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  1. #1

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    Making metaborate (again)

    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.

    Quote Originally Posted by Mike Wilde View Post
    I am pretty sure that I saved this from a Pat Gainer post.

    Anyways - away we go...

    The biggest problem I have faced when mixing metaborate is how pure is the hydroxide? It will absorb humidity and carbonic gas, so it's weight/activity will change as it ages. So, when one mixes the traditional borax/hydroxide formula, the results may vary significantly.

    After lots of experimentation, I've devised the following to be able to mix it without the help of a pH meter: The trick is to make a concentrated solution, and mix it in a clear glass container (the concentrate will give visual clues).

    25% metaborate solution (as per Michael Gudzinowicz tetrahydrate formula):
    Water (room temp - some 20C/68F) - 400cc
    Sodium hydroxide - 19g (pour slowly, stirring; usual precautions apply)
    Borax - 90g (pour slowly, stir until dissolved, may take a couple of minutes).

    Two things may happen:
    -If the hydroxide is pure, there will be no borax left and the solution will be clear when stirred. And there will be no metaborate (transparent) crystals in the bottom.

    -If the hydroxide is not pure (my case), there will be borax left, the solution will be cloudy when stirred, due to being a mix of dissolved metaborate and un-dissolved borax.

    Start to add hydroxide slowly, stirring, 1g a time (or the equivalent in cc of an 20~50% hydroxide solution, easier) until the solution clears

    When standing and there are just some borax crystals in the bottom of the solution when not stirred. DO NOT OVERDO.

    If the crystals loose the borax whitish look and become kind of transparent (metaborate crystals), you've overdone the hydroxide, and the solution pH will be higher than it should be.

    This is like a titration in which borax is the indicator. Let it stand for a couple of minutes (decant) and slowly pour the liquid in another container. Do not pour the crystals that are at the bottom.

    Add water to 500cc.

    This 25% solution has been mixed more than once, and it passes the basic (ouch!) test - dilute it to 1% and pH is 11.1 (within my pH meter precision). I've frozen it to 0C/32F and left it stand for 2 days at room temp and no crystallization.
    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 ...)
    Last edited by pdeeh; 09-23-2013 at 08:10 AM. Click to view previous post history.

  2. #2
    Thomas Bertilsson's Avatar
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    Are you doing this to be able to do 2-bath developing, a la Barry Thornton?
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  3. #3

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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. #4
    Thomas Bertilsson's Avatar
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    Quote Originally Posted by M Stat View Post
    Seems like a lot of trouble for something that can be ordered from either Photographer's Formulary or Bostick and Sullivan.
    Did you see the last line of the OP's comments? They are not in the US.
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  5. #5

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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. #6

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    Quote Originally Posted by Thomas Bertilsson View Post
    Are you doing this to be able to do 2-bath developing, a la Barry Thornton?
    No I'm not, but I have read Michael R's thread about divided developers

  7. #7

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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.
    Last edited by Gerald C Koch; 09-23-2013 at 11:49 AM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  8. #8
    Rudeofus's Avatar
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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.
    Trying to be the best of whatever I am, even if what I am is no good.

  9. #9
    Thomas Bertilsson's Avatar
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    Maybe contacting someone like Wolfgang Moersch might help too? He's usually very helpful.
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  10. #10
    Rudeofus's Avatar
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    Quote Originally Posted by Thomas Bertilsson View Post
    Maybe contacting someone like Wolfgang Moersch might help too? He's usually very helpful.
    You do realize that the Fototechnik Suvatlar link I posted above sits directly on Moersch's web page, yes?
    Trying to be the best of whatever I am, even if what I am is no good.

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