Ammonium Thiosulfate or Sodium Thiosulfate

hka · Oct 14, 2007

Is it possible to use Ammonium Thiosulfate instaed of Sodium Thiosulfate as Hypo in Farmer's reducer??
What about the conversion rate??
At the moment I have Ammonium Thiosulfate 58-60% liquid on the shelf.
I do need 120 grams of Sodium Thiosulfate and water to make 500 ml.
How much Ammonium Thiosulfate (in ml) do I have to add to make also a stock solution of 500 ml?

Michel Hardy-Vallée · Oct 14, 2007

In theory, I would say yes, given that ammonium thiosulfate is a reducer in an acidic solution, much more so than sodium thiosulfate. That's why one should not over-fix with rapid fixer, otherwise you lose densities.

As for the practical side, er, sorry, no idea! I just read books but I don't apply their knowledge

Ian Grant · Oct 14, 2007

Try a 10% solution Harry and test it on some scrap prints. 50g/litre.

Maybe start with a solution slightly more dilute than when using Sodium Thiosulphate.

Ian

Photo Engineer · Oct 14, 2007

Ammonium thiosulfate mixed with ferricyanide is so powerful, it becomes a rapid, one-shot blix. You could totally remove your image without wanting to. I suggest careful trials.

PE

dancqu · Oct 15, 2007

hka said:
Is it possible to use Ammonium Thiosulfate instaed
of Sodium Thiosulfate as Hypo in Farmer's reducer??

I'd be careful with that. Potassium ferricyanide itself
is and oxidizer. It oxidizes elemental silver into silver
ferrOcyanide. What it will do to ammonia I couldn't
say. You could do as some others and fix after
the "bleach". The fix is the "bleach". Dan

Photo Engineer · Oct 15, 2007

Dan;

It is safe to mix ammonia with ferricyanide, but ferricyanide is an oxidant and thiosulfate is a reducer. These mutually react and the solution decomposes. In addition, they both react with silver metal and dissolve it utterly.

It is a coin toss as to which takes place first. Usually, the silver goes then the rest of the reactants mutually destruct.

PE

georgegrosu · Oct 15, 2007

Harry,
for fixer I use normal a Kodak formulas for ECN 2. (http://www.kodak.com/US/en/motion/support/processing/h24.shtml module 7 - Process ECN-2 Specifications - FORMULAS AND ANALYTICAL SPECIFICATIONS - Fixer). I use this solution for b/w or color films. Is a fast fixer. When you use Sodium Thiosulfate pentahydrate, the concentration is 200 – 250 g/1000 ml of solution for fixer.
With Ammonium Thiosulfate (solution 58 %) you can use 185 ml/1000 ml fixer.
Is good if you use sodium sulfite in the fixer because this component stops the reaction:
Na2S2O3 = Na2SO3 + S (colloidal) for Ammonium Thiosulfate the reaction is similar, but is much complicate for write.
Normal, I use two fixer: first – used and second fixer – fresh.

George

georgegrosu · Oct 15, 2007

Sorry,
I have same problems with the Kodak link.

George

dpurdy · Oct 15, 2007

Isn't the regular Kodak rapid fix Ammonium thiosulfate? I have been using that with Potas ferricyanide to bleach prints for a million years. Or at least 20.

hka · Oct 16, 2007

Thanks. I will give it a try.

georgegrosu · Oct 16, 2007

When I want to bleach (total) prints I use the bleach formula from ECN 2 process (potassium ferricyanide .. 40 g and sodium bromide ….. 25 g all for 1000 ml solution. After a good wash go in the fixer. In this case, you can have a good control of process (solution with constant proprieties) that a singe solution (have a little life of work). If you want only reducer a little of general density of the print I think this option is good if you use a dilution 1:5 for bleach solution.
For b/w negatives, I use only potassium ferricyanide (1.5 – 2.5 g/ 1000 ml) and after a good washing the film go in the fixer. The speed of silver dissolving, in this case, is little without sodium bromide.
I thing that the reducer with a single solution have same unknown finish.

George

hka · Nov 4, 2007

Today I did some experiments with my homebrew Reducer with Ammonium Thiosulfate. As Ian said start with 10% stock solution. With this in mind I made some testprints. Started with a very diluted version with 2,5 ml Solution A and 12,5 ml Solution B at 1 liter water, souping the print for 30 seconds was quite right. This gave me an 0,05 density reducing in the highlights just enough to give it that sparkle I needed.

Ammonium Thiosulfate or Sodium Thiosulfate

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