Color negative developer near to C41

[stefan4u]

Here we go again…

With some curiosity I checked different websites for colour negative developer formulations and some time ago I’ve posted (a bit cheeky) variations of developing solutions (which aren’t very well…). Very most public formulations are suspicious similar to formulations can be found in various patents by Kodak and Fuji concerning stability / speed / amount of concentrates of colour developers solutions. These formulations include typically CD4 0,015mol /Litre (4,38g/L) 1,3g NBR, 12mg KJ and a Ph of 10.00 (of course Potash ~30-37,5g, HAS ~2g, Sulphite ~4g, and chelating agents are present too)
Developer of that kind is (in my eyes) only for research and meant as a comparative to set a stable basis. They do work, but not as a genuine C-41 developer should work. Even if the densitometer’s readings for speed and contrast for blue and green are partway OK, the red channel suffers badly. Taking some time to burrow through these scripts and search for changes in D.min/max under different formulations will show that too.

Problems and Pitfalls:

The bottom red sensitive, cyan coupling layer(s) do need more developing agent as usually listed.
The middle green sensitive, magenta coupling layer(s) behave quite well but:
The top blue sensitive, yellow coupling layers tend to be underdeveloped.


Increasing the amount of CD4 in increments till 5,9 g/Litre (max. 6.2g) leads to an overall rise of density and contrast in an undesired manner. (You may remember, that’s the “photo techniques” formulation, all other found formulations are wrong as well (4.4/ 4.5/ 4,7/ 4,8 and 5g CD4))

Than the spec. density of the solutions came into my mind, the usual 37.5 till 38 g /ltr. Potash leads (in my eyes) to an excessive diffusion pressure of alkali into deeper layers.

The ph, with it’s most magnitude of influence has to carefully adjusted, usually at about 10.00 +/- 0.05 at 25°C (in the research /comparative formulations). For non chemists, equipped only with a quite simple pH meter, this is not a fun!!
Forgetting the factor of maybe insufficient measuring equipment, I suspect this pH of 10.00 is too low.

The amount of bromide is very important too, it does affect the first layer(s) more than the middle or bottom layers, which stay under influence of bromide, released by developing the surrounded layers. Bromide concentrations usually are given in mol/Litre. Be aware that KBR has to multiply by 1.16 due the different molar weight, if NBR is requested in a formulation!!

Iodide (KJ) is till now 12mg/ltr. From former experiments with E-6 homebrew I know that blue-yellow axis can be controlled (within limits) via the iodide concentration in the FD, as well as in the CD. Maybe that’s typical only for E-6, and having read in PE’s valuable posts that the interimage effect and as a result sharpness is affected by iodide too, I’m till now a bit reluctant modifying the KJ dose.


By the way, I’m doing tests with dry prewarm and wet prewarm /prewash. Since ever I’ve done a prewash, goanna stop this now. Diffusion speed for developing agent / alkali is increased for the cyan and magenta layers, R-G show an observable shift.

So this is a funny game between pushing and pulling components, diffusion speed, and pH. At least the temperature stay’s constant…

My last tests (No.19 – 22) were encouraging, the colour curves match well, exception still a slight but quite constant decrease of red. If using a prewash the results are very close to a former probe, developed with Flexicolor (prewashed too) but still different from my “reference minilab”. Maybe this is mainly the difference between rotary tube and leader card / or continuous developing machines, never have checked that before.

… a week later…

Anyway, after some nights in the dark, some thinking, spreading sheets of paper all over the flat, I’ve found a formulation that works VERY WELL.

Very well means he colour curves shift not more than 0.09 from the green base. This is for the white pattern (HD) from the “Jobo test Chart” that one with 6 grey levels, RGB and CMY Patterns. This nearly reaches my minilab DIY reference.

Density of HD is good, film speed either.
I’m goanna try to load a scan of my densitometry values, but be aware, this is no conventional C-41 plot, I do it the way I do it for chromes too… values in braces are absolute, the other RGB values for field 1 till 6 are already subtracted from Dmin…






This is the VERY BEST result so far, works much better than all other formulations I’ve ever tested. I call it C-25, for test run 25

Here the formulation so far. In order to avoid the subsequent pH correction with sulphuric acid or KOH (which is a must-do in all formulations) I will try to include a carbonate/bicarbonate buffer system at the next run, but this may take some time...


800ml Tab water
1 ml Orwo A905 (wetting agent, can be omitted)
2 g Calgon
29g Potash (28 till 34 g are OK)
4g sodium sulphite
1.5 g potassium bromide
12mg Potassium iodide
2.5 HAS
5.2 CD4
Up to 1 Litre
pH adjusted with KOH or sulphuric acid to 10.11 at 25°C
Spec. gravity reads 1.035

As you may see it would be make sense to increase CD4 in a very small fraction (maybe 0.1 till 0.15 grams, than maybe reducing the ph carefully to maintain HD at about 1.00

If you are in some homebrewing, try this, you will not regret it.


Comments welcome,
Regards from Germany,
Stefan

 

[stefan4u]

There is a typo in the above formulation,
1.2mg KJ has been used, not 12mg!!

Regards,
Stefan

 

[AgX]

Congratulations!

Quite a laborious experiment.

-) it is always fine to have a working formula at hand from which to deviate for specific experiments.
-) for those of us who undergo difficulties in obtaining industry C-41 chemistries, a formula for a homemade developer could be a solution
-) some may consider doing so just for cost-effectiveness



But keep in mind that Flexicolor sets the standard to which other companies have to design their films as long they want them to be processed with good results in chemistries who follow this standard.
Thus films are optimized for a given process.
(In theory there might be a C-41 film being processed in a custom made developer bearing even better result than Flexicolor.)

You however designed a developer for a given film.
It could be that with another film your results would not be that much in line with Flexicolor.
Thus any comparative tests should be done with several types of C-41 films being processed.
(I do this remark as you did not state how you ran your tests. Perhaps you already did so.)


Seemingly this is a one-shot process at the moment.
Are you thinking of doing several runs (time compensated or replenished) in future?

How do you do the `dry pre-warm´? Just by letting the drum with film rotate for a while in the warming bath? Or do you use temperated air?

 

[stefan4u]

Dear AGX !!

Definitely I do now that Flexicolor sets the standard, and I love it very much. Developers of other brands tend to give more contrast, this may be well in some situations, but gave me often difficulties during enlarging.

I’ve done all this only to satisfy my curiosity about possibilities and probabilities of ingredients. Further there simply waits some stuff to be used .

You are absolutely right, this is only for this type of film tested, and others may behave different. It’s only a hobby; I don’t have to earn my bread and butter this way.

It’s used at a one way developer till now, just to reduce the variables. Replenishment seems not to make sense in the home darkroom, because of the lack of regular usage / regular “tank turnover” and intensified oxidation during drum processing.
But the developer is not specially designed as one way, it’s not a “thinner one”, so reuse for one run should be OK with slightly prolonged time (~3:25 min.). As usual, use at least 200 - 250 ml for one film (135/36) and at its best at least 500 ml for better Temperature consistency in one run.

That leads to your other question, the prewarm. As mentioned above I measures surprising differences in colour curves when using the prewetting/ wet prewarm. These differences are not stringent visible in a print, but one of the fluctuating influences I would like to skip. So a proper dry prewarm in temperate water / in the Jobo processor for about 20 min. in low volume clip developing conditions (200 ml) is necessary. As the volume of the developer increases it’s stability against temperature loss will increase too. Shorter dry prewarm times should be possible then …




By the way “C-26” is on schedule with three changes :

Minor decrease of sulphite to allow the lower densities so develop a touch more (from 4 to 3.5g).
Minor increase of KBR (1,5 g to 1.7g) and KJ (1.2mg to 1.4 mg) to limits highlights
The amount of CD4 stays at 5.2g , this is quite well working.
Some buffer capacity for easy pH calibration is planned by adding
bicarbonate. Readjust amount of potash for that…

Regards from Germany,
Stefan

 

[Photo Engineer]

IIRC, the pH is correct at 10.1, but the bromide seems too high, but I may be wrong. I have forgotten too much!

All salts in the Kodak formula are Sodium salts and no potassium salts are used except for KI (KJ in German). So it is Sodium Carbonate and Sodium Bromide, etc..... Calgon is no longer used. Kodak uses Quadrofos or Dequest.

I think the carbonate is low in your formula. That would cause low contrast.

PE

 

[stefan4u]

Dear PE !!

Thank you for „logging in“ , the ph at around 10.1 really works better than a ph above 10.00 or10.05. That’s something I couldn’t believe at first but looks proven now… The used bromide is potassium bromide, 1.5g are roughly equivalent to 1.3g sodium bromide.

The usage of more effective anti chelating agents, like quadrofos or other EDTA salts, as you mentioned, will be better for sure. But we live in a region with quite soft water (haven’t delimed my teakettle for years) and longer shelf life of mixed product is not indented anyway.

About the carbonate….
This is something still mysterious, I’m still testing. But adding nearly 40g Potash alone plus all the other ingredients will inflate the gravity of the developer. I’m aware that data sheets are more intended to keep secrets, but there are a few things in common if you put some side by side.
Flexicolor SM claims to have something about 18 till 22 g potash/litre combined with bicarbonate 3.6-7.4g7Litre. Flexicolor developer replenisher is stated with 22 -26g/Litre (diluted working tank solution), then next a “one phase” colour developer (Prime?) is stated with 23 g/L potash and 6,6g bicarbonate (all potassium). Is this coincidence that the amount of alkali salts is given at about 30g/Litre ??

Anyway, I brewed up a solution with 24g potash (which was in fact low in contrast) and with 34 g potash/ Litre, wich was fine). Each half of unused solutions was mixed together that’s why “C-25” does have 29g Potash; the difference is measurable but marginal.

Just this moment the Jobo fires up, prewarming the next batch, which do have 32 and 33g potasch/Litre and 1.5g sodium bicarbonate. Personally I do prefer more a soft working developer, the last edition was very close to desired.

Well’ see what happens…

Regards from Germany,
Stefan

 

[Photo Engineer]

IDK why, but the NaBr is still high to me, but again, I may be wrong here. I also know that a carbonate series in the developer gives a contrast (gamma) series in the 3 layers. It is a matter of buffer capacity in the bottom layer making the cyan drop off faster. I seem to remember more carbonate than that. I'll have to test one of my patents, but IIRC, the carbonate in C-22 and C-41 were almost identical.

PE

 

[stefan4u]

Hello again!

“C-26” was a partway success , setting the pH with a combination of Potash and sodium bicarbonate works well so far.

To be concrete:

1ml A905
2 g calgon
32 g potash
1.5 g sodium bicarbonate (has to be weigh out accurate!!)
3.5 g sulphite
1.7 g KBR
1.4 mg KJ
2.5 g HAS
5.2 g CD4

leads to a pH of about 10.12

Increasing the Potash to 33 g/Litre gave me a pH of 10.14/10.15 .

Because of working densitometer but rather “budget” ph meter with gel electrode, not approved for reductive photo chemicals, I do settle a measured ph of 10.14/15 at 25°C as my “aim”.

Here is the bad news: Increasing the KBR and the KJ leads to the wrong direction, although reducing the sulphite, I lost about 1/3 stop (0.05 D). Balance of the Colour curves is untouched and still very good.

Anyway, will use the residual “C-26” solution and do some more testing for slightly increased dev. Time and maybe again a prewash. The formulation is as close that I dare

“C-27” with (again) slightly reduced KBR / KJ and maybe slightly upscaled CD4 (with necessarily upscaled potash) will follow…

Regards from Germany,
Stefan

 

[stefan4u]

Yesterday I brewed another batch, “C-27” and it turned out to be very close, I don’t think home brewing can get any closer!



CD4 was increased to 5.3 g. Because of more acidic developing salt potash has to be increased as well to 34 g/ litre

Potassium bromide was reduced in increments, 1,4 g/Litre seems to be the optimum amount.

Potassium iodide was reduced again to 1.2 mg/Litre.

Compared to “C-26” HAS was reduced to 2 g/Litre, and again a pH adjustment was necessary (grumble…) This time I increased the Sodium bicarbonate (Baking Soda) in increments up to 1.9g/litre lo maintain a pH of 10.16

Developed clips where near perfection, high density regions as well as low density regions. Full film speed is reached, with steady going range of contrast. Because of beneficial influence of KJ in an amount of 1.4mg/litre in a former run, I just topped again 0.2mg/litre to the existing 1.2mg.

The Jobo is prewarming now, but because of excellent former clips I dare to jump into the cold water and have filled a tank with 5 Films 5 x 135/27exposures (equal to 4 x135/36 exposures)

This is my final developing solution: “C-27”

800ml tab water
1 ml A905
2g Calgon
34g Potash
1.9g Sodium Bikarbonate
3.5g Sodium Sulphite
1.4 g Potassium bromide
1.4 mg (!) Potassium iodide
2g HAS
5.3g CD4

Up to 1 Litre,
Measured pH is 10.16 at 25°C. As stated somewhere above the ph meter is a cheap one, so there may be a variance, suppose it’s around .03 till .05

BUT whatever you do, pH has to be above 10.11 (measured with my unit 10.13), there is absolutely no chance to get a proper developed film with lower pH! Red will suffer badly!

Therefore be accurate if scaling the ingredients, especially Bicarbonate and Potash, HAS and CD4. This formulation is intended to work without pH adjustment, that’s why I included the bicarbonate buffer. If proper ph measurement is available you may vary a bit, but have to readjust the ph again.


Hours later...
Uuups … :confused: Just measured the 5 films out. There seems to be a temperature inconsistency. It’s a different about 2/3 stops weather multitank 2 (with its volume of 270 ml) is used or the multitank 5 filled with a whole litre. Seeing this, I remember why I preferred the wet prewash for so long time…



Anyway, a multitank 2, combined with a dry prewarm and about 250 ml (one film) of developer works definitely fine. The processors water jacket temperature is set to 38.4°C since ages; have to measure the difference of the temperature, after a minute or so, direct in the drums. Sadly my holidays are over, prints have to wait too.

Regards from Germany,
Stefan

 

[stefan4u]

Really don’t want to bore anybody, but some words to disclose that …

Because of the (always again) surprising influence of temperature drop during dry prewarm, versus inertia of bigger volumes I looked up through my negatives to find more comparatives.

I’ve found films developed with Tetenal at 30°C for 8 min. which show a stronger overall colour deviation, that means colour cross over (magenta/green cast in the greyscale). But I’ve been able to enlarge quite good prints from these films, adapting the filtration that way these colour errors are more in the dark aereas…

The time I’ve got Flexicolor in my hands, time of experiments began again. I tried different times (actually not too different, in the region of 3:20 till 3:30), dry and wet prewarms, all at my usual 38.4 °C . All data can’t be recovered, but consistency increased with bigger volumes, the last 2 years I always took as much as possible developer (~1Ltr/ for 5 or 6 Films).
Worth remarking is that my usual proceedings (Drum processing, Flexicolor at 38.4°C jacket bath temp. for 3:20 min with a wet prewash gave me wonderful negatives. But the overall error is surprisingly higher (!) than with my actual home brews. For the most part this will be the influence of prewetting, (next to exceeding temp). But the error is not visible in, let’s say most prints (I’m attempted to say it’s not visible at all).

If you want to try “C-27”, decrease temp about 0.5°C for amounts bigger than 250 ml (that is exact the temperature it should have) and maybe better use always the same drum / same number of reels / same amount of developer to get everything in control.

Regards from Germany,
Stefan

 

[ahock]

Dear Stefan,
I intend to run the same test film at my site. I don't have Jobo test pattern. Do you know any other method to prepare the test film for the color balance test? Thanks!!

Best,
ahock

 

[newcan1]

"C27" Trial

Well having tried various unofficial formulations of C-41, most coming up with thin negatives, I tried the "C-27" formula presented here. I don't have a color densitometer or anything, but the negatives came out looking awesome, and they scanned nicely. I have not done any darkroom prints of them yet. But this seems to be a really good formula and delivers negatives of good density at the film's full rated speed. I am excited to see how darkroom prints come out.

 

[Rudeofus]

First of all, thanks a lot, stefan4u, for posting all this and going through all the effort researching this. Luckily we still get C41/E6/RA4 kits for small scale home users but I wonder when that will change. I would suggest that this ends up in some sticky thread where we collect all these formulations, especially the tested and proven ones. I recommend to all people who want to start experiment that they contact APUG member mts, he has a very fine collection of formulations for C41/E6/RA4, which should at least provide a starting point for optimizations.

Could someone more knowledgeable than me add the following info here?

• Full official names of the chemical compounds listed, also possible ways of obtaining them.
• Toxicity information about these chemicals, safe handling procedures. This has already been discussed (there was a url link here which no longer exists).
• Possibly some info about longevity of the compounds and possible storage recommendations. I'm not sure whether CD4 has other uses beyond color film development and how easy it is to synthesize.

Remember that this kind of work is more important than all the dreading over film discontinuation. We (at least the hobbyists) can easily stock live time supplies of our favorite film stock in a freezer but all this won't help us if we suddenly lose access to dev process, ask the Kodachrome lovers here.

PS: Here is my minimal contribution:

• CD4's official name is "4-(N-Ethyl-N-2-hydroxyethyl)-2-methylphenylenediamine sulfate", CAS number 25646-77-9
• HAS is "Hydroxylamine sulfate", CAS number 10039-54-0

 

[Mike Wilde]

Well ,some of the challenges to mixing at home depend on getting the chemistry. The Formulary stocks HAS, but cannot mail it outside of the US.

I have a good stock of CD-4, which they can mail me. It is nothing to dream about fabricating at home.

Read up on the history of a dye maker, that a few years ago, shut down in Buffalo NY. I saw the ongoing demolition and clean up efforts as a part of a trip there last weekend.

It went by a series of names in the almost 100 years it operated. The longest lived name I think was National Analine. Its final name was Buffalo Color.
The steps to fabricate some of the dyes, as well as the feedstock volatility and flamability issues are mind boggling. To think that a lot of this was worked out by the 1920's has amazed me.

With color photography what we essentially are doing is splitting the dye so that the second half is the oxidation component of the color developing agent.

 

[SSHA]

First of all, thanks a lot, stefan4u, for posting all this and going through all the effort researching this. Luckily we still get C41/E6/RA4 kits for small scale home users but I wonder when that will change. I would suggest that this ends up in some sticky thread where we collect all these formulations, especially the tested and proven ones. I recommend to all people who want to start experiment that they contact APUG member mts, he has a very fine collection of formulations for C41/E6/RA4, which should at least provide a starting point for optimizations.

Could someone more knowledgeable than me add the following info here?

• Full official names of the chemical compounds listed, also possible ways of obtaining them.
• Toxicity information about these chemicals, safe handling procedures. This has already been discussed (there was a url link here which no longer exists).
• Possibly some info about longevity of the compounds and possible storage recommendations. I'm not sure whether CD4 has other uses beyond color film development and how easy it is to synthesize.

Remember that this kind of work is more important than all the dreading over film discontinuation. We (at least the hobbyists) can easily stock live time supplies of our favorite film stock in a freezer but all this won't help us if we suddenly lose access to dev process, ask the Kodachrome lovers here.

PS: Here is my minimal contribution:

• CD4's official name is "4-(N-Ethyl-N-2-hydroxyethyl)-2-methylphenylenediamine sulfate", CAS number 25646-77-9
• HAS is "Hydroxylamine sulfate", CAS number 10039-54-0

@Rudeofus
Did the collective thread of tested formulations happen? I checked the sticky threads in the parent forum but couldn't find it. Please advise.

 

[Rudeofus]

@Rudeofus
Did the collective thread of tested formulations happen? I checked the sticky threads in the parent forum but couldn't find it. Please advise.

That collection unfortunately never materialized. I will post a brief collection of links here, in hopes that it survives longer than previous link collections:

1. C-41 developers
1.1 Grant Haist's C-42 formula, which can be mixed from easy to get ingredients, but working solution lasts only a few weeks
1.2 There is US patent 6649331, which supposedly gives an accurate C-41 formula.
1.3 Ron Mowrey posted formulas which he claimed are the original formulas. DTPA is hard to obtain, but maybe we can push Suvatlar and Wilson to finally list it, maybe together with phosphonic acid based sequestering agents
1.4 Stefan Lange posted two formulas: C-27 for rotary development with a water jacket at 38.0°C, and C-29 for rotary development with slightly higher water jacket temperature to keep the developer inside the tank at 38.0°C. His formulas use easy to obtain ingredients.
1.5 There is a Konica patent, which uses proper sequestering agents and also comes with a replenisher formula.

Will post E-6 formulas in a separate posting here.

 

[Rudeofus]

2. E-6 developers
2.1 Watkins' Factor formula and here is allegedly not a good formula, but its ingredients are fairly easy to obtain. Every thread about E-6 homebrewing typicallly starts with this formula, so it's listed here for completeness reasons. Never tried it myself.
2.2 Stefan Lange's Homebrew Chromebrew formula: also made from fairly easy to get ingredients, but more expensive to mix that Derek Watkins' formula. More closely resembles original E-6.
2.3 There is US patent 6617099 by Fuji, which lists a complete set of formulas for working solution. It is discussed here. The compound Nitrilo-N,N,N-trimethylene phosphonic acid pentasodium salt denotes ATMP Pentasodium Salt aka Dequest 2006, a strong sequestering agent.
2.4 There is US patent 5948604 by Kodak, which lists a complete set of formulas for E-6 liquid concentrates. It contains several compounds which are difficult to obtain.

PS: I have tries all of these C-41 and E-6 formulas except for Watkins's Factor, and everything I tried worked reasonably well. Formulas without strong sequestering agents (Calgon, EDTA or nothing instead of DTPA or ATMP) have short shelf life (2-3 weeks), the Kodak concentrates last quite long in glass bottles. Since E-6 bathes are quite tedious to mix, I recommend you find reliable sources for DTPA and ATMP.

 

[SSHA]

That collection unfortunately never materialized. I will post a brief collection of links here, in hopes that it survives longer than previous link collections:

1. C-41 developers
1.1 Grant Haist's C-42 formula, which can be mixed from easy to get ingredients, but working solution lasts only a few weeks
1.2 There is US patent 6649331, which supposedly gives an accurate C-41 formula.
1.3 Ron Mowrey posted formulas which he claimed are the original formulas. DTPA is hard to obtain, but maybe we can push Suvatlar and Wilson to finally list it, maybe together with phosphonic acid based sequestering agents
1.4 Stefan Lange posted two formulas: C-27 for rotary development with a water jacket at 38.0°C, and C-29 for rotary development with slightly higher water jacket temperature to keep the developer inside the tank at 38.0°C. His formulas use easy to obtain ingredients.
1.5 There is a Konica patent, which uses proper sequestering agents and also comes with a replenisher formula.

Will post E-6 formulas in a separate posting here.

Thank you, this is really helpful.