Also I found the following in a search ;

    " In water, especially salt water, the Na and K carbonates in unstable glass may
    leach out, leaving only a fragile, porous hydrated silica (SiO2) network. This
    causes the glass to craze, crack, flake, and pit, and gives the surface of the
    glass a frosty appearance."


    John - Photographer & Webmaster -
    John, Jul 19, 2003
  12. Hydroxide ions in solution will etch glass very slightly. It's just a
    reaction with the SiO2 in the glass that produces soluble silicates. One
    of the most common methods of cleaning glassware in chemistry labs is to
    soak it in a concentrated solution of potassium hydroxide in alcohol (we
    call them "base baths"). This pulls off a very thin layer of glass as
    well as the grime. We don't use this technique for delicate parts or for
    fritted glass, for obvious reasons. Glassware left in a base bath for
    weeks or months typically gets "frosty", as you describe.

    In lab settings, alkaline solutions are never stored long-term in glass
    because the reaction with glass changes the pH (slightly) of the
    solution. The change is enough to mess up analytical results
    (titrations, etc.). Plastic bottles (Nalgene, usually) are used for
    these purposes.

    The carbonate in glass is likely immobilised in the glass structure
    and/or could react with the silica at the high temperatures of the
    glass-making process to produce something else. Someone correct me on
    this if I'm wrong.

    Hope this helps

    Jordan Wosnick, Jul 20, 2003
  13. Carbonate will slowly dissolve glass. This is why old
    books recommend against keeping carbonate in a jar with a
    glass stopper. Eventually the carbonate will weld the
    stopper to the bottle making it extremely difficult to
    For practical purposes there is no problem, the
    dissolution is very slow.
    Richard Knoppow, Jul 22, 2003
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