Substituting Ammonium Thiosulfate with Hypo?

[thedetective06]

Hello,
I've been wanting to develop ECN-2 from raw chemicals. Ammonium thiosulfate is quite hard to source here in small amounts, so I've been wanting to substitute it with Hypo. I know C41 & ECN-2 fixer (which uses Ammonium thio) works on B&W, but I'm wondering if it will work in reverse because of the thiosulfate ion. Will I just have to change the fixing time? Or will the pH be affected?

 

[koraks]

Welcome to Photrio!

Modern Kodak color negative films (including Vision 3) are at least in part based on T-grain technology. This means they'll fix out very, very slowly in a plain sodium thiosulfate fixer. You could try adding a bunch of ammonium chloride etc. to try and make a quasi-rapid fixer; this might work OK, esp. on the higher temperatures of a color negative process. However, I'd recommend trying to get some C41 fixer instead, which will be guaranteed to work.

 

[thedetective06]

Thank you, glad to be here!
What would be the problems caused by very slow development? Even C41 chems are quite hard to find here, and even then they are only sold in kit.

 

[mshchem]

I agree with Koraks. Sodium Thiosulfate would work, again quite slowly, you would need to watch to make sure it's fully fixed. Any rapid fixer for black and white, X-ray, graphic arts film is likely ammonium thiosulfate based, try this if you want.
Welcome to the forum!

 

[thedetective06]

Both Fujifilm XF-25 and Ilford Hypam/Rapid fixer are available here, but looking at their data sheets, they both contain acetic acid which will likely mess up the pH.

I did notice someone else was able to adjust the pH of rapid fixer back up to neutral, but I see they added ferric ammonium EDTA here. Do I also need it with a seperate bleach and fix?

I agree with Koraks. Sodium Thiosulfate would work, again quite slowly, you would need to watch to make sure it's fully fixed. Any rapid fixer for black and white, X-ray, graphic arts film is likely ammonium thiosulfate based, try this if you want.
Welcome to the forum!

 

[koraks]

What would be the problems caused by very slow development?

Of course, here we're taking about fixing, not development. Having said that - the problems you can expect are incomplete fixing, which on film will show up as areas of higher density and color anomalies.

pH is NOT the problem here. In principle a fixer for modern color negative films can be acidic, alkaline or neutral; it doesn't really matter, but generally it's kept close to neutral. Note that a plain solution of sodium thiosulfate and nothing else is pH neutral, so in terms of pH, that would make it close to a color fixer. HOWEVER, the problem is the presence sodium ion that really slows down fixing. There's no way to get rid of that other than not putting it in in the first place. As said, you can add ammonium ion to shift the balance to its favor, which will dramatically speed up fixing; there are recipes for "quasi-rapid" fixers using sodium thiosulfate and e.g. ammonium chloride on this forum and other websites.

 

[thedetective06]

Sorry, so many recipes had it like that and I assumed. Would there be any differences in the capacity of these fixers when used in color?

There are recipes for "quasi-rapid" fixers using sodium thiosulfate and e.g. ammonium chloride on this forum and other websites.

 

[koraks]

Differences between which options?
I'd expect to have the combined sodium thiosulfate + ammonium chloride fixers to have lower capacity than a true ammonium thiosulfate fixer, yes. It'll also likely be a little slower even under optimal conditions. If this is about B&W vs. color film, then assume the capacity for color film will also be lower.

 

[Rudeofus]

Both Fujifilm XF-25 and Ilford Hypam/Rapid fixer are available here, but looking at their data sheets, they both contain acetic acid which will likely mess up the pH.

I did notice someone else was able to adjust the pH of rapid fixer back up to neutral, but I see they added ferric ammonium EDTA here. Do I also need it with a seperate bleach and fix?

You probably refer to this post here, which covers not exactly what you are trying to do. The additional Ammonium Ferric EDTA will turn his soup into a BLIX, which might sound attractive at first, until you realize, that a BLIX has a fraction of the working solution shelf life of a neutral fixer.

If you have a B&W rapid fixer concentrate ready, and chances are that it aims for pH 5.5 (see its data sheet) and not for the desired 6.5, then here is what you can do:

1. Prepare a batch of rapid fixer 1+4 working solution. Maybe add not all the required water at first, since you will add stuff to adjust pH.
2. Add small increments of Ammonia solution to move pH towards neutral. There are two methods to find out, whether your soup is neutral: If it smells a bit like Ammonia, then pH is a bit too high. Add a few dashes of Acetic Acid until the Ammonia smell is gone. If you add a few grains of Sodium Bicarbonate (aka baking soda) to your fixer, and if these grains start to bubble, you pH is still too low, add more Ammonia until further grains of baking soda don't bubble.
3. Record your additions of Ammonia solution and Acetic Acid carefully, next time you know already what you have to add. If you have a pH meter ready, you can forego the smell and the bubble test.

 

[thedetective06]

Is there anyway to test the capacity? I could mix up this for a third of the price of Ilford rapid.

I'd expect to have the combined sodium thiosulfate + ammonium chloride fixers to have lower capacity than a true ammonium thiosulfate fixer, yes.