Making and Maintaining Bleaches for E-6 Process

Rudeofus · May 23, 2023

Rudeofus submitted a new resource:

Making and Maintaining Bleaches for E-6 Process - Formulas and procedures for making and maintaining E-6 bleaches from raw ingredients

1.) if you have a bottle of Ammonium Ferric EDTA (typically comes as 43-50% w/w solution):

Prepare 700ml water

Add 100ml of this Ammonium Ferric EDTA solution

Add 50-100 g Ammonium Bromide

Add Acetic Acid to bring pH somewhere between 4 and 5.

When pH is where you want it, top up with water to make 1000ml.

2.) If you have EDTA free acid, you can start with:

600ml water

108g EDTA free acid

80g Ammonium Bromide

140g...

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Anon Ymous · May 23, 2023

In case you have the free acid, you can also use ferric nitrate (usually nonahydrate) instead of the chloride. Your formula has a slight excess of free acid and about 140g of ferric nitrate nonahydrate sound about right instead of the 140g of ferric chloride solution.

Rudeofus · May 23, 2023

Anon Ymous said:
In case you have the free acid, you can also use ferric nitrate (usually nonahydrate) instead of the chloride. Your formula has a slight excess of free acid and about 140g of ferric nitrate nonahydrate sound about right instead of the 140g of ferric chloride solution.

Yes, it was quite surprising to me to see, that one could replace Fe(NO3)3 * 9 H2O powder gram for gram with Ferric Chloride 40% w/w solution, but the numbers do add up quite accurately.

There is a slight excess of EDTA compared to Ferric content, that's quite intentional. One of Ron's patents specifies that EDTA excess to be somewhere around 1%, and Ron was quite adamant about that this was really important to make bleaches work well.

lamerko · Jun 5, 2023

Ferric nitrate can be harder to find in some regions and is quite a bit more expensive. Ferric chloride, on the other hand, is cheap, but in large cuts - about $35 for 20 liters of a 40% solution.
Can this bleach be modified for C-41? I guess the bromide can be reduced…

Rudeofus · Jun 6, 2023

In a way, bleaching of C-41 is a tad easier than E-6, since less silver has to be bleached back. However, I recommend you use the same amount of NH4Br, since with Ammonium Ferric EDTA there has to be an overabundance of bromide to shift the balance in the right direction.

The other thing different for C-41 is the fact, that C-41 materials withstand stronger bleaches than E-6 or RA-4. Therefore we can make C-41 bleaches with Ammonium Ferric PDTA. This is a compound quite similar to Ammonium Ferric EDTA, but the PDTA forms a weaker complex with ferric ion than EDTA, and as a result Ammonium Ferric EDTA is a stronger oxidizer. This allows more dilute bleaches and also a bromide amount which more closely resembles the bromide amount needed for the actual bleaching reaction. I may post some formulas later if there is any interest.

lamerko · Jun 12, 2023

Rudeofus said:
I may post some formulas later if there is any interest.

Yes, that would be nice

Rudeofus · Jul 5, 2023

lamerko said:
Yes, that would be nice

Shame on me, I forgot my own posting from a year ago, in which I already shared my C-41 bleach formulas.

fert · Oct 3, 2023

亲爱的Rudeofus，根据上面的例子，我不知道是否可以制作浓缩物，以便于储存和使用。
(Dear Rudeofus, Based on the example above, I wonder if it is possible to make a concentrate so that it can be stored and used easily.)

Rudeofus · Oct 3, 2023

fert said:
亲爱的Rudeofus，根据上面的例子，我不知道是否可以制作浓缩物，以便于储存和使用。
(Dear Rudeofus, Based on the example above, I wonder if it is possible to make a concentrate so that it can be stored and used easily.)

Ammonium Bromide is very soluble, you should easily dissolve 50g Ammonium Bromide in 80ml water and then add the Acetic Acid. Make one batch of working solution, record the amount of Acetic Acid need to reach pH 4.5, then do the following:

Prepare 80ml water
Add 50 g Ammonium Bromide
Add the measured amount of Acetic Acid
Add 100ml of this Ammonium Ferric EDTA solution
Add some water to make a round number (like 200ml, 250ml, 333ml), so that mixing smaller batches becomes easy

The only advantage of this concentrate is the lower space requirement, you will not improve its shelf life (which is already more than a year with regular working solution).

fert · Oct 3, 2023

Rudeofus said:
溴化铵极易溶解，您应该轻松地将 50 克溴化铵溶解在 80 毫升水中，然后加入乙酸。配制一批工作溶液，记录达到 pH 4.5 所需的乙酸量，然后执行以下操作：

准备80毫升水

添加 50 克溴化铵

添加测得的乙酸量

添加 100ml EDTA 铁铵溶液

添加一些水以形成整数（例如200ml、250ml、333ml），以便混合小批量变得容易

这种浓缩物的唯一优点是空间要求较低，不会延长其保质期（常规工作溶液的保质期已经超过一年）。

fert · Oct 3, 2023

Dear rudeofus, thank you very much for your answer. I don’t know about Will there be any posts about the fixing part and final rinse behind Kodak US5948604A, or are there any better recommendations?

koraks · Oct 3, 2023

fert said:
final rinse

In case you hadn't seen it yet, I'd recommend giving this a read: https://www.photrio.com/forum/threads/the-definitive-word-i-hope-on-color-stabilzers.89149/unread
It may already answer your question on this part.

fert · Oct 3, 2023

Thank you so much

Rudeofus · Oct 3, 2023

fert said:
Dear rudeofus, thank you very much for your answer. I don’t know about Will there be any posts about the fixing part and final rinse behind Kodak US5948604A, or are there any better recommendations?

Regarding fixer: Kodak's formula is a very peculiar construct, since it's used single shot. We don't usually want to do this, therefore we will rather use a more concentrated working solution. I therefore recommend either Ryuji Suzuki's Neutral Rapid Fixer formula, or Ron Mowrey's Superfix 1 formula.

Regarding Final Rinse: commercially available final rinse for E-6 and C-41 contains a powerful biocide, which is extremely toxic to humans in its pure forms. Being amateurs we will not be able to buy this compound. Therefore korak's suggestion is our only option.

lamerko · Oct 17, 2023

Hello again,
finally, I began to procure the necessary chemicals for the second formula with the free EDTA acid. Accordingly, I need the ingredients for the pre-bath, but it looks like Mercaptotriazole will still be a problem. I looked again at Axelcolor's Ebay store, but apparently I was wrong last time - they sell something else, MERCAPTOPHENYLTETRAZOLE CAS 86-93-1, which is a powder. I will try to order a small amount of 1-Thioglycerol CAS 96-27-5 (Liquid) from Alibaba, but I may not succeed. Anyone know of a source for this in Europe?

Anon Ymous · Oct 17, 2023

lamerko said:
I looked again at Axelcolor's Ebay store, but apparently I was wrong last time - they sell something else, MERCAPTOPHENYLTETRAZOLE CAS 86-93-1, which is a powder.

They don't list it, but they have mercaptotriazole, or at least they did some years ago. Ask them. Oh and mercaptotriazole is also a powder.

Rudeofus · Oct 18, 2023

lamerko said:
Hello again,
finally, I began to procure the necessary chemicals for the second formula with the free EDTA acid. Accordingly, I need the ingredients for the pre-bath, but it looks like Mercaptotriazole will still be a problem. I looked again at Axelcolor's Ebay store, but apparently I was wrong last time - they sell something else, MERCAPTOPHENYLTETRAZOLE CAS 86-93-1, which is a powder. I will try to order a small amount of 1-Thioglycerol CAS 96-27-5 (Liquid) from Alibaba, but I may not succeed. Anyone know of a source for this in Europe?

You can buy Mercaptotriazole from Fototechnik Suvatlar, ask Saban if they don't list it. While Thioglycerol and Thioglycolic Acid also work and are certainly cheaper than Mercaptotriazole, but they may be difficult to buy for amateurs. For strange reasons it was easier to obtain Thioglycolic Acid Sodium Salt, because "Thioglycolic Acid is an acid, we can't ship that to you, but the sodium salt is fine". WTF.

Once I am through with my bottle of Thioglycolic Acid Sodium Salt there will be a switch to Mercaptotriazole, because I really hate the smell of the former.

lamerko · Oct 18, 2023

Rudeofus said:
You can buy Mercaptotriazole from Fototechnik Suvatlar, ask Saban if they don't list it. While Thioglycerol and Thioglycolic Acid also work and are certainly cheaper than Mercaptotriazole, but they may be difficult to buy for amateurs. For strange reasons it was easier to obtain Thioglycolic Acid Sodium Salt, because "Thioglycolic Acid is an acid, we can't ship that to you, but the sodium salt is fine". WTF.

Once I am through with my bottle of Thioglycolic Acid Sodium Salt there will be a switch to Mercaptotriazole, because I really hate the smell of the former.

Thanks. I put in an inquiry - I hope they have it so that I don't deal with Alibaba. I'm getting some weird offers - $17 value and over $150 shipping, seperate and some fees...

Josaw98 · Mar 31, 2024

Rudeofus said:
Rudeofus submitted a new resource:

Making and Maintaining Bleaches for E-6 Process - Formulas and procedures for making and maintaining E-6 bleaches from raw ingredients

Read more about this resource...

Hello @Rudeofus thank you very much for sharing your knowledge, I have been developing my own E6 for some years, I have used C41 DTPA bleach, but the loss of saturation is visible, they are not bad but they could be much better, I am going to do the Bleach as you mention in this thread . I just have a few questions:

In this patent Fuji (US6720134B2) uses potassium bromide and ammonium nitrate in the bleach, in its case it uses ammonium bromide directly, is there any difference in terms of result?

In the aforementioned patent it uses 0.4g/l of 1-thioglycerol, in my case it is easy to get thioglycolic acid (80-90%), can I replace it in the pre-bleach with the same molar? It is a large amount and should I use 0.1g/L as mentioned?

I use l-cysteine as an antioxidant agent for the CD and a yellow spot does not form in the highlights. I see that thioglycolic acid contains a thiol like L-cysteine. Is it still necessary to use L-cysteine?

I appreciate you reading me

Rudeofus · Mar 31, 2024

The question KBr vs. NH4Br in bleach is a question of cost, availability and how long your washing cycle will be after bleach. In many cases KBr will be much cheaper, and it will likely work just as well. The biggest issue with potassium ions is if you get them into your bleach in larger amounts, they form an insoluble mixed salt with silver, thiosulfate and bromide, which greatly diminishes the capacity of your fixer. If you look at the Kodak 5l kit patent: they go directly from bleach to fixer in order to speed up processing time, so Kodak's patent had to use the precursors to NH4Br. Fuji's patent as far as I remember has a wash step between bleach and fixer and can therefore use the cheaper KBr.

Regarding the nitrate in bleach: many professional outfits process in stainless steel tanks, which are allegedly corroded by bleach. The nitrate somehow prevents this, I don't know why and was never offered an explanation. If you process in plastic tanks, you should skip the nitrate and thereby also avoid gov't questioning "what exactly do you plan to use nitrate for???".

Regarding 1-Thioglycerol: it's a bleach accelerator, which reeks to high heaven, like many of its replacement options like 1-Thioglycolic Acid and its salts. In general it's a bit easier to get 1-Thioglycolic Acid Sodium Salt, because "it's not an acid so we would ship it to you". A somewhat different, but according to a patent preferable option is Mercaptotriazol. This one is mostly odorless and works just as well. AFAIK Tetenal used in in their BLIX for the same purpose.

Regarding amount: The amount is somewhat difficult to adjust, since it sticks to silver, so it gets removed during processing. Adding too much actually kills the bleach, so you are wedged between a rock and a hard place. Therefore professional E-6 process designers performed a smart move: they put the bleach accelerator into the prebleach and designed the process to go from prebleach directly into bleach. This sort of replenishes the bleach accelerator level in the bleach even if you reuse, and at the same time its level stays low enough to keep the bleach active.

Mercaptotriazole should be available from Suvatlar in Germany, and since you are on the American continent, you could check with Formulary or Artcraft. If you insist on thioglycolic something and have a source for it, then please put it in the prebleach and use simple molar substitution.

Finally regarding the Cysteine: I've seen many patents for bleach accelerators, which mention a large range of viable compounds, and I don't remember Cysteine mentioned in any of these. These patents also don't mention a reaction mechanism behind this bleach acceleration, so I have no idea upfront, which compound works and which doesn't. I am not even sure, whether the patenting entities knew, why their soups worked. Conclusion: it's unlikely that Cysteine works as bleach accelerator, but you can always try, since bleaching runs to completion, can happen in room light and can be repeated as often as needed.

Josaw98 · Mar 31, 2024

Excellent, I will not make it more complicated and I will follow the formula you propose regarding ammonium bromide.

As for the Bleach accelerator, I understand that the ideal would be to use Mercaptotrizole, however here in Mexico it is difficult to obtain, like 1-thioglycerol, thioglycolic acid costs $30 per 125ml and is easy to obtain. I hope to get Mercaptotrizole in the future.

I saw in a Kodak patent (right now I don't have anything to leave a reference) use L-cysteine as an antioxidant agent for the CD to prevent the latter from oxidizing in contact with bleach. It didn't say anything about an accelerator and I'm almost sure it wouldn't work like that. I will do a test with and without L-cysteine in the pre-bleach to see if yellow spots are generated in the highlights.

Rudeofus · Apr 1, 2024

alons98 said:
As for the Bleach accelerator, I understand that the ideal would be to use Mercaptotrizole, however here in Mexico it is difficult to obtain, like 1-thioglycerol, thioglycolic acid costs $30 per 125ml and is easy to obtain. I hope to get Mercaptotrizole in the future.

The biggest advantage of Mercaptotriazole is that it's virtually odorless, which is quite an improvement once you have smelled these thioglycerols even as dry powder. The plastic bottle I received with Thioglycolic Acid Sodium Salt even carries a sticker "store at -20°C". I never did that, but it does smell a bit like it in my chem closet. I will celebrate the day, when it's all gone :-D

lamerko · Apr 1, 2024

If no accelerator is applied, how long will it take to bleach?

Rudeofus · Apr 1, 2024

lamerko said:
If no accelerator is applied, how long will it take to bleach?

You'd have to try and measure with an IR capable scanner. I'd also worry, that prolonged immersion of E-6 film in a weak oxidizer may be still out of spec for archival stability of the slides, sort of same as 6 minute long immersion in too strong bleach.

Josaw98 · Apr 2, 2024

Rudeofus said:
The biggest advantage of Mercaptotriazole is that it's virtually odorless, which is quite an improvement once you have smelled these thioglycerols even as dry powder. The plastic bottle I received with Thioglycolic Acid Sodium Salt even carries a sticker "store at -20°C". I never did that, but it does smell a bit like it in my chem closet. I will celebrate the day, when it's all gone :-D

I hope you can finish that smell soon, while I'll just start haha!

Well today I started preparing the bleach while I wait for the thioglycolic acid and the ammonium bromide to arrive, however I made a beginner's mistake and did not read your instructions, I added the ferric chloride before the ammonium bromide, what happened then? The EDTA precipitated, I added ammonia again little by little and the precipitate disappeared. I have a dense red solution. My question is, will it still work or should I start again from scratch?

Making and Maintaining Bleaches for E-6 Process

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