C-41/ECN-2 Homebrew Stabilizer replacement

drp · Nov 28, 2023

Hello,

As I've just started homebrewing C-41 and ECN-2 development, I was wondering if there are any alternatives to the suggested formula found here for Stabilizer of 10ml of formalin/formaldehyde (+Photo-flo) in 1L of water? While I found I could get formaldehyde without a business license, I was hoping to see if it was possible to avoid using this chemical. I see that other C-41/ECN-2 kits might have hexamine but I haven't been able to find a site that sells it to regular consumers in the U.S. Buying separate stabilizers from the likes of Cinestill or Bellini is not something I'm interested in doing either. I'd prefer making it from scratch or using the raw chemicals if possible. Any ideas?

Thanks!!

koraks · Nov 29, 2023

drp said:
I see that other C-41/ECN-2 kits might have hexamine

I always assumed this to be here as a preservative for the developing agent. BTW, it's present in C41 formulae, but not in official ECN2. Interestingly, it also features in Fuji RA4 developer, at least the CPRA. I can see how it might make sense to add it to ECN2 developer designed for low volume/home use. Anyway, I'm not sure if it somehow functions as a stabilizer for the actual dyes.

Modern C41 film doesn't require a stabilizer, btw, so I wouldn't worry about it.

I guess for your ECN2 film you might do something with a formaline precursor, but it'll still have to convert to formalin during the development process.

Why not just use a little formalin? It's by far the easiest solution and it only takes a tiny bit. While handling large amounts of the stuff in house might not be a good idea, the typical amounts you'd use in a final rinse for color film are so small that I personally wouldn't worry about it.

PS: I trust you've read this: https://www.photrio.com/forum/threads/the-definitive-word-i-hope-on-color-stabilzers.89149

halfaman · Nov 29, 2023

Some biocides widely used for commercial products are isothiazolines (used by Fuji in C-41/CN-16 Superflo Stabilizer) and formaldhyde releasers. Both safe for human handling.

Formaldehyde releaser - Wikipedia

en.wikipedia.org

Isothiazolinone - Wikipedia

en.wikipedia.org

Rudeofus · Nov 29, 2023

koraks said:
I always assumed this to be here as a preservative for the developing agent. BTW, it's present in C41 formulae, but not in official ECN2. Interestingly, it also features in Fuji RA4 developer, at least the CPRA.

This is a lot less mysterious than it sounds: Hexamine hydrolyzes in water and yields Formaldehyde, which we already know as preservative and hardener.

koraks · Nov 29, 2023

My apologies, I was confusing hexamine and hydroxylamine. Fuji CPRA RA4 developer contains a form of hydroxylamine:

No hexamine AFAIK. Sorry for the confusion.

Rudeofus · Nov 29, 2023

koraks said:
My apologies, I was confusing hexamine and hydroxylamine. Fuji CPRA RA4 developer contains a form of hydroxylamine:
View attachment 355040

No hexamine AFAIK. Sorry for the confusion.

That's a modified hydroxylamine. Many standard developers use Hydroxylamine to preserve the color developer, but Hydroxylamine is by itself a developer, which means: if you add too much, you have competition for color developer and therefore lose density. If you use certain substituted hydroxylamines such as this one, you can add more without inducing competitive development.

koraks · Nov 29, 2023

Ah, that's interesting to know. @Photo Engineer once told me that the hydroxylamine present in C41 developer would probably be too weak to be significant. It makes sense to modify it so that it doesn't inhibit at all. It does explain why Fuji's RA4 developer keeps so remarkably well.

drp · Nov 29, 2023

My concern for seeking an alternative was the relatively high toxicity of handling the 37% formaldehyde solution each time I need it. It is my understanding that you shouldn't touch it with bare skin or be smelling it for those reasons. The idea of wearing a mask just to handle this isn't very appealing and if there's one less chemical that I need to do this, the better. Am I going overboard in being overly cautious?

Similarly, handling glacial acetic acid over sulfuric acid is pretty sketchy to me in terms of using either each time for a stop bath for ECN-2. Since I'm using glacial acetic acid, I didn't realize how nasty and stinky that stuff is, especially when using the ferricyanide bleach alternative formula and needing to be extra careful with this approach. I was so used to using a citric acid/water stop bath instead for b&w.

Koraks, And yes, I did read the post by Photo Engineer as linked above. Thanks!

lamerko · Nov 29, 2023

I don't see a drama with sulfuric acid as long as you don't use concentrated. If your source is from the more readily available storage electrolyte (37% sulfuric acid), the dilution is relatively safe as long as the usual precautions are taken. The final solution of the stop bath is about 1% sulfuric acid with an aggressive pH of about 1. I don't know why this is required, but apparently there is a reason. And that's why it might not be a good idea to use acetic acid, which separately smells really bad.
About the formalin - it's a really nasty chemical, although the PE hinted that with reasonable handling it's OK. Realistically, only the E-6 process requires a stabilizer. Obviously you can skip it with ECN-2 and C-41, although it won't hurt and would help against biological pests.

By the way, can I dilute the formalin I have from 37% to about 10% by adding some alcohol in an attempt to stabilize it? Would this reduce hazardous fumes when mixing stabilizer?

koraks · Nov 30, 2023

drp said:
My concern for seeking an alternative was the relatively high toxicity of handling the 37% formaldehyde solution each time I need it.

If this bothers you, dilute it to 5% or 1% and use that. This way you'll only have to handle the stronger solution once in a while and you can do it with gloves on out on the porch/balcony.

drp said:
Similarly, handling glacial acetic acid

Same story. I never handle glacial acetic acid because I find it nasty, so I just buy cans of cleaning vinegar, which is 7-8% acetic acid.

So yeah, I think there are probably easier solutions to your problem than going on a fairly complex chemical hunt.

lamerko said:
I don't know why this is required, but apparently there is a reason.

@Photo Engineer mentioned that this was to rapidly and entirely get rid of any carried-over developer, which he argued was mostly relevant when using a ferricyanide bleach. I've never noticed issues with a much less aggressive acetic acid stop bath in ECN2 processing, however.

lamerko said:
Obviously you can skip it with ECN-2

I don't know, and AFAIK no documentation on this exists. Probably because ECN2 taking film is not made to be archivally stable anyway. I wouldn't be surprised if the dyes are similar to the ones in E6 and they actually do require a stabilizer for archival purposes. Do you have concrete information to the opposite?

Rudeofus · Nov 30, 2023

drp said:
My concern for seeking an alternative was the relatively high toxicity of handling the 37% formaldehyde solution each time I need it. It is my understanding that you shouldn't touch it with bare skin or be smelling it for those reasons. The idea of wearing a mask just to handle this isn't very appealing and if there's one less chemical that I need to do this, the better. Am I going overboard in being overly cautious?

I asked my chems dealer what they would comfortably give me (=amateur doofus), and they gave me 20%. Remember, that Formalin was used to prevent rot in medical specimen, and examiners would routinely handle these with their bare hands while sitting in a closed room which reeked to high heaven. This is the situation in which health effects of Formalin exposure take place, not in photographic amateurs processing color film less than a dozen times per year.

drp said:
Similarly, handling glacial acetic acid over sulfuric acid is pretty sketchy to me in terms of using either each time for a stop bath for ECN-2. Since I'm using glacial acetic acid, I didn't realize how nasty and stinky that stuff is, especially when using the ferricyanide bleach alternative formula and needing to be extra careful with this approach. I was so used to using a citric acid/water stop bath instead for b&w.

Seriously think about using Amidosulfonic Acid or Sodium Bisulfate for making an ECN-2 stop bath. Both come in powder form, which many people consider less concerning than strong acids in liquid form, and both lower the pH close to what Sulfuric Acid does.

If you are concerned about acidic stop bath hurting your Ferricyanide bleach:

A wash step between stop bath and bleach has never hurt
You can buffer the ferricyanide bleach with roughly equal amounts of Sodium Carbonate and Sodium Bicarbonate.

pentaxuser · Nov 30, 2023

koraks said:
Modern C41 film doesn't require a stabilizer, btw, so I wouldn't worry about it.

Any idea why modern sets of C41 chemicals still include stabiliser if it's no longer needed as I thought that modern films started a good many years ago( about 2000) such that almost everyone will have modern C41 film. Is modern stabiliser for C41 in fact Kodak Photo Flo which in turn is the same as Ilford Ilfotol. Neither of which is a stabiliser in any sense of the word

Thanks

pentaxuser

Anon Ymous · Nov 30, 2023

pentaxuser said:
Any idea why modern sets of C41 chemicals still include stabiliser if it's no longer needed as I thought that modern films started a good many years ago( about 2000) such that almost everyone will have modern C41 film. Is modern stabiliser for C41 in fact Kodak Photo Flo which in turn is the same as Ilford Ilfotol. Neither of which is a stabiliser in any sense of the word

Thanks

pentaxuser

It's not stabiliser. It's a wetting agent with some fungicide.

koraks · Nov 30, 2023

pentaxuser said:
Any idea why modern sets of C41 chemicals still include stabiliser

Do they? I think @Anon Ymous is correct:

Anon Ymous said:
It's not stabiliser. It's a wetting agent with some fungicide.

It's often called something like a "final rinse". Heck, even Fuji calls it that for their lab chemistry AFAIK.

Anon Ymous · Nov 30, 2023

koraks said:
Do they? I think @Anon Ymous is correct:

It's often called something like a "final rinse". Heck, even Fuji calls it that for their lab chemistry AFAIK.

Indeed, it's called final rinse.

drp · Nov 30, 2023

Rudeofus said:
Seriously think about using Amidosulfonic Acid or Sodium Bisulfate for making an ECN-2 stop bath. Both come in powder form, which many people consider less concerning than strong acids in liquid form, and both lower the pH close to what Sulfuric Acid does.

If you are concerned about acidic stop bath hurting your Ferricyanide bleach:

A wash step between stop bath and bleach has never hurt

You can buffer the ferricyanide bleach with roughly equal amounts of Sodium Carbonate and Sodium Bicarbonate.

Amidosulfonic acid in powder sounds intriguing. I see that artcraft and ebay carry sulfamic acid, which it seems is the same thing. I have sodium metabisulfate and I can try that one as well. Are there any known issues when using either as a stop bath replacement for ECN-2, such as image quality? How many grams per liter when used in this way? Do either have a lower pH than glacial acetic acid?

I do use a wash step between the stop bath and the ferricyanide bleach steps. Aside from buffering the ferricyanide bleach with sodium carbonate and bicarbonate together, will it affect image quality?

Thanks!

pentaxuser · Nov 30, 2023

Anon Ymous said:
It's not stabiliser. It's a wetting agent with some fungicide.

Thanks Yes I had in the back of my mind that there was something else to stop the "bugs" feeding on the film. Any idea what the fungicide is and if so can this be easily bought and added to the wetting agent?

pentaxuser

Anon Ymous · Nov 30, 2023

pentaxuser said:
Thanks Yes I had in the back of my mind that there was something else to stop the "bugs" feeding on the film. Any idea what the fungicide is and if so can this be easily bought and added to the wetting agent?

pentaxuser

An MSDS probably lists it, but obtaining it might be hard. Buying a ready made product will likely be easier, and buying some formalin even easier. It will work just as well.

koraks · Nov 30, 2023

pentaxuser said:
Any idea what the fungicide is

Anon Ymous said:
n MSDS probably lists it,

Taking that route, for current Fuji C41 final rinse it's this: https://en.wikipedia.org/wiki/Benzisothiazolinone and this: CAS 2682-20-4 https://echa.europa.eu/substance-information/-/substanceinfo/100.018.399

Rudeofus · Nov 30, 2023

drp said:
Amidosulfonic acid in powder sounds intriguing. I see that artcraft and ebay carry sulfamic acid, which it seems is the same thing. I have sodium metabisulfate and I can try that one as well. Are there any known issues when using either as a stop bath replacement for ECN-2, such as image quality? How many grams per liter when used in this way? Do either have a lower pH than glacial acetic acid?

If you look at the pKa values of these compounds: Acetic Acid pKa ~ 4.8, Sulfamic Acid pKa ~ 1, Sulfuric Acid pKa1 ~ -2.8, pKa2 ~2. This means, that in pure diluted form, pH(Sulfuric Acid) < pH(Sulfamic Acid) < pH(Sodium Bisulfite) < pH(Acetic Acid). Both Sulfamic Acid and Sodium Bisulfate are dry powders, which will not boil your water during dilution.

Regarding concentration: I'd try to achieve the same concentration of H3O+, which means you need twice the molar amount of Sulfamic Acid or Sodium Bisulfate than you have Sulfuric Acid in the original stop bath. I doubt that the stop bath is very sensitive to changes in concentration.

drp said:
I do use a wash step between the stop bath and the ferricyanide bleach steps. Aside from buffering the ferricyanide bleach with sodium carbonate and bicarbonate together, will it affect image quality?

I see no reason why it would. If Ferricyanide bleach is specified for ECN-2, then it's exact pH should not matter much.

MattKing · Nov 30, 2023

Anon Ymous said:
An MSDS probably lists it, but obtaining it might be hard. Buying a ready made product will likely be easier, and buying some formalin even easier. It will work just as well.

The chemists will correct me if I am wrong, but my understanding was that formalin isn't their as a bactericide/fungicide, but instead as a stabilizer.
Modern C-41 films don't need it because the stabilizing part of the process comes from something that replaced formalin, and is now found earlier than the final rinse.

Anon Ymous · Dec 1, 2023

MattKing said:
The chemists will correct me if I am wrong, but my understanding was that formalin isn't their as a bactericide/fungicide, but instead as a stabilizer.
Modern C-41 films don't need it because the stabilizing part of the process comes from something that replaced formalin, and is now found earlier than the final rinse.

It's the E6 process where formalin was replaced by a formaldehyde - bisulfite adduct compound in the prebleach bath. AFAIK, in the original E6 process it played a dual role, that of a dye stabiliser and fungicide. I see no reason why it can't be used as a fungicide in a final processing bath.

Rudeofus · Dec 1, 2023

Formalin is an excellent fungicide, since it binds into the gelatin matrix (it's a hardener after all! ) and stays there for decades. Germs hate this trick!

Romanko · Dec 1, 2023

Tetenal C-41 Stabilizer contains Hexamethylenetetramine (hexamine) which is converted to formaldehyde in the solution. The second component is 1,2-benzisothiazol-3(2H)-one, an industrial biocide.

https://tetenal.com/pdf/sds%20en/102221.pdf

Rudeofus said:
Formalin is an excellent fungicide

I believe it was also used as a hardener. Here's my favorite formula: formalin 120 ml; vodka to 1L.

halfaman · Dec 1, 2023

Romanko said:
Here's my favorite formula: formalin 120 ml; vodka to 1L.

Serve cold and garnish with lemon peel...

C-41/ECN-2 Homebrew Stabilizer replacement

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Formaldehyde releaser - Wikipedia

Isothiazolinone - Wikipedia

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