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  #1  
Old 17th November 2011, 08:31 AM
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Default Sodium metaborate

Hello all.

Yesterday I tried to develop my first roll in a two bath developer (test roll, nothing important in it). As David suggested me, I prepared a first bath with the metol and sodium sulfite and a second bath with sodium metaborate. But something didn't work. The film was Rollei RPX 100; did 5 min + 4 min.

My first idea is that I didn't mix properly the sodium metaborate. I didn't have the sodium metaborate in powder but I mixed it from borax and sodium hydroxide this way

75 grs borax + 15 grs hydroxide + 600 grs water

Do you think I mixed it wrong?
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  #2  
Old 17th November 2011, 09:45 AM
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Hi Domingo,

The formula that I have for a substitute to Sodium Metaborate is 125 Grams of Borax into 25 grams of Hydroxide plus 800 ml of water which is then topped up to 1000 ml. You have to add the Hydroxide to the water first and then add the Borax. However, I must stress that I have never used this as I always buy Sodium Metaborate. I also believe that it has a lower PH than Metaborate so would require extended development times.

What did not work when you developed the film in the two-bath developer? No image?, thin image?, flat image?, or . . .?
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Old 17th November 2011, 11:55 AM
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Hello David. Thanks for your interest.

Quote:
[...]
The formula that I have for a substitute to Sodium Metaborate is 125 Grams of Borax into 25 grams of Hydroxide plus 800 ml of water which is then topped up to 1000 ml.
[...]
yes, this is what proportionally have prepared; I only need 600 ml to develop one 120 roll.

I stock an excess of sodium hydroxide, so I'd like to try to prepare the sodium metaborate myself - even is possible I will learn something!

I'd make another approach this morning based in a message I've found in APUG. Since what I'm gonna develop is a 120 roll, I'd prepared 600ml this way: (2 grs water + 1.7 grs hydroxide + 8.4 grs borax) + 600 grs water

The 1.7 grs hydroxide didn't dissolve in the 2 grs water, but the water becomes hot; I stirred for about two minutes. As the citated APUG message explains, when I added the borax the ensemble began to react yielding a rock solid compound.

Then I added 200 grs hot water, the (I hope) metaborate dissolved without any problem. Finally, I added 400 grs water.

I'm gonna develop the film this afternoon.
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Old 18th November 2011, 08:18 AM
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Roll developed.

I'm still a novice evaluating developed film, but I feel negatives are quite fine this time. The second way I prepared the sodium metaborate worked well.

Sorry for the noise.
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Old 18th November 2011, 09:30 AM
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Sorry: I made a mistake with quantities in message #3.

The correct should be

(2.00 grs water + 1.08 grs hydroxide + 5.40 grs borax) + 600 grs water

My apologies.
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Old 18th November 2011, 10:32 AM
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This might be of interest. From the now-defunct website of Ryuji Suzuki, some notes about Kodalk (sodium metaborate).

<start of quote>

Kodalk or "Kodak balanced alkali" is Eastman Kodak Company's trade name for sodium metaborate. The largest supplier and research institution for this compound is U.S. Borax Research Corp. in Anaheim, California. In Ullmann's Encyclopedia of Industrial Chemistry, Robert A. Smith of U.S. Borax explains industrial production processes for this compound among other boron compounds in detail.

In old literature, sodium metaborate tetrahydrate (CAS 10555-76-7) is denoted Na2B2O4 - 8H2O. This lead to old nomenclature describing hydration of sodium metaborate to be octahydrate. However, as more modern techniques became available, the actual structure of sodium metaborate is known to be better described by NaB(OH)4 - 2H2O, and this substance became to be commonly denoted by NaBO2 - 4H2O, hence tetrahydrate. According to detailed catalogues of several laboratories chemical suppliers, there is no NaBO2 - 8H2O commonly traded today. Robert Smith of U.S. Borax explains that "sodium metaborate tetrahydrate is the stable solid phase in contact with its saturated solution between 11.5 and 53.6°C ." Therefore, octahydrate in old nomenclature and tetrahydrate in modern nomenclature indicate the identical chemical in the same hydration form. It is just that the nominal formula weight for tetrahydrate is half that of octahydrate. One mole of tetrahydrate would provide one mole of B(OH)4- in aqueous solution, while octahydrate would provide two moles.

The formula weight for this sodium metaborate tetrahydrate is 137.8. Common procedures for making sodium metaborate from borax and sodium hydroxide are often based on incorrect assumption that Kodalk is actually NaBO2 - 8H2O, and they have to be corrected. Fortunatelly, the proportion of mixture is correct, and the error is in final dilution, so solutions made from incorrect instruction can still be used, but by increased amount.

In order to make 1.0g sodium metaborate tetrahydrate, mix 0.692g borax and 0.145g sodium hydroxide. When dissolved in water, these two make solutions of identical composition.
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Old 26th May 2015, 06:28 PM
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Thought it might be worth digging this old thread out - if you are in the market for sodium metaborate it's probably much less painless to make it via the formulation above.

At Silverprint I learned the hard way that sod. metaborate has to be freshly produced & properly packaged and stored. We purchased 10 x 25kg bags from the principal UK supplier and lost most of it, the packaging was ineffective & it didn't last the year.

Switching to a more expensive chemical wholesaler who shall be nameless (but it begins with an 'A') we found they were incapable of supplying an effective metaborate. So we gave up at that point, the borax + sodium hydroxide is the route to follow.
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Old 27th May 2015, 08:51 AM
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Hi Martin,

Interesting! - I buy Sodium Metaborate (Natriummetaborat in German although the package label always has Natriummetaborat-tetrahydrat written on it) from the supplier Suvatlar in Hamburg in the quantity of 500g in plastic containers. This is sufficient for 42 litres of Bath B in Barry Thornton's two-bath developer. Now with a litre of Bath B being sufficient for 15 rolls of film and me making the developer for my own use and some of my students, I reckon that I make about 24 litres of Bath B per year. This means that I may well be using Sodium Metaborate that is over a year old to me plus however long it was stored by Suvatlar.

So to my question, what would I observe if the Sodium Metaborate is not effective as it should be? I do not seem to have any problems with using a year old Sodium Metaborate from a half opened container. Is this just luck or do Suvatlar supply an especially good grade of Sodium Metaborate or does the 'tetrahydrate' in the name written on the label mean that it is actually a different type of Sodium Metaborate.

It would be good to know the answer to this, not just for my students and I, but also to the very many people I have recommended BTTB developer to.

Bests,

David.
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Old 27th May 2015, 12:32 PM
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I also have found that sodium metaborate powder that I bought from Vanbar in Melbourne seems to last well (quite a few years, can't remember how many). I'm wondering about Martin's post above. perhaps it was a form that absorbed moisture from the air and became a solid mass, which can happen with a number of chemicals. Such compounds are the same thereafter except that their weight has changed which makes critical measurements problematical.

For the bath B of Barry Thornton's two bath I doubt that such inaccuracy would make much difference.
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Old 27th May 2015, 01:27 PM
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So would a ratio of 5:1 125g Borax to 25g Hydroxide made up to 1ltr of water be near enough for the second bath in Barry's 2 bath developer? Or does it have to be bang on 69.2g to 14.5g in 1ltr of water?
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