Mixing Ammonium Thiosulfate for use in ECN2 process

[kizu]

Hello,
I am trying to mix chemicals for ECN2 process. For the Fixer it is quite hard to get C41 Fixer as substitute so I want to mix it myself.
I can not find Ammonium Thiosulfate but I read that it is possible to mix it out of Sodium Thiosulfate and Ammonium Chloride.

I often came across the numbers 200g of Sodium Thiosulfate and around 50-80g of Ammonium Chloride.
So for mixing the final Fixer solution can I mix in order to make 1 Liter:

200g of Sodium Thiosulfate
80g of Ammonium Chloride
10g of Sodium Sulfite
8.4g of Sodium Metabisulfite

The last two chemicals are the other chemicals prescribed by kodak ecn-2 formulas to get the fixer.

 

[koraks]

mix it out of Sodium Thiosulfate and Ammonium Chloride

Don't bother and just use any B&W rapid fixer. An acidic fixer (which most B&W fixers are) is perhaps not officially intended for a color process, but it will work nonetheless.

 

[lamerko]

Hello,
Ammonium thiosulphate can be obtained from Mr. Suvatlar - he sells it in 1 and 5 liter tubes, at a good price. The official formula is simple and mixes in literally 2-3 minutes.

 

[koraks]

he sells it in 1 and 5 liter tubes

Yeah, 60% solution. It's surprisingly difficult to obtain for private consumers despite being a fairly common substance. Suvatlar's offer is very reasonable in this light.

 

[lamerko]

Yeah, 60% solution. It's surprisingly difficult to obtain for private consumers despite being a fairly common substance. Suvatlar's offer is very reasonable in this light.

Yes, I bought a 5 liter tube and I am very satisfied.

 

[koraks]

That'll fix a lot of stuff.

 

[Pelovsky]

An acidic fixer (which most B&W fixers are) is perhaps not officially intended for a color process, but it will work nonetheless.

I wouldn't be so sure about it. At least in ORWO's color processes you weren't supposed to use acidic fixer, beacuse it affected the dyes.
I'd thought that C41 fixer - e.g. Fujihunt Negacolor Fixer - is widely available and cheap (it is in Poland, 50 euros for 4x10l concentrate).

 

[koraks]

At least in ORWO's color processes you weren't supposed to use acidic fixer, beacuse it affected the dyes.

The ORWO films you refer to involve dye technology that was departed from by Western manufacturers many decades ago. Indeed, it's possible these dyes can remain in leuco state if the last concentrated processing bath is acidic. Note that OP refers to ECN2, which implies films like Vision3 or perhaps old Vision2 and Eterna, none of which will be particularly prone to the leuco dye problem.

I'd thought that C41 fixer - e.g. Fujihunt Negacolor Fixer - is widely available and cheap (it is in Poland, 50 euros for 4x10l concentrate).

It is in Europe. OP's local situation may be different.

 

[Don_ih]

it is possible to mix it out of Sodium Thiosulfate and Ammonium Chloride.

I made rapid fixer that way two times. Both times, within a week or so, it sulfured-out. That's when you get a yellowish sludge sitting in the bottom of the container and the fixer is then dead. I didn't bother to try to figure out why it did that so quickly (it was at room temperature the whole time) - I just never bothered doing it again.

I also used to buy ammonium thiosulfate in solution and make alkaline fixer. It's cheaper to buy alkaline fixer premade.

 

[koraks]

I made rapid fixer that way two times. Both times, within a week or so, it sulfured-out.

Did you add any sulfite?
I made a small batch (500ml) ten days ago or so; haven't used it, yet, but it still looks fine and it's perfectly clear, still.
The main qualms I have with this approach, are:
* Sodium thiosulfate pentahydrate has a pretty low solubility limit. Allegedly, it's around 70g/100ml at 20C (you'll need to warm the solution since the solution cools down rapidly as the thiosulfate dissolves), but I never managed to dissolve nearly that much.
* The significant amount of ammonium chloride, even though it's an ammonium salt (so readily soluble), doesn't help with the solubility limit of the thiosulfate
* The net result is you basically cannot make a concentrated fixer and you're stuck with working strength or maybe a quasi-concentrate that dilutes 1+1 or thereabouts - so it ends up taking quite a lot of space if you premix ahead of use.
* Ammonium chloride is really only attractively cheap if bought in large quantities, at least last time I checked. So you end up with big containers of stuff and spend a lot of time weighing, hacking at big clumps of caked thiosulfate, stirring, maybe some filtering....

Overall, it's a lot of work to substitute a perfectly usable ready-made product (i.e. rapid fixer) that's available cheaply almost anywhere on the planet.
Fixer is one of those things that in my mind makes very little sense to try and make yourself. I've done it many, many times - but really only to get rid of the various batches of thiosulfate I somehow ended up with over the years.

 

[Don_ih]

Did you add any sulfite?

I followed a formula, so I put in whatever it said. I just don't recall what formula. It was about 6 or 7 years ago.

 

[koraks]

OK, well, most formulas for sod.thiosulfate + ammonium chloride I've seen do include sulfite, and it's indeed necessary to protect the thiosulfate from oxidizing. Not sure why yours sulfured out. I do note, however, that most thiosulfate I've used (esp. ammonium, sodium to a far lesser extent) contains a small 'residue' of solid sulfur that makes the solution cloudy, initially. This will sink to the bottom if it's not filtered out after mixing. But in this case, it's immediately visible after mixing in the form of a distinct cloudiness; if you didn't see that, then for some reason yours did indeed sulfur out surprisingly quickly.

 

[lamerko]

I really don't see any point, given that there is a source of ammonium thiosulphate.
And yes, sodium thiosulfate only goes bad in days when the pH rises above some limit. From personal experience...

 

[koraks]

given that there is a source of ammonium thiosulphate.

For you, yes. Local conditions vary. OP's situation may be very different.

 

[lamerko]

If I'm not mistaken, according to his signature, he's in Germany?

 

[koraks]

If I'm not mistaken, according to his signature, he's in Germany?

Not necessarily; many places can be identified with "DE". In this case, I'm pretty sure it's not Germany, although I initially thought so, too.

 

[Pelovsky]

Note that OP refers to ECN2, which implies films like Vision3 or perhaps old Vision2 and Eterna, none of which will be particularly prone to the leuco dye problem.

According to Kodak's ECN-2 process specification (H.24.7) page 7-33: "the fixer pH should never be allowed to fall below 5.5, since low fixer pH affects the dye stability of Kodak color negative films."

 

[Don_ih]

yours did indeed sulfur out surprisingly quickly

It did indeed. And it worked very well up to that point. So I have no idea what the problem was. I assumed it was a mistake on my part. When it happened the next time, I assumed it was a mistake in whatever formula I followed. Then I gave up and started ordering big jugs of rapid fix.