C41 PDTA Bleach Recipe

yoso20 · Jun 1, 2022

Hey there!
I saw a lot of posts from Ron (photo engineer) and other users about bleach recipe, but all of them are mostly ferricyanide based, or using the EDTA. I know the newest kodak flexicolor bleach III uses PDTA instead, does anyone have the figures for that by any chance?

Thanks!

koraks · Jun 1, 2022

Google turns up this one (post #2): https://www.photrio.com/forum/threads/c41-formulas.142062/

I guess that's as good as it gets in terms of online published formulas.

Murray Kelly · Jun 2, 2022

In the BJP Annual 1975 the formula for Kodacolor II bleach is

Sequestrene Na Fe ...... 100g
KBr ......50g
Ammonia 20% 6ml
Water to 1L
pH 5.9 - 6.1 4m20sec @38C +-3C

I use strong household ammonia (cloudy) and the Manutec iron chelate is the cheap EDTA sodium salt at USD10 for 300g.
I added NH4Cl to the KBr and I think it is faster and amm. Br could well eliminate both ammonia and KBr. I give it longer.

Rudeofus · Jun 5, 2022

@koraks: while this formula does indeed contain a trace amount of PDTA, its bulk bleach component is Ammonium Ferric EDTA. Likewise the formula posted by @Murray Kelly is based on Sodium Ferric EDTA, which is even slower.

There are 3 recipes I can add to this discussion, which are based on Ammonium Ferric PDTA:

1.) Kodak Bleach III for C-41 RA process. This is a very concentrated and fast acting version (RA means rapid action) and was published in the patent US6649331:

PDTA 113.6g
2,4-Dihydroxybenzophenon 0.95g
Acetic Acid 80% 64.4 ml
NH4Br 94.67 g
Fe(NO3)3 * 9 H2O 136.93

water ---> 1000ml, use NH3 solution to bring pH up to 4.5.

2.) PDTA bleach based on Konica patent US6225018:

water 700ml
Ammonium Ferric PDTA 125g
EDTA 2.0g
NaNO3 40g
NH4Br 150g
Glacial Acetic Acid 40g

water ---> 1000ml, pH ----> 4.4

3.) My personal Ammonium Ferric PDTA based bleach. It is a lot less concentrated than the Kodak and the Konica formula, and it avoids freak ingredients:

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

Add NH3 solution to bring pH to 4.2, then add water to make 1000ml. If you have access to Fe(NO3)3 * 9 H2O, you can replace the Ferric Chloride 40% w/w solution 1:1, i.e. with the exact same weight. The nitrate used in the patented bleaches is there to protect stainless steel tanks. Since we mostly use plastic tanks, we can safely skip this ingredients and have one less worry, when cops show up in our dark room.

If you can't obtain Acetic Acid 80% in your country, use whatever concentration you can buy and do the math.

All three formulas will be mixed as follows:

mix all components in given order
the solution will be very acidic and a white PDTA precipitate will appear
Slowly add NH3 solution. pH will shoot up initially, but will go down to ~1 again until all the PDTA is dissolved
Keep adding NH3 until all the PDTA is dissolved and until target pH is reached
Do not overshoot NH3, because if that soup ever becomes alkaline, it will precipitate Ferric Hydroxide, which is difficult to dissolve again.

minh0204 · Jun 6, 2022

Rudeofus said:
@koraks: while this formula does indeed contain a trace amount of PDTA, its bulk bleach component is Ammonium Ferric EDTA. Likewise the formula posted by @Murray Kelly is based on Sodium Ferric EDTA, which is even slower.

There are 3 recipes I can add to this discussion, which are based on Ammonium Ferric PDTA:

1.) Kodak Bleach III for C-41 RA process. This is a very concentrated and fast acting version (RA means rapid action) and was published in the patent US6649331:

PDTA 113.6g
2,4-Dihydroxybenzophenon 0.95g
Acetic Acid 80% 64.4 ml
NH4Br 94.67 g
Fe(NO3)3 * 9 H2O 136.93

water ---> 1000ml, use NH3 solution to bring pH up to 4.5.

2.) PDTA bleach based on Konica patent US6225018:

water 700ml
Ammonium Ferric PDTA 125g
EDTA 2.0g
NaNO3 40g
NH4Br 150g
Glacial Acetic Acid 40g

water ---> 1000ml, pH ----> 4.4

3.) My personal Ammonium Ferric PDTA based bleach. It is a lot less concentrated than the Kodak and the Konica formula, and it avoids freak ingredients:

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

Add NH3 solution to bring pH to 4.2, then add water to make 1000ml. If you have access to Fe(NO3)3 * 9 H2O, you can replace the Ferric Chloride 40% w/w solution 1:1, i.e. with the exact same weight. The nitrate used in the patented bleaches is there to protect stainless steel tanks. Since we mostly use plastic tanks, we can safely skip this ingredients and have one less worry, when cops show up in our dark room.

If you can't obtain Acetic Acid 80% in your country, use whatever concentration you can buy and do the math.

All three formulas will be mixed as follows:

mix all components in given order

the solution will be very acidic and a white PDTA precipitate will appear

Slowly add NH3 solution. pH will shoot up initially, but will go down to ~1 again until all the PDTA is dissolved

Keep adding NH3 until all the PDTA is dissolved and until target pH is reached

Do not overshoot NH3, because if that soup ever becomes alkaline, it will precipitate Ferric Hydroxide, which is difficult to dissolve again.

Is there any specific reason to use NH3 to reduce pH compared to something more common like soda?

Rudeofus · Jun 6, 2022

minh0204 said:
Is there any specific reason to use NH3 to reduce pH compared to something more common like soda?

NH3 has some solvent property, which speeds up bleaching (PE said "a good bleach is a weak BLIX"), and it is a much smaller ion than hydrated sodium or potassium ions, therefore diffusion is much faster.

PS: NH3 is used to raise pH, not to reduce pH.

yoso20 · Jun 27, 2022

Hi Rudeofus,

Thanks for the reply!

What is the usage for 2,4-Dihydroxybenzophenon? Is it safe to just skip this ingridient? Also, if you mention that we don’t need nitrate for modern plastic tanks, do we really need Fe(NO3)3 * 9H2O for the official Kodak bleach recipe then?

Thanks!

Rudeofus said:
@koraks: while this formula does indeed contain a trace amount of PDTA, its bulk bleach component is Ammonium Ferric EDTA. Likewise the formula posted by @Murray Kelly is based on Sodium Ferric EDTA, which is even slower.

There are 3 recipes I can add to this discussion, which are based on Ammonium Ferric PDTA:

1.) Kodak Bleach III for C-41 RA process. This is a very concentrated and fast acting version (RA means rapid action) and was published in the patent US6649331:

PDTA 113.6g
2,4-Dihydroxybenzophenon 0.95g
Acetic Acid 80% 64.4 ml
NH4Br 94.67 g
Fe(NO3)3 * 9 H2O 136.93

water ---> 1000ml, use NH3 solution to bring pH up to 4.5.

2.) PDTA bleach based on Konica patent US6225018:

water 700ml
Ammonium Ferric PDTA 125g
EDTA 2.0g
NaNO3 40g
NH4Br 150g
Glacial Acetic Acid 40g

water ---> 1000ml, pH ----> 4.4

3.) My personal Ammonium Ferric PDTA based bleach. It is a lot less concentrated than the Kodak and the Konica formula, and it avoids freak ingredients:

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

Add NH3 solution to bring pH to 4.2, then add water to make 1000ml. If you have access to Fe(NO3)3 * 9 H2O, you can replace the Ferric Chloride 40% w/w solution 1:1, i.e. with the exact same weight. The nitrate used in the patented bleaches is there to protect stainless steel tanks. Since we mostly use plastic tanks, we can safely skip this ingredients and have one less worry, when cops show up in our dark room.

If you can't obtain Acetic Acid 80% in your country, use whatever concentration you can buy and do the math.

All three formulas will be mixed as follows:

mix all components in given order

the solution will be very acidic and a white PDTA precipitate will appear

Slowly add NH3 solution. pH will shoot up initially, but will go down to ~1 again until all the PDTA is dissolved

Keep adding NH3 until all the PDTA is dissolved and until target pH is reached

Do not overshoot NH3, because if that soup ever becomes alkaline, it will precipitate Ferric Hydroxide, which is difficult to dissolve again.

quiver · Jun 27, 2022

Murray Kelly said:
In the BJP Annual 1975 the formula for Kodacolor II bleach is

Sequestrene Na Fe ...... 100g
KBr ......50g
Ammonia 20% 6ml
Water to 1L
pH 5.9 - 6.1 4m20sec @38C +-3C

I use strong household ammonia (cloudy) and the Manutec iron chelate is the cheap EDTA sodium salt at USD10 for 300g.
I added NH4Cl to the KBr and I think it is faster and amm. Br could well eliminate both ammonia and KBr. I give it longer.

How much ammonia chloride do you use in your formula? Been using the un modified formula with satisfactory results, but faster bleach times with a slightly modified formula would be nice.

Rudeofus · Jun 27, 2022

yoso20 said:
Hi Rudeofus,

Thanks for the reply!

What is the usage for 2,4-Dihydroxybenzophenon? Is it safe to just skip this ingridient? Also, if you mention that we don’t need nitrate for modern plastic tanks, do we really need Fe(NO3)3 * 9H2O for the official Kodak bleach recipe then?

Thanks!

I don't know, why they put 2,4-Dihydroxybenzophenon into bleach. It might be a competitive coupler to prevent bleach stains, but I really don't know for sure. The Ferric Nitrate serves two purposes:

Supply of ferric ion to form Ferric PDTA complex
Supply of nitrate ion to protect stainless steel

Since we don't really need #2, I have used Ferric Chloride, which is very easy to obtain for amateurs like me (it's used for making circuit boards). I have already provided the conversion formula from Ferric Nitrate to Ferric Chloride solution.

Murray Kelly · Jun 28, 2022

quiver said:
How much ammonia chloride do you use in your formula? Been using the un modified formula with satisfactory results, but faster bleach times with a slightly modified formula would be nice.

quiver, I dumped in a heaped tablespoonful.
50g?

yoso20 · Jul 27, 2022

Rudeofus said:
I don't know, why they put 2,4-Dihydroxybenzophenon into bleach. It might be a competitive coupler to prevent bleach stains, but I really don't know for sure. The Ferric Nitrate serves two purposes:

Supply of ferric ion to form Ferric PDTA complex

Supply of nitrate ion to protect stainless steel

Since we don't really need #2, I have used Ferric Chloride, which is very easy to obtain for amateurs like me (it's used for making circuit boards). I have already provided the conversion formula from Ferric Nitrate to Ferric Chloride solution.

Thanks for the reply! By the way, where do you usually source Fe PDTA? Is it the one from India?

Rudeofus · Jul 27, 2022

I use PDTA free acid, not Fe PDTA. I pestered a local chem dealer long enough to sell me some. Being in the USA you could try to go through Formulary or Artcraft.

halfaman · Jul 28, 2022

Rudeofus said:
3.) My personal Ammonium Ferric PDTA based bleach. It is a lot less concentrated than the Kodak and the Konica formula, and it avoids freak ingredients:

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

I miss the acetic acid quantity in your formula. Can you provide it @Rudeofus ?

yoso20 · Jul 28, 2022

Rudeofus said:
I use PDTA free acid, not Fe PDTA. I pestered a local chem dealer long enough to sell me some. Being in the USA you could try to go through Formulary or Artcraft.

If we increase the PDTA content similar to Kodak or Konica's, do you think it will be safe for us to use in minilab machines?

Rudeofus · Aug 4, 2022

yoso20 said:
If we increase the PDTA content similar to Kodak or Konica's, do you think it will be safe for us to use in minilab machines?

Minilabs are a completely different story, since they use replenished chems. you'd have to formulate a replenisher, and you'd have to verify complete bleaching. If you go through such high volume, isn't commercial bleach III by far the cheapest and easiest way to reliable bleach your film?

BTW you should tell us, whether you'd run regular or rapid access process.

albada · Aug 5, 2022

Rudi, you did not have the quantity of acetic acid in your formula in posting #4. Could you post the complete formula?

Rudeofus · Aug 6, 2022

albada said:
Rudi, you did not have the quantity of acetic acid in your formula in posting #4. Could you post the complete formula?

Wow, how could I miss this? Sorry to all, but I am out of town now, so no access to my book of formulas this month

The main purpose of the Acetic Acid is to provide an adequate buffer at the target pH, so most likely 10-20 g/l would be a good start.

yoso20 · Aug 11, 2022

Rudeofus said:
Minilabs are a completely different story, since they use replenished chems. you'd have to formulate a replenisher, and you'd have to verify complete bleaching. If you go through such high volume, isn't commercial bleach III by far the cheapest and easiest way to reliable bleach your film?

BTW you should tell us, whether you'd run regular or rapid access process.

I understand. Thing is, not sure what happened to Kodak but the availability of their bleach is very, very bad. I cannot simply risk running out of bleach and unable to run my business at all. There's one company that's making it however the cost is significantly more than Kodak's. We're using RA bleach.

mohmad khatab · Aug 11, 2022

PDTA, FeCl3, NH4Br
These are evil items,,,,, being very expensive.
If you want to develop films at home, I advise you to buy Kodak or Fuji or even Bellini, or any other brand of bleach and chemistry.
Believe me, if you calculate the true cost of developing a single film, you will find that buying the original chemistry will be cheaper than buying those evil elements (PDTA, FeCl3, NH4Br).
)
There are other suggestions for making an excellent, very cheap, and standard bleaching product. But according to the thread title, you raised a specific question, so I should not make suggestions far from the main question of the topic

koraks · Aug 11, 2022

mohmad khatab said:
If you want to develop films at home

Be that as it may, it seems to me that @yoso20 is running a commercial operation, so I'm not sure your advice really applies to him. I'd be very cautious in any case trying to cut too many corners.

Instead, it might be worthwhile looking into availability of Fuji's RA bleach products; no doubt these are harder to get in the US than they are in the EU, but as a second source/alternative to Kodak in times of drought, it would seem like an obvious workaround.

mohmad khatab · Aug 11, 2022

koraks said:
Be that as it may, it seems to me that @yoso20 is running a commercial operation, so I'm not sure your advice really applies to him. I'd be very cautious in any case trying to cut too many corners.

Instead, it might be worthwhile looking into availability of Fuji's RA bleach products; no doubt these are harder to get in the US than they are in the EU, but as a second source/alternative to Kodak in times of drought, it would seem like an obvious workaround.

,

Even if the main objective of Mr. (O.P) is a commercial objective... Here we must pause and ask an inquiry.
The goal of traders in the sense of what?
In my personal opinion, making the original bleach by hand is completely uneconomical.
The elements that I call the "evil elements"... PDTA, FeCl3, NH4Br are very expensive, unless he can buy huge quantities (not less than 50kg of each element) in order to get wholesale prices.
This is very complicated and requires a huge investment of money.

Conclusion: My advice is that the cost should be calculated accurately, and the cost of Bleaching Roll Film should be known

JunoChan · Jul 23, 2023

koraks said:
谷歌找到了这个（帖子#2）：https://www.photrio.com/forum/threads/c41-formulas.142062/

我想就在线发布的公式而言，这已经是最好的了。

But Flexicolor III bleach have starter ... What is the starter formula？

Rudeofus · Jul 24, 2023

JunoChan said:
But Flexicolor III bleach have starter ... What is the starter formula？

This is what Kodak used in their R&D facility, so this is already working solution.

yoso20 · Dec 15, 2023

Rudeofus said:
This is what Kodak used in their R&D facility, so this is already working solution.

Hey Rudeofus,

Do you know if we can make Fe Ammonium PDTA for the second recipe you shared if we have PDTA? If so, what compound is needed?

Thanks!

Rudeofus · Dec 15, 2023

yoso20 said:
Do you know if we can make Fe Ammonium PDTA for the second recipe you shared if we have PDTA? If so, what compound is needed?

Kodak made pure Ammonium Ferric PDTA from PDTA, Ferric Oxide and Ammonia, but this was a wild process with lots of heat and pressure. I've tried doing this in my own cabinet (at room temperature, of course), and the Ferric Oxide never dissolved even after years.

Within amateur means you need PDTA, FeCl3 and Ammonia, and you will create a mix of Ammonium Ferric PDTA and Ammonium Chloride. The Ammonium Chloride won't really hurt your bleach.

C41 PDTA Bleach Recipe

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