Current Options for DIY C-41 Chemistry?

[RPC]

From what I understand, no, the exact formula has not been published since it is proprietary. But there are some that come close in various patents, and even here on APUG and perhaps other sites. But my point of view is that if you mix your own, the exact formula is not necessary if you find a formula that meets your needs.

 

[Rudeofus]

Is the official c-41 formula published anywhere? I looked for it for some time before I gave up...

The is an official formula listed in US6649331.

 

[RPC]

The is an official formula listed in US6649331.

But is this official Kodak formula?

 

[fdonadio]

.But my point of view is that if you mix your own, the exact formula is not necessary if you find a formula that meets your needs.

I have to agree with you on that! But, of course, if the "real thing" was available, I would prefer it...


Cheers,
Flavio

 

[fdonadio]

But is this official Kodak formula?

Have you guys noticed the patent has expired in 2012? There's a note in the end of the page that Rudeofus linked to: "Expired due to failure to pay maintenance fee."


Cheers,
Flavio

 

[StephenT]

Then it would appear that the formula is now in the public domain. Might not someone start up a color kit distribution company in their basement?? Or like Microsoft, in the garage??

 

[RPC]

I don't think I would trust any published formula to be the real thing unless Kodak actually said it was, which I don't think is going to happen. But again, there are very good formulas out there known to give results virtually indistinguishable from the Kodak formula (Flexicolor). I have one somewhat different from the above link I will post if you want it, fdonadio.

 

[Rudeofus]

Have you guys noticed the patent has expired in 2012? There's a note in the end of the page that Rudeofus linked to: "Expired due to failure to pay maintenance fee."

That formula was not part of the claims, therefore the patent never protected that one formula.

 

[fdonadio]

I don't think I would trust any published formula to be the real thing unless Kodak actually said it was, which I don't think is going to happen. But again, there are very good formulas out there known to give results virtually indistinguishable from the Kodak formula (Flexicolor). I have one somewhat different from the above link I will post if you want it, fdonadio.

Since Photo Engineer said the formula in the patent is pretty close to the production formula, I'll go with that.

I'm looking for all the components and I'm sure it will take some time to source them all.


Cheers,
Flavio

 

[fdonadio]

That formula was not part of the claims, therefore the patent never protected that one formula.

I didn't mean that the patent applied to the formula, but it's kind of curious to see a patent expire for that reason, even if Kodak is going bankrupt...

From what I understood, the patent applies to a technique for shorter development times using some kind of polymer and reduced iodide.

The C-41 "formula" is there for mere comparison. And both formulas (C-41 and "polymer-based rapid developer") may be incomplete.

Even though PE said this formula is "close", he has warned about incomplete formulas in patents a bunch of times in the past... It may or not be the case, as PE won't say what's wrong with the formula (as he would be revealing his former employer trade secrets). And, from what I understand, PE can't guarantee that the formula he had access (?) is still in production.

So, we will never know, unless Kodak publishes the formula officially.


Cheers,
Flavio

 

[Rudeofus]

The C-41 "formula" is there for mere comparison. And both formulas (C-41 and "polymer-based rapid developer") may be incomplete.

We can safely assume that there is some sequestering agent for water hardness in the commercial formula. You can mix the formula from the patent with distilled water, though.

Stefan Lange did a long series of tests with control strips and published his formula here on APUG in a link that RPC already posted here in this thread.

 

[Rudeofus]

Then it would appear that the formula is now in the public domain. Might not someone start up a color kit distribution company in their basement?? Or like Microsoft, in the garage??

There are some companies that make C-41 kits geared towards amateurs, so that market segment is well covered. Yes, most of these kits use BLIX, but there are ways to convert these kits to use separate bleach&fix steps.

 

[RPC]

Since Photo Engineer said the formula in the patent is pretty close to the production formula, I'll go with that.

I do recall a thread where PE posted about a formula being close to the Kodak production formula. If I am thinking of the correct thread, it was in response to a formula I posted, that does not appear to be the same as the one in Rudeofus's link. Mine was found in patent US5827635. It is the one I offered to post for you in the above post. I have tried it and got good results.

 

[fdonadio]

I do recall a thread where PE posted about a formula being close to the Kodak production formula. If I am thinking of the correct thread, it was in response to a formula I posted, that does not appear to be the same as the one in Rudeofus's link. Mine was found in patent US5827635. It is the one I offered to post for you in the above post. I have tried it and got good results.

Great! Keep those formulas coming, then!

I have collected some formulas and thought about creating a table for comparing them.

I also have the "C-27" formula by Stefan Lange...

I didn't look a couple of pages back, but I think I remember PE commenting on this very same thread!

EDIT: I was wrong. PE didn't comment on this thread, but here:

http://www.apug.org/forums/forum40/104335-c-42-kodaks-home-version-c-41-a.html

EDIT 2: the above link was wrong.


Cheers,
Flavio

 

[RPC]

Yes, that was the thread I remembered, so you have the formula.

 

[Rudeofus]

Reading the original scribblings of Albert Einstein about relativity won't teach you astrophysics any better than a modern textbook. Likewise, having the correctest of all correct C-41 formulas still doesn't guarantee you accurate results:

• Do your raw chemicals have the same type and amount of impurities as Kodak's?
• Are you sure your film tank and process liquid have the correct temperature? How accurate is your thermometer?
• Is your agitation 100% consistent and equivalent to Kodak's process?
• Is your film fresh and processed right after exposure?
• Are your process times accurate and fully repeatable?

AFAIK commercial labs had to constantly monitor and fine tune their process to stay within specs, and low throughput labs were prone to all kinds of issues. If you want a high level of process accuracy, make sure you have a 100% repeatable setup, then use whatever formula which you then fine tune with process control strips.

 

[RPC]

Reading the original scribblings of Albert Einstein about relativity won't teach you astrophysics any better than a modern textbook. Likewise, having the correctest of all correct C-41 formulas still doesn't guarantee you accurate results:

• Do your raw chemicals have the same type and amount of impurities as Kodak's?
• Are you sure your film tank and process liquid have the correct temperature? How accurate is your thermometer?
• Is your agitation 100% consistent and equivalent to Kodak's process?
• Is your film fresh and processed right after exposure?
• Are your process times accurate and fully repeatable?

AFAIK commercial labs had to constantly monitor and fine tune their process to stay within specs, and low throughput labs were prone to all kinds of issues. If you want a high level of process accuracy, make sure you have a 100% repeatable setup, then use whatever formula which you then fine tune with process control strips.

That is why when I first came to this site I went to the archives and read every thread relating to color processing. I learned a great deal about what is important and what is not. I decided it was important to me to know what I was getting with my processing so bought a densitometer and use that to regularly check, and if needed adjust, the quality of my processing and experimenting. It has been very helpful in finding out what works and what doesn't, and helps keep my processing within tolerance standards. I have found that using good formulas and being reasonably diligent about the factors you mentioned, one can produce high quality results with home brew processing.

But in the final analysis everyone has their own level of acceptance, and not everyone needs a densitometer or the same level of diligence to produce what is acceptable to them.

 

[fdonadio]

Reading the original scribblings of Albert Einstein about relativity won't teach you astrophysics any better than a modern textbook. Likewise, having the correctest of all correct C-41 formulas still doesn't guarantee you accurate results:

• Do your raw chemicals have the same type and amount of impurities as Kodak's?
• Are you sure your film tank and process liquid have the correct temperature? How accurate is your thermometer?
• Is your agitation 100% consistent and equivalent to Kodak's process?
• Is your film fresh and processed right after exposure?
• Are your process times accurate and fully repeatable?

AFAIK commercial labs had to constantly monitor and fine tune their process to stay within specs, and low throughput labs were prone to all kinds of issues. If you want a high level of process accuracy, make sure you have a 100% repeatable setup, then use whatever formula which you then fine tune with process control strips.

I don't understand if this is meant to be a reply to me. If it is, maybe I am not expressing myself correctly (English is not my first language, so this is very likely)...

Repeatability, control of chemistry temperature and pH, control of other lab's environment variables and developer technique are all crucial factors in color film development, from what I know. So, I think we all agree here.

My point is: I, too, am not a chemist... But I want to make sure that my negatives will be in good shape for the next couple of decades, at least. So, let's assume my process is fine-tuned and repeatable, and my technique is perfect. The only remaining factor is chemicals quality!

I know I can assure the quality of my work by buying Kodak's or Fuji's chemicals. But it's not even close to easy to buy chemicals in Brazil if you're not a professional lab. Also, pro labs need government authorization to store and manipulate chemicals in "large" quantities, and Kodak and Fuji don't offer smaller kits here anymore... Foreign stores won't ship these here because of restrictions... You get the picture (no pun intended).

<rant>Heck, Fuji wanted to stop offering their Pro 6 color reversal process chemicals in Brazil! And, this time, only a handful of pro labs complained! My preferred lab said their chemicals stock should last for a year now. So, I can only kneel down and pray that Fuji will import one more batch next year (and, being an atheist, I don't think it will help at all).

I am considering a future where I'll shoot only black and white, DIY plates and film and enlarge on DIY paper. All processed on DIY chemicals. But I want to be able to get color materials for as long as I can. I can still buy film at B&H or Adorama, I just can't get the chemicals here.</rant>

About chemical purity: lab supply stores carry "analysis-grade reagents" (this is a loose translation from the portuguese term), which should be close to 100% pure. Most chemicals used in photography are easy to buy, except for strong acids and bases... And even those can be bought in less concentrated solutions, which shouldn't be a problem.

So, back on the subject and concluding: the most correct my C-41 formula is, the most certain that the negatives will be good in a couple of decades I'll be. That's my point.


Cheers,
Flavio

 

[fdonadio]

Comparison of C-41-like formulas on the web

Hello, all!


I compiled this document from several formulas I've found on the web. It's meant as a simple means of comparison, for the ones that understand more about chemistry than me.

All quantities are in grams and are meant for one liter of solution (the decimal "point" in my language is a comma, so you may need to replace that! ).


Cheers,
Flavio

 

[Rudeofus]

AFAIK there are three main parameters which control whether your negs/slides can be stored for a long time without parameters:

1. Use the correct color developing agent: this means CD-4 for negatives and CD-3 for slides
2. Remove all silver and silver salts. According to PE this means use bleach&fixer instead of BLIX. It also means that bleach time must be sufficient and that fixer must have pH 6.5 and be used within its limits.
3. Use a proper final rinse, see (there was a url link here which no longer exists) for details.

Other process deviations will give you wrong contrast, saturation or color balance, color crossover, insufficient film speed in one or all color channels, incorrect Dmin and Dmax, but it will give you all that with reasonable long term stability.

 

[RPC]

I believe Rudeofus is correct. The developer used should not affect image stability as long as it uses CD-4.

 

[OptiKen]

I have only used the Tetenal C41 powdered kit and have been very happy with the results.

 

[nbagno]

I have only used the Tetenal C41 powdered kit and have been very happy with the results.

+1

 

[hjesus]

Hi! Your recipe doesn't use HAS. How long does it last or how many rolls can we develop with it?

 

[Photo Engineer]

HAS is a weak base + a strong acid. As such it affects the pH of the final solution. It is also a mild competing B&W developer and a preservative.

So, it has 3 effects on the developer regarding color crossover (pH), sharpness (competition) and overall durability.

PE