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  #1  
Old 24th July 2022, 06:47 PM
Nat Polton Nat Polton is offline
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Default Home made Kodalk

I am getting to the end of my Kodalk (Sodium metaborate.)

I have a formula to make my own shown below.

7g Borax mixed into 300ml water
1.5g Sodium Hydroxide
Top up to 400ml with water

40ml = 1g Sodium metaborate.


All seems OK until you consider I am making 500ml of TF-2 Alkaline Fix that requires 5g of Sodium metaborate. At 40ml = 1g that is 200ml to be added to the first amount of luid of 300ml fluid.
To much liquid.

So how concentrated can I mix the Sodium Mtaborate stock solution?

Cheers.
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Old 25th July 2022, 05:33 AM
Stocky Stocky is offline
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The limiting factor would appear at first to be the solubility of borax. A search will offer various amounts, and warmer temperatures will allow more to dissolve. Sodium hydroxide is very soluble (And Dangerous Especially When in Dissolving in Warm Water).
I have a vague memory of an article at APUG (Photrio I think it's now called) where it didn't all need to be dissolved at first. I'll have a look.

I haven't tried to make metaborate this way. My only reservation would be that the hydroxide is so powerful that an error in weighing might leave the mixture too alkaline. This could happen if, for example, your borax had absorbed atmospheric water and was consequentially effectively a bit less in real quantity. Checking the pH would be helpful.

My wife says I'm often negative. I guess that's right.
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Old 25th July 2022, 02:30 PM
Mike O'Pray Mike O'Pray is online now
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Quote:
Originally Posted by Nat Polton View Post
I am getting to the end of my Kodalk (Sodium metaborate.)

I have a formula to make my own shown below.

7g Borax mixed into 300ml water
1.5g Sodium Hydroxide
Top up to 400ml with water

40ml = 1g Sodium metaborate.


All seems OK until you consider I am making 500ml of TF-2 Alkaline Fix that requires 5g of Sodium metaborate. At 40ml = 1g that is 200ml to be added to the first amount of luid of 300ml fluid.
To much liquid.

So how concentrated can I mix the Sodium Mtaborate stock solution?

Cheers.
Nat, sounds like a question for John Finch at Pictorial Planet

Worth asking him as I got a very quick answer on my "missing video"

Mike
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Old 25th July 2022, 03:18 PM
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GoodOldNorm GoodOldNorm is offline
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Pictorial Planet aka John Finch has a video on YouTube on how to make sod. Metaborate
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Old 25th July 2022, 09:11 PM
Mike O'Pray Mike O'Pray is online now
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Nat, I have just had a look at John's Finch's "Making TF-2 Fixer" video where he mentions the difficulty of obtaining sodium metaborate and he simply suggests that you add the borax and sodium hydroxide powders straight into the rest of the ingredients when making TF-2

He doesn't seem to suggest the need to do this in any particular order so on the surface it would appear that at the stage when metaborate powder is added you simply substitute the borax and sodium hydroxide, presumably in the same order in which you make up "liquidised" sodium metaborate

So it might be my naivety but might the process be simpler than you think

On the other hand I may be missing something in what you see as a problem

Mike
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Old 25th July 2022, 10:16 PM
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See
https://youtu.be/kPrVqgDN9Z0
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Old 26th July 2022, 01:37 PM
Lostlabours Lostlabours is offline
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Borax comes in different forms Anhydrous, Dihydrate, and Pentahydrate. We use the Anhydrous form usually here in the UK.

Be aware that Borax in hardware stores now is often marked in smaller print "Substitute" and is Dodium Sesquicarbonatehas no photographic use.

It's easier to think:

10g Sodium Metaborate = 7g Borax (anhyd) + 1.5g Sodium Hydroxide.

Ian
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Old 26th July 2022, 09:24 PM
Stocky Stocky is offline
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Now that I think about it, my reservations about getting the combination exactly right, because of the strength of sodium hydroxide, for fixer it would be inconsequential, as the pH could vary a bit without the slightest problem.

For a developer I think it would be more important to get it right.

This is the article I was thinking of. Unnecessarily complicated in the present context.

https://www.photrio.com/forum/thread.../#post-2458262

Last edited by Stocky; 26th July 2022 at 09:33 PM. Reason: addition
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Old 26th July 2022, 11:03 PM
Mike O'Pray Mike O'Pray is online now
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Quote:
Originally Posted by Lostlabours View Post
Borax comes in different forms Anhydrous, Dihydrate, and Pentahydrate. We use the Anhydrous form usually here in the UK.

Be aware that Borax in hardware stores now is often marked in smaller print "Substitute" and is Dodium Sesquicarbonatehas no photographic use.

It's easier to think:

10g Sodium Metaborate = 7g Borax (anhyd) + 1.5g Sodium Hydroxide.

Ian
Ian, now you're here can I ask: Is there any reason why Nat cannot simply mix the borax and sodium hydroxide powders in with the rest of the ingredients when he makes the fixer.

If he can does he do it in the order in which he would add the sodium metaborate powder were that to be available ?

Thanks

Mike
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