Percentage solutions

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darkroommike
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Percentage solutions

Post by darkroommike » Sun Dec 31, 2017 8:08 am

[Forgive me for sticking this in the FILM development forum but I don't see a forum on black and white PAPER developers.]

What are the common "best" percentage solutions for developers additives, e.g.
  • 10% Potassium bromide
  • 6% Sodium Carbonate
  • 0.2% BZT (benzotriazole)
Am I missing any, what about having Potassium Carbonate as well as Sodium Carbonate?

And if I were to make a percentage solution of Phenidone what is the current thinking on the best solute?

Thanks, and Happy New Year!
Mike

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sanchell
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Re: Percentage solutions

Post by sanchell » Mon Jan 01, 2018 6:43 pm

Darkroom Mike. Probably Enlarging and Printing would have been a better place for this, Darkroom Mike. But hey, who cares? We're just a bunch of guys and gals trying to share what we know.

You've listed the three most commonly used percentage solutions. These are the three I list in the DCB.

Edwal used to recommend a 9% solution of sodium sulfite as an additive to FG-7 for finer grain, at the expense of sharpness, but I don't know of anyone else who recommends this.

You've specifically asked for % solutions for developer additives. However, anything can be made and used in a % solution and I give a full explanation on how and why on page 190 of the DCB, 4th ed. Most people don't bother but it makes a lot of sense. Even developing agents can be made into percentage solutions if they are properly preserved. An example would be ABC Pyro or any two-solution developer.

Phenidone is the perfect candidate for a % solution as it is used in such small amounts it is a pain to measure out each time. I usually dissolve it in water to make a 1% solution by mixing 10 g of Phenidone in a liter of water.

Crawley's classic FX 37 formula uses 0.5 g of Phenidone. It is far easier to measure out 50 ml of the 1% solution to use in a liter of FX 37 than trying to accurately weigh 0.5 g each time.
Do it in the Dark,



Steve Anchell

darkroommike
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Re: Percentage solutions

Post by darkroommike » Tue Jan 02, 2018 7:05 am

OK, revealing my real age, Jason Schneider used to recommend using a sulfite solution for diluting Rodinal, his "precise measure" was a level "Chock Full of Nuts" coffee scoop.

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sanchell
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Re: Percentage solutions

Post by sanchell » Tue Jan 02, 2018 12:05 pm

sanchell wrote:
Mon Jan 01, 2018 6:43 pm
Crawley's classic FX 37 formula uses 0.5 g of Phenidone. It is far easier to measure out 50 ml of the 1% solution to use in a liter of FX 37 than trying to accurately weigh 0.5 g each time.
I've just been corrected by Bill Troop on this. Rather than trying to paraphrase what he said here is what he sent me in an email:

"If you really want to use phenidone, then you need to get a microgram scale (which is not that expensive anymore) and weigh out the tiny amounts you need. Yes, it's a pain, but it's the only certain way to make sure your phenidone will give you the activity you require. I will discuss in more detail some of the solutions that have been proposed, but I don't like any of them. These guys have this attitude: 'I want a phenidone percentage solution. Everyone says it's a problem. There ought to be a solution. I'm sure there's a solution.' Well, there isn't.

"It is deeply complicated by the fact that the reaction products of going-bad phenidone work so strongly with HQ, which in a sense revives the declining chemical. It's a mess.

"There's only one right way to work with phenidone. Buy it fresh, use it fresh.

"For the other chemicals you mention, water is an adequate solvent, though things like BZT can be tricky."
Do it in the Dark,



Steve Anchell

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