C-41 RA Bleach Formula Acetic acid substitution

[Nicholas Lindan]

yes, i use vinegar ... anything over 10% is controlled and i will be using 8% for my formulas

It is things like this that make me look forward to shrugging this mortal coil.

 

[kyuut]

Wow! In this case you should seriously look at replenishing instead of using&discarding. This will require some experimentation, but probably save a lot of money down the road.



Wow, I really forgot to put that number 40ml in my formula. it should read:

water 700 ml
PDTA 34g
FeCl3 40% w/w solution 40g
Acetic Acid 80% 40ml
NH4Br 40g

Water ---> 1000ml, pH adjust with NH3 ---> 4.2

@koraks can I ask you to fix that formula in my ancient posting?

returning to this, i was finalizing my shopping list to make your version for the time being. i hadn't realized before that i can't source a NH3 solution.

my research tells me (NH4)HCO3 would decompose into NH3 and CO2 when heated or in contact with the acetic acid, would that be a good substitute while still having a source of NH3?

the only other ammonia option i found would be drug store ammonia at 6% but i'm still trying to find one that doesn't contain other components

 

[lamerko]

Of course, ammonia is actually a gas, so it's perfectly normal that you can't obtain it in that form. What you need is a hydrate - aqueous ammonia at a certain concentration. Here, 25% can be freely purchased from specialized stores, but the most accessible is 10%, which is available in any pharmacy. I'm convinced that 10% should also be available where you are.

 

[kyuut]

Of course, ammonia is actually a gas, so it's perfectly normal that you can't obtain it in that form. What you need is a hydrate - aqueous ammonia at a certain concentration. Here, 25% can be freely purchased from specialized stores, but the most accessible is 10%, which is available in any pharmacy. I'm convinced that 10% should also be available where you are.

Yeah, ammonia solutions are controlled by the police just as 10%+ acetic acid. the highest i could possibly source would be 5,6-6% from the drug store, just need to check if i can find any that is just water and ammonia. if i can't it seems making it from Ammonium bicarbonate would be the better choice

 

[originalwinslow]

@kyuut I am doing something similar. I have been using ferri bleach for a couple years now and have run about 1,000 rolls through that process but am getting tired of the extra time spent washing/toxicity/clearing bath plus the chance for staining. Shipping official chems here is prohibitively expensive due to hazard restrictions. I want to mix my own C-41 bleach but so far cannot source PDTA in the US. Replenishment would be the only way to keep the cost reasonable at scale with these DIY formulas. 50g of ammonium bromide alone is $15, whereas I can mix ferri bleach for under $3/liter.

What I mean to say is...god speed. You've inspired me to start looking into this again.

 

[koraks]

It's a bit offtopic, but in the face of the supply problems faced by both @originalwinslow and @kyuut, would it be feasible to just forget about official C41 bleaches and resort to something like a copper sulfate bleach? I imagine this material might be easier to get hold of, it should be fairly affordable and I expect it can be made into some kind of replenishable or otherwise fairly economical bleach bath. AFAIK it doesn't come with the same fogging problems as ferricyanide bleach, but I might be wrong on this. Correct me if this is the case.

I've not investigated this very deeply; I recall there are one or two threads about (experimental) copper sulfate bleaches for color film here on Photrio. Perhaps it's worthwhile reading up on those.

Again, it strays far from 'official' color processing, but since both have already used ferricyanide bleaches, I suppose sticking to the book is not that much of a requirement anyway.

Edit: here's some good info: https://www.photrio.com/forum/threads/cuso4-bleach-vs-flexicolor-bleach-test-1.68535
Looks like it should/can work (I just did a tiny strip test and I confirm it does seem to work OK) but there are concerns about formation of insoluble copper salts remaining in the emulsion. In part this could be mitigated by a wash step between develop and bleach, but this would of course remove some of the advantage both gents are looking for by moving away from ferricyanide. Whether it can be 'good enough for government work' is a bit of an open question, it seems. It may not be possible to get performance identical to commercial C41 bleaches. But the result may still be good enough, depending on requirements/expectations.

 

[lamerko]

These prices are excessive. In my country, the price of ammonium bromide varies depending on the source, but on average it’s around 30 euros per kilogram - and thats in a glass jar.
On the other hand, things like PDTA, DTPA, and Mercaptotriazole are impossible to find from local suppliers. For that reason, even if I wanted to, I can't make a PDTA bleach. Fortunately, there are ready-made laboratory concentrates available at a good price.
However, there is no import of EDTA bleach for E-6. Thats why I was looking for a way to make one myself. Unfortunately, there is no local source of Ammonium Ferric EDTA, which leaves options 2 and 3 from Rudeofus formulas in the resources section. So far so good - but then came the issue with Mercaptotriazole.
I managed to obtain a small quantity from Germany, but its quality seems somewhat questionable. That's why I was glad about the possibility of substituting it with L-Cysteine. Unfortunately, I had to stop (supposedly for a short time) my work in the darkroom - but its already been… I don't know, nearly two years…

 

[originalwinslow]

It's a bit offtopic, but in the face of the supply problems faced by both @originalwinslow and @kyuut, would it be feasible to just forget about official C41 bleaches and resort to something like a copper sulfate bleach? I imagine this material might be easier to get hold of, it should be fairly affordable and I expect it can be made into some kind of replenishable or otherwise fairly economical bleach bath. AFAIK it doesn't come with the same fogging problems as ferricyanide bleach, but I might be wrong on this. Correct me if this is the case.

This is a creative solution! However, the results shared on that thread (and comments from Ron) were not very convincing. It seems to introduce an equal or greater margin for error compared to ferri bleach with no significant reduction in tertiary steps. Also, greatly extended bleach times are not particularly feasible.

 

[Rudeofus]

Returning briefly to the Ammonium Bicarbonate mentioned by @kyuut : This should actually work very well for you. If you mix the ingredients listed in my formula, you will start somewhere around pH 1. If you add Ammonium Bicarbonate to this acidic soup, it will bubble out the Carbon Dioxide and leave you with the effect of Ammonia. Your pH will go up to 4 or 5 as you add more Ammonia Bicarbonate and bubble out more Carbon Dioxide. The result will be lots of bubbling, which can be annoying, but in the end you'll have the bleach you wanted.

If you mix bleach like this, some Carbon Dioxide will remain in solution, and this will want to get out if you e.g. shake the bottle. Be careful if you shake a tightly closed bottle! Maybe do this a few time: shake the bottle a bit, unscrew the cap to release the pressure, then tighten cap and shake some more.

 

[kyuut]

Returning briefly to the Ammonium Bicarbonate mentioned by @kyuut : This should actually work very well for you. If you mix the ingredients listed in my formula, you will start somewhere around pH 1. If you add Ammonium Bicarbonate to this acidic soup, it will bubble out the Carbon Dioxide and leave you with the effect of Ammonia. Your pH will go up to 4 or 5 as you add more Ammonia Bicarbonate and bubble out more Carbon Dioxide. The result will be lots of bubbling, which can be annoying, but in the end you'll have the bleach you wanted.

If you mix bleach like this, some Carbon Dioxide will remain in solution, and this will want to get out if you e.g. shake the bottle. Be careful if you shake a tightly closed bottle! Maybe do this a few time: shake the bottle a bit, unscrew the cap to release the pressure, then tighten cap and shake some more.

Sounds great! thanks Rudeofus. i’ve read that it would bubble and that making a stock solution of Ammonia bicarbonate would fix that during mixing. i assume it would also make Ph control a little easier with liquid

 

[Rudeofus]

Sounds great! thanks Rudeofus. i’ve read that it would bubble and that making a stock solution of Ammonia bicarbonate would fix that during mixing. i assume it would also make Ph control a little easier with liquid

The bubbling won't change, since it happens if the very acidic bleach preparation gets in touch with Ammonium Bicarbonate. Reaction is something like:

NH4+ + HCO3- + H3O+ <==> NH4+ + 2 * H2O + CO2

The bubbling is good, since it gets the carbonate out, which you wanted gone anyway. On the other side you have to be prepared for it. Use a container at least twice as large as the liquid volume would suggest, add the Ammonium Bicarbonate slowly, so the bubbles don't grow too high and spill over.

 

[kyuut]

The bubbling won't change, since it happens if the very acidic bleach preparation gets in touch with Ammonium Bicarbonate. Reaction is something like:

NH4+ + HCO3- + H3O+ <==> NH4+ + 2 * H2O + CO2

The bubbling is good, since it gets the carbonate out, which you wanted gone anyway. On the other side you have to be prepared for it. Use a container at least twice as large as the liquid volume would suggest, add the Ammonium Bicarbonate slowly, so the bubbles don't grow too high and spill over.

that makes more sense. i will make sure to keep all of that in mind. just gotta decide on which pH meter to buy and source everything. thanks again for all the information!

 

[Achu]

Water (distilled or filtered, 30–35°C) — approx. 600ml

EDTA (Trilon B / Syntron B) 2.5 g

Potassium bromide (KBr) 110 g

Ferric EDTA complex (Iron-EDTA) 130 g

Potassium nitrate (KNO3, crystalline) 30 g

Ammonium acetate (dry powder) 20–25 g

Sulfuric acid (10% solution) add dropwise until pH = 5.7–5.9 (Replaces the glacial acetic acid)

Water to make exactly 1 liter