Making metaborate (again)

Discussion in 'B&W: Film, Paper, Chemistry' started by pdeeh, Sep 23, 2013.

  1. pdeeh

    pdeeh Member

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    As Sodium metaborate (Kodalk) now seems almost impossible to buy in the UK (Silverprint no longer carry it and enquiries to those chemical suppliers who will deal with private individuals have drawn a blank), I have resorted to brewing my own using the instructions Mike Wilde gave in a post at APUG in 2007, which I'll quote in full below.

    Using this has prompted a few questions for me which I would like to clear up - I stopped learning chemistry in about 1974.

    I also know that one can substitute Borax and Sodium hydroxide directly into formulae (although there seem to be variations in the weights and proportions given in the various posts I have found here and elsewhere) but as Mike Wilde points out, one never knows the purity of the hyroxide (or I suppose the Borax, but that doesn't seem to concern folk so much?); plus hydroxide seems to absorb atmospheric water very readily indeed, so presumably that will also change the purity and thus weights and proportions?

    My questions fall into two areas.

    First, relating to mixing the solution as Mike Wilde outlines:

    I use Sodium hydroxide bought on the high-street marked as 98% w/w, and Borax bought from a chemical supplier via eBay (it is almost impossible to purchase Borax otherwise in the UK); I
    use deionised water

    1. When he says "until the solution clears", is this to the point where it is "gin clear" or to the point where it's "mostly clear but vaguely milky still" or what? The solution I've just made has been standing for 20 minutes: there are a few grains of what look like Borax at the bottom of the vessel, and some sort of soft white wispy product has risen to the top of the solution. In between, the solution has that slightly translucent look one sees in (say) D76 stock.

    Remember IANAC ...

    2. I seem to have to add a LOT of additional hydroxide to get the solution to clear - perhaps 2 to 3 times the starting weight of 19g. I have no idea of course whether this is to be expected or not.

    3. If I do go "too far" and start getting the translucent metaborate crystals forming, how badly off might the pH then be to be and how detrimental to the working of any formula might that make it (another piece of string question I know, but if it's .5 off that's rather different to being 2 off I assume)

    Secondly, relating to substituting Borax and hydroxide separately into developer formulae:

    4. For the purposes of the home hobbyist making the odd litre of developer, will the purity of the hydroxide really make much difference?
    I do understand that developers are formulated to particular pH ranges, and that one cannot expect them to work as designed if the pH varies wildly from that expected.
    But if I use hydroxide that's been in its plastic bottle under my sink for 18 months, am I likely to go terribly far wrong? (Yes, I realise the most likely answer to this question is "It depends ...")


    (Please remember I'm in the UK, so it's not going to help me to say "You can buy metaborate from the Formulary for $5/lb", because I can't ...)
     
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  2. Thomas Bertilsson

    Thomas Bertilsson Subscriber

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    Are you doing this to be able to do 2-bath developing, a la Barry Thornton?
     
  3. M Stat

    M Stat Member

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    Seems like a lot of trouble for something that can be ordered from either Photographer's Formulary or Bostick and Sullivan.
     
  4. Thomas Bertilsson

    Thomas Bertilsson Subscriber

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    Did you see the last line of the OP's comments? They are not in the US.
     
  5. M Stat

    M Stat Member

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    Although Bostick and Sullivan will not ship hazardous materials overseas, Sodium Metaborate is not a hazardous material, therefore they will ship it.
     
  6. pdeeh

    pdeeh Member

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    No I'm not, but I have read Michael R's thread about divided developers :smile:
     
  7. Gerald C Koch

    Gerald C Koch Member

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    As a chemist I can say that the only reliable way to make sodium metaborate from borax and lye is to have an accurate scale and weigh out the two chemicals. Mike Wilde's method is subjective and may not produce a product that is useful. It is preferable to buy this chemical if possible to avoid dealing with sodium hydroxide which is a dangerous chemical capable of causing severe burns.

    One of the uses of metaborate in photographic formulas is as a buffering agent. It is important that there is no excess sodium hydroxide in the product.

    Sodium hydroxide will absorb carbon dioxide and water from the air if not stored properly. This will reduce it's alkalinity.
     
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  8. Rudeofus

    Rudeofus Subscriber

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    Let me be the first one here to suggest Fototechnik Suvatlar as a EU based source for Sodium Metaborate (and many other useful compounds) in photographic quality. He speaks English and AFAIK ships (at least) EU wide.
     
  9. Thomas Bertilsson

    Thomas Bertilsson Subscriber

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    Maybe contacting someone like Wolfgang Moersch might help too? He's usually very helpful.
     
  10. Rudeofus

    Rudeofus Subscriber

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    You do realize that the Fototechnik Suvatlar link I posted above sits directly on Moersch's web page, yes?
     
  11. Thomas Bertilsson

    Thomas Bertilsson Subscriber

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    No, I didn't. If I did, perhaps I wouldn't have posted the suggestion, yes?

    I was just trying to help.
     
  12. Alan Johnson

    Alan Johnson Subscriber

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    Also note there are two forms of sodium metaborate, -4mol and Kodalk. Silverprint used to sell Kodalk.
     
  13. pdeeh

    pdeeh Member

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    Yes, as I said in my OP:

    Regarding 4-mol and 8-mol, I have read posts here at APUG that suggest it is of no importance which is used for photographic work.
     
  14. john_s

    john_s Subscriber

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    Which version you have will affect the amount needed, as one contains more water of crystallization.
     
  15. Alan Johnson

    Alan Johnson Subscriber

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  16. Tom1956

    Tom1956 Inactive

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    Wow, this is enlightening. Never had an inkling that sodium metaborate could be so confusing. It would seem the moral of the story is to always use Kodalk, and hope the publisher of whatever formula you're using had it in mind.
     
  17. paul_c5x4

    paul_c5x4 Subscriber

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    Oh bu***r. I had it on my list of stuff for the next order. Will have to try other sources...
     
  18. Gerald C Koch

    Gerald C Koch Member

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    Sodium metaborate is not any different from any other chemicals. You must know the hydration form called for in the formula. Another example would be sodium carbonate -- anhydrous or monohydrate? Unfortunately many formulas are not written in a very accurate form.
     
  19. Rudeofus

    Rudeofus Subscriber

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    The confusion comes from the fact that tetrahydrate can mean two different forms of hydration (NaBO2 * 4 H2O and Na2B2O4 * 4 H2O), something which is not an issue with most other compounds including Sodium Carbonate. The Xtol Concentrate thread referenced by Alan Johnson sheds some light on this.


    @Alan: Moersch does sell Sodium Metaborate through Fototechnik Suvatlar, see my previous post here in this thread.
     
  20. Gerald C Koch

    Gerald C Koch Member

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    There are 3 hydration forms of sodium metaborate' as evidenced by 3 CAS numbers

    Anhydrous (NaBO2) CAS 7775-19-1
    A dihydrate (NaBO2.2H2O or as Na2B2O4.4H2O ) CAS 16811-11-6
    A tetrahydrate (NaBO2.4H2O or as Na2B2O4 .8H2O) CAS 10555-76-7

    Things are made rather confusing by representing the anion in two different forms BO2- or as B2O4-2. Once the anion is represented the same way it is easy to see the different forms.

    The tetrahydrate converts to the dihydrate above 53.6C (128F).
     
    Last edited by a moderator: Sep 27, 2013