C41 Formulas

[Gerald C Koch]

I would suggest using EDTA instead of the hexametaphosphate. There is the free acid, the disodium salt EDTANa2. and the tetrasodium salt EDTANa4. A combination of two of these would probably get you closer to the desired pH.

 

[Anon Ymous]

EDTA-4na is probably quite close, perhaps less alkaline than DTPA-5Na.

 

[fdonadio]

If you want to follow the bleach formula PE posted to the letter, you need two chelating agents: 1,3-Diaminopropane-N,N,N′,N′-Tetraacetic Acid with CAS # 1939-36-2, and 1,3-Diamino-2-propanol-N,N,N′,N′-Tetraacetic Acid with CAS # 3148-72-9.

@Rudeofus, @Photo Engineer, @mshchem and @Gerald C Koch,

(I think I have tagged almost all the chemists here...)

I finally got a 250g sample of DTPA-Na5 from a chemicals supplier here in Brazil. They will only sell me a minimum order of 25kg, but were so kind to send me (free of charge) two small bottles which will last me some time, I hope.

Still, I can't find those two above — quoted from Rudi's post — except at Sigma-Aldrich (now Merck), which wants an arm and a leg for each.

I searched Photographers' Formulary, Bostick & Sullivan and some Google searches, but came empty-handed. I'm sending an e-mail to Suvatlar right now.

Does anyone know where I can get these? I don't think I can omit the first one, as 30g is not a negligible amount of chemistry. Since I'm a perfectionist, I'd like to follow the formula to the letter, as Rudi said.


Cheers,
Flavio

 

[Rudeofus]

That appears to be the main problem: PDTA doesn't seem to be nearly as widely used as EDTA or DTPA, therefore it's some sort of boutique compound for which one has to pay a hefty price, unless you buy it in ridiculous quantities. Companies who supply minilabs apparently buy ridiculous quantities, and as a result ready to use bleach III is a lot cheaper than just the PDTA we'd need to mix it from scratch. Suvatlar is usually very helpful with hard to get compounds, but he doesn't make these himself, so be prepared to pay more than what you'd have to pay Sigma Aldrich.

On the other side, even if you have to pay 200-250 €/kg of PDTA: you can make at least 30l of bleach, which translates easily into 300-500 rolls of film processed. Their price is easily going to vastly outnumber the cost of PDTA.

 

[Photo Engineer]

Or go back to Ferric Ammonium EDTA.

PE

 

[fdonadio]

Or go back to Ferric Ammonium EDTA.

PE,

The bleach formula call for the three compounds: the 1,3-PDTA, the 1,3-Diamino-2-Propanol-TA and the FeNH4-EDTA!

Judging by the amount of each and your posts on the subject, the last one is crucial. I don’t know the roles of the other two compounds and, for sure, I wouldn’t know what to replace them with.

 

[Photo Engineer]

The last one is crucial. The first two are similar to EDTA. So, I suggest using an equal amount of Ammonium EDTA instead of those first two compounds. Then adjust pH. If you cannot get Ammonium EDTA, then use EDTA and dissolve in a tiny amount of Ammonia.

PE

 

[Rudeofus]

Ammonium Ferric PDTA is significantly stronger than Ammonium Ferric EDTA, so you will need it in higher concentration and with longer bleach times than what the real C-41 bleach offers. Also: I have seen many bleach formulas with Ammonium Ferric EDTA, even some working ones, but never a single one that worked, which didn't use a bleach accelerator, at least not if you wanted complete bleaching within 6 minutes at 38°C/100°F. Replacing the Ammonium Ferric PDTA of the C-41 recipe with Ammonium Ferric EDTA will likely not give you a working bleach.

If you want to bleach any C-41 or E-6 product with Ammonium Ferric EDTA bleach, you need to use a prebleach with a good bleach accelerator . Fuji's recipe has a prebleach and bleach recipe for E6, which also works for C-41, Substitute the Thioglycerol (ubobtainium for us amateurs, and it smells, so no harm done) in prebleach with roughly equal amount of Mercaptotriazole (which is odorless, works and is available from Photo Formulary, Fototechnik Suvatlar and maybe some others), use Formalin and Sodium Bisulfite instead of Formalin Bisulfite adduct, leave out the Ammonium Nitrate from bleach formula and be done with it. Lower bleach pH to 5.0, if its action is too weak/slow.

 

[Anon Ymous]

If the price of a bleach ingredient turns out to be ridiculously high, or the ingredient itself is unobtainium, then one may as well accept defeat and go buy some ready made bleach. Minimum quantity will probably be a lot, but it won't spoil, so you can think of it as an investment.

 

[fdonadio]

Replacing the Ammonium Ferric PDTA of the C-41 recipe with Ammonium Ferric EDTA will likely not give you a working bleach.

I’m confused. The recipe in the OP calls for Ammonium Ferric EDTA, not PDTA.

If the price of a bleach ingredient turns out to be ridiculously high, or the ingredient itself is unobtainium, then one may as well accept defeat and go buy some ready made bleach. Minimum quantity will probably be a lot, but it won't spoil, so you can think of it as an investment.

You’re right. I think I should talk to a lab owner and buy some bleach. Since I already have all the other raw chemicals, I’ll mix all the other stuff from PE’s recipe.

Buying from Kodak or Fuji (or their distributors) involves minimum quantities which are way over my budget at the moment.

 

[Rudeofus]

I’m confused. The recipe in the OP calls for Ammonium Ferric EDTA, not PDTA.

The recipe asks for Ammonium Ferric EDTA, Ammonia, Ferric Nitrate and PDTA, that latter two added in a molar ratio of about 1 : 1.1. Guess what you get ...

 

[Photo Engineer]

Or, as I wrote, you can go with all EDTA making Ammonium Ferric EDTA. But, you need more EDTA than Iron salt and you need to adjust pH. This is very complex (pun intended) chemistry. I do suggest that you send your film out or buy a prepared mix.

Also, use longer process times than suggested, if you mix your own or use an EDTA based bleach (or blix) as they are weaker than those containing PDTA.

PE

 

[Rudeofus]

PS: In case the extra compound "1,3-diamino-2-propanol tetraacetic acid" raises questions: this is not directly for bleaching, but seems to act as very effective water hardness sequestrant, see this patent for a brief description. There's a good chance that you won't need it in your bleach, and if you did: mixing your bleach with deionized water would be orders of magnitude cheaper than the outrageous prices Sigma Aldrich asks for this compound.

 

[fdonadio]

The recipe asks for Ammonium Ferric EDTA, Ammonia, Ferric Nitrate and PDTA, that latter two added in a molar ratio of about 1 : 1.1. Guess what you get ...

I stand corrected. I should have paid more attention to the organic chemistry classes.

PS: In case the extra compound "1,3-diamino-2-propanol tetraacetic acid" raises questions: this is not directly for bleaching, but seems to act as very effective water hardness sequestrant

I have a deionizing filter, but I use it for wash water. I mix all my chemistry with distilled water — dirt cheap when bought in 25-liter drums.

I’m gonna try to find DTPA one last time.

 

[fdonadio]

This is very complex (pun intended) chemistry.

I laughed.

Now, a little more seriously, if you say this is complex, it might be too complex for me.

 

[Photo Engineer]

It took me days to work this out. I have several formulas and a patent on this.

PE

 

[fdonadio]

It took me days to work this out. I have several formulas and a patent on this.

PE

Yes, I know. It was just me trying to be funny.

It sure is ultra-complex for me, as I didn’t go to college to study chemistry. I started a course in that we call something like “professionalizing high-school”, in Industrial Chemistry, but didn’t finish it.

It was around 25 years ago. Even if I had finished the course, if I didn’t get a job on the area and went to college, I would never have the knowledge to understand the color development process as deeply as you do.

 

[Photo Engineer]

That is why I always suggest getting premixed stuff rather than doing it yourself.

PE

 

[fdonadio]

That is why I always suggest getting premixed stuff rather than doing it yourself.

PE

Wait! Weighing and mixing stuff in water is easy enough. I surely can do that, as I did harder stuff in the school lab. For example, in analytic chemistry, I have hands-on experience in separating groups A and B cations in the lab (OK, my experience stops right there ).

I also learned lab best practices, like organization, cleaning and safety — the first two days in the lab were entirely dedicated to safety and I take it as seriously now as I did back then.

Now, the multi-decade experience in film development processes you have is rather hard to acquire, to say the least.

Don’t get me wrong, but I don’t think I need to know all that to follow a “recipe”. Now, if I need to change that “recipe”, then I sure need help from you and other acknowledged member of Photrio. I am not afraid or embarrassed to ask for that.

I mix my own D-76 and Dektol all the time, since Kodak doesn’t sell them anymore in Brazil. But that way too easy.

 

[Photo Engineer]

Well, the proper chemicals are hard to get, so you are scratch mixing and want to "change" the formula, and this is typical of scratch mixing color. So, you are looking for substitutes, and hoping to get it right. When I got a bleach formula wrong (or blix), I was left with either stain or remaining silver. Those are at the top of my list of problems I used to see. When I got it right, the thing worked, and Kodak is still selling it for RA4. They never did use the blix or bleach for film, but have gradually moved the C41 fix in the direction of one we designed many years ago.

When we started, you could not buy Ammonium Ferric EDTA. Thanks to Stephen and Surash, they designed a method to make it at high temperature and pressure.

I wish you good luck and will help here as long as possible, assisting you no matter what you decide to do.

PE

 

[fdonadio]

Well, the proper chemicals are hard to get, so you are scratch mixing and want to "change" the formula, and this is typical of scratch mixing color. So, you are looking for substitutes, and hoping to get it right.

I see what you mean and that's why I asked if and how I could change the formula. Maybe the answer is "no, you shouldn't change the formula". I could live with that.

In that case, I can just find a way to buy Kodak or Fuji readymade bleach and be done with it. The sole Kodak-Alaris' distributor in São Paulo has a minimum order of US$ 600. If only they had 120 film and HC-110, I could find some friends to split an order. But Kodak-Alaris Brasil doesn't work with medium or large format film anymore — only 135 and, incredibly, Duratrans —, and also dropped B&W chemistry from their list, even the powdered ones. Go figure.

I wish you good luck and will help here as long as possible, assisting you no matter what you decide to do.

I thank for you very much for the time you spend here every day answering to my [sometimes very, sometimes just a little stupid ] questions and from other members. It's been really nice of you, seriously.

-Flavio

 

[Photo Engineer]

I'm so sorry about that.

Here is a suggested starting point....

Water 600 ml
Sodium Ferric EDTA 90 g
Sodium Sulfite 10 g
Tetra Sodium EDTA or better still Tetra Ammonium EDTA 10 g

Water to 1L ... pH 6.0 - 6.5

It will take 10 or more minutes to bleach. You may have to add some Ammonium Bromide. I have not tested this.

This is a simple home-made bleach. If you want a blix, use the formula in the patent.

PE

 

[fdonadio]

I had the most pleasant surprise some minutes ago.

The company that gave me the DTPA-Na5 sample also sells 1,3-PDTA – and some other stuff, including Fe-NH4-PDTA! I was at the right place, but didn't notice it.

I have just contacted them. Who knows how crazy they are about giving out samples. I didn't ask for that, specifically, but...

 

[carlos graca]

You are correct. Kodak Bleach III is about 5.5 though, and I know that pH 4.5 bleaches are possible. I have formulated them myself. Don't try to make a blix at that pH though! Oh, and remember that the dyes do not necessarily like wide pH swings.

PE

Hi Ron, yesterday I did try some ecn-2 film processing with ra-4 chemicals but the film come out a bit dark. It looks like the Dev did a prefect job, lots of detail, but the Fix not,,, it was a bit dark with a blue cast. What do you think, should I strength the Fix (I use 1+9) or increase the time of fixing? Or something else?
Thanks so much, Carlos

 

[Photo Engineer]

It is a matter of bleaching and fixing. You must redo both. RA4 chemistry is not strong enough for C41 films.

PE