What strength ferricyanide for color film bleach?

Donald Qualls

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I'm strongly considering dropping "kit" chemicals and going back to home brewed color developer, with separate bleach and fixer steps. C-41 fixer is easy to make and still not hard to find pre-made -- it's just a neutral to slightly alkaline rapid fixer. The standard bleach, based on ferric EDTA, is a bit harder to manage. There appears to be a path via obtaining sodium EDTA and converting it, but from my reading, it appears that a ferricyanide bleach works fine and potassium ferricyanide is easy to get (I've got a tub of it on hand, in fact, purchased for cyanotype).

Question is, what solution strength do I need, how long will it take to bleach, and how much potassium bromide and/or sodium chloride will be needed in the bleach to ensure a fixer-soluble end product? I'll most likely be working at 80-85F for a Dignan 2-bath color developer, which will extend bleach time a little, but I can compensate that if someone has experience at 100-102F.
 

koraks

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I'd simply start by using the ECN-2 ferricyanide bleach for C41. Chemically ECN-2 films will be quite similar to C41 films so the ECN-2 bleach will likely work fine for C41 as well.
 
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Donald Qualls

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Okay, @koraks thanks for the reminder. Found the Kodak ECN-2 processing publication; they give 40 g/L potassium ferricyanide and 25 g/L potassium bromide; they also give a replenisher formula, though I doubt that's worth bothering with on a home process basis.
 

David Lyga

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What I have always done is this:

Make your bleach: one gram of potassium ferricyanide (or one mL because with potassium ferricyanide it is the same) per every 50mL of water. Bleach lasts indefinitely, just keep away from direct sunlight.

To make BLIX: one part bleach + one part PAPER strength (FRESH) fixer. The combination lasts at least 20 minutes.

I have always fixed the negative first in fresh paper strength fixer. Then I wash the film for a minute or two (in full room light), then I blix for about five minutes. (Do NOT use the same fixer that you used for fixing or you will get contamination). You CAN dilute this blix somewhat but then you might have to blix for up to ten minutes. Then wash the film and dry. - David Lyga
 

pentaxuser

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This is a very easy method, David and simple to use. I can see its attractions, especially if there isn't even the added requirement to use Potassium bromide on which you asked a good question. Can I ask how long you have been using this? If it is several years have you checked the films and seen any problems?

Based on a previous accusation in another thread that I ask questions when I may not have any intention of putting the method to use I should declare that this may be the case and that I ask questions in some cases to get information for the sake of satisfying my curiosity without necessarily committing to doing more about it

pentaxuser
 
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Donald Qualls

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And one reason I don't want to use blix is this -- "lasts at least 20 minutes". By using separate bleach and fixer, both will last months -- the bleach especially, as you note. The EDTA based blix lasts much better than this, but it's still limited.

I found the Kodak publication referenced near the top of the thread, and IIRC it's 40 g/L of ferricyanide and 25 g/L of potassium bromide (though I'll look at it again before I mix, because I'm not at all certain I don't have those amounts reversed). To work separately from fixer, the bromide is required to convert the silver into a fixer-soluble form; if you mix the bleach and fixer, you don't have to do this because the ferricyanide allows the fixer to directly react with the image silver, just as it would when using a similar mixture, Farmer's Reducer (which also doesn't last well once mixed). Further, I don't need two separate fixer steps, one (and a wash) before bleach, and another after; the bleach (with bromide) converts image silver back into halide and the fixer removes all the halide, whether it's converted from image silver or simply undeveloped.

Develop, stop, (optional) wash, blix, wash, final rinse from a C-41 kit becomes develop A, develop B, wash (no stop bath needed because no precise timing required, but wash prevents developer carry-over into bleach which can stain the film), bleach, wash, fix, wash, final rinse. More steps, more time, but the two-bath color developer has huge capacity and longevity, as you note the bleach lasts very well, and fixer will have roughly half the capacity it would have in B&W (because it's removing roughly double the halide). In the end, I won't have to worry about whether my chemistry has gone bad since last color film processing, and as a bonus my cost per roll (even if I were using the full capacity of a C-41 kit) will drop by about 75% or more.
 

David Lyga

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No no potassium bromide and I have not seen any problems in the interim. But the addition of the bromide does pique my interest and I might delve into some experimentation here. I was not aware (!) that the bromide facilitated the removal of the halide. - David Lyga
 

David Lyga

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Donald is this '2 step development' doable with Kodak Flexicolor? And how? I am curious here. - David Lyga
 
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Donald Qualls

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David Lyga said:
Donald is this '2 step development' doable with Kodak Flexicolor? And how? I am curious here. - David Lyga
Click to expand...

I referred to the Dignan 2-bath C-41 Color Developer I've mentioned in other threads (and posted in one fairly recently). Like B&W 2-bath developers, Bath A is slightly acidic to neutral, and little or no development takes place in it; further, its pH contributes to long shelf life. The developer that carries over from Bath A does the actual work in Bath B, which contains the alkali only (in this case, sodium carbonate with a little potassium bromide as a restrainer -- the original formula called for a small amount of benzotriazole, but I've found it works well without that). I used this developer for about a year -- a single one-liter batch -- in my old darkroom, and just got everything together to mix up a fresh batch after a trip to my local brewing supply to get potassium metabisulfite (which mainly keeps the sodium sulfite from making Bath A alkaline enough to start development).

After the color developer, one could use Flexicolor bleach and fixer -- I did, when I used it originally in 2005-2006 -- but at this time I plan to use a ferricyanide bleach followed by a neutral to alkaline rapid fixer, finishing up with genuine C-41 Final Rinse after the wash.

Here's the section on Dignan 2-bath C-41 that used to be on my web page (before my provider quit hosting personal pages):

Dignan NCF-41 -- Two-Bath C-41 Color Developer

This developer was originally published by Patrick D. Dignan in the November-December 1995 issue of Phototechniques magazine. I've modified the Bath B very slightly to use more readily available chemicals and to reflect my own experience.

Like most two-bath developers, little or no development takes place in Bath A; the developer permeates the emulsion, however, and the chemical thus carried over into Bath B does the work, developing essentially to exhaustion in the time allotted for Bath B. This makes the process relatively insensitive to temperature variations; Dignan recommends 75° F, but my experience shows that, because it develops to exhaustion, the developer works effectively the same over a range of temperature from about 70° F up to at least 85° F. Also like most two-bath systems, the Bath A has a very long life; I made up a liter initially, and have processed equivalent of about ten rolls over two months with no change in results (though I'm about to make up some more Bath A to use in replenishing the working solution, much as I'd use fresh Diafine to replenish the solutions in use). The Bath A solution does tend to discolor over time with dyes washed out of the film, but this doesn't seem to cause any change in working characteristics.

Bath B is to be used one-shot -- it contains no preservative, and in fact is essentially just an alkaline solution of the proper pH with some restrainer added to control fog. Dignan originally called out both potassium bromide and benzotriazole, but since I didn't have any benzotriazole (and the notes I found with the formula suggested Dignan had used the developer without it), I doubled his level of potassium bromide and found the developer worked fine that way. This B bath is very cheap, so it's not painful to toss it down the drain after use.

It is strongly recommended to increase bleach and fixing times over those given in the usual C-41 documentation; due to lower temperature, these baths will work slower than they would at the canonical 100° F. I've found that Flexicolor Bleach III gets the job done in ten minutes, even so, and I've been giving ten minutes in fixer as well. However, you can neither overbleach nor overfix C-41; both processes should be carried to completion, and no harm can be done by leaving the film in these baths longer (within reason).

Bath A
300 ml Distilled Water
0.5 g Sodium Bisulfite
5.5 g CD-4
4.5 g Sodium Sulfite (anhydrous)

Distilled water to make 500 ml
pH at 75° F should be 6.5 or lower (though I haven't tested mine, having no way to check pH)

Bath B
500 ml Distilled or Filtered Water
45 g Sodium Carbonate (monohydrate) aka washing soda
1 g Potassium Bromide

Water to make 1 liter
pH with original potassium carbonate is listed as 11.8 at 75° F; sodium carbonate should give 11.6 and works just fine

Bath Time

Bath A 3 minutes, return to storage container
Bath B 6 minutes, pour down drain

Times as originally given include 15 seconds pour-out and drain time, i.e. start pouring off when fifteen seconds remain. In practice, like all two-bath systems, Bath A time is grossly non-critical as long as a minimum of three minutes is given; one needs only to ensure enough time for the developer to completely saturate the emulsion. Further, Bath B cannot overdevelop because the developer carried over in the emulsion exhausts in the six minutes given (proved by lack of change in development over a fifteen degree temperature range).
​
 

pentaxuser

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Thanks David and I now understand what bromide does and why in your process it isn't needed thanks to Donald's explanation

petaxuser
 
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Donald Qualls

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Okay, fair warning to those who might be interested to try the Dignan 2-bath NCF-41 I posted above -- PE was pretty sure you couldn't depend on anything about it. See this thread, in which he gives several reasons why it will work differently on different films, different speeds from the same manufacturer, possibly different color balances.

That said, I've had pretty good results in the past, but at that time I was using almost exclusively Fuji Superia Xtra 400 (Fuji and Ferrania were then said to be the films more likely to give good results). As long as I kept the temperature a few degrees above 75F, it worked fine for me. Whether it will work with Kodak films, or with current (often reformulated, perhaps more than once, since Dignan did his work on this) emulsions, is open for question. Also, there was a note that XP2 Super (which I'd expect to be the least critical, since it has only one active emulsion layer) was one of the worst films in terms of results.

I've just finished mixing up my Bath A (Bath B is trivial), so I'll try to get some Superia Xtra 400, already loaded in one of my Kiev 4 cameras, shot in time to test process tomorrow -- that will at least let me know that ferri bleach isn't the source of any later problems, since this is the very same film I had good results with almost fifteen years ago.
 

David Lyga

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I think that this expounded information is beneficial to all.

The C-41 process is, for too many out there, a straitjacket of caveats. A temperature which dares deviate from the normative 100 F is one of the first culprits to get assassinated. And, any modification of formulae strikes most as sheer heresy. But, as the wise and profound Qualls dares to impart, success is achievable without becoming excommunicated in the process.

The purpose of a forum like this is to deliver experiences which might be allowed to deviate from the script. If it were not so permitted, this forum would simply be a rehash of manufacturer's publications. That said, those who at least try to understand such apocryphal writings just might be doomed "to develop" a desire to heed the new way of thinking. Why? Because, experience with such attempts just might have proven itself to become a new and productive component of their technique. What works, works. - David Lyga
 
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Donald Qualls

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Patrick Robert James said:
Donald, years ago PE advised that if you wanted to use a ferricyanide bleach you needed a sulfite bath before and after. Just a heads up.
Click to expand...

Well, sulfite I've got -- bought ten pounds of it on Amazon a couple months ago, just opened it yesterday (and I have some more, old and clumped, in my shed). I find it interesting that Kodak doesn't recommend such a pre- and post-bleach bath for ECN-2 -- that process uses CD-3 instead of CD-4 in the color dev, but the bleach is either the same EDTA base as Flexicolor, or ferricyanide as an alternative (and their publication for that is my source for content of the ferri bleach for C-41). A clearing bath isn't a bad thing, to prevent developer carry-over into the bleach (which I understand to have been the source of warnings I got years ago about Fuji films turning magenta if you use ferricyanide bleach -- it's not Fuji specific, but it's any C-41 stock with developer carry-over), but from my understanding, a water wash (Kodak's pub recommends one minute with constant agitation) is adequate (sulfite after the bleach might be another story -- keep the ferri out of the fixer to avoid potentially bleaching image silver in future bleach bypass runs).

I'm a little concerned about my CD-4, however -- I'm trying to remember if the granules were dark brown/green last time I used it, or if my poor storage has caused it to go off. The Bath A is darker than the color dev in my last Cinestill kit, also. I'll run a leader test before I trust it on any actual film.
 
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Donald Qualls

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Okay, I've hedged my bets. I found everything in stock at Unique Photo, so I went ahead and ordered a set of Flexicolor chemicals -- Developer Replenisher, LORR Developer Starter, Bleach Replenisher, and Fixer and Replenisher. Spent about $95 plus $20 shipping. Separate bleach and fixer lets me do bleach bypass when desired (I quite like shooting XP2 at EI 800 and expecting good shadow detail none the less), as well as being able to use the bleach for things like bleach-redevelop intensification, E-6, etc. I'll probably batch my films in future so I can mix the color dev on a one-shot basis; I surely don't shoot enough color to get replenishment to work correctly. I might even use @David Lyga 's diluted color dev method for XP2, since color rendition isn't an issue (as long as I can get proper density and contrast).

Following up -- my Bath A might be darker because it's got twice the CD-4 in it per volume compared to canonical C-41 color dev -- but I'm still not sure about the condition of my CD-4.
 

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If you use ferricanyde as bleach in a color process you absolutely need to use a "acidic" clearing bath (stop bath+sodium sulfite) after CD and a clearing bath (just sodium sulfite) after the bleach. Any CD in the ferricanyde bleach or any ferricianyde bleach into the fixer produces stains. The clearing baths neutralizes both of them.

Ferricianyde bleach is very, very strong for color processes, I try it with RA4 paper and the bleach is completed in just a couple of seconds. PE had some concerns about dye stability of modern films because it was not tested as a bleach.

PE comments detailed here: (he repeated them many times, so you can probably find them in other threads)
https://www.photrio.com/forum/threa...-vs-ammonium-ferric-edta.145359/#post-1904037

If you use a Jobo with lift I also suggest to open the tank after the the clearings baths and wash it thoughly with tap water. The lift produces too much carryover between baths.
 
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Donald Qualls

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halfaman said:
If you use a Jobo with lift I also suggest to open the tank after the the clearings baths and wash it thoughly with tap water. The lift produces too much carryover between baths.
Click to expand...

No Jobo here, I'm doing hand inversion in Paterson tanks. I've read that continuous agitation isn't advantageous for two-bath developers in any case; the agitation washes the developing agent out of the gelatin before it can do its job.
 

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If you are flirting with an EI of 800 for XP2 and want shadow detail, I suggest you consider giving my method a minute or two more development time. - David Lyga
 
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Donald Qualls

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David Lyga said:
If you are flirting with an EI of 800 and want shadow detail, I suggest you consider giving my method a minute or two more development time. - David Lyga
Click to expand...

I'll keep that in mind, but most of the extra stop I'm talking about for XP2 comes from bleach bypass. Leave the silver image in the film along with the dye cloud image, you get about twice the density, still with hardly any grain (because the dye image masks the silver image grain, and no big contrast boost from the highlights developing more than the shadows.
 

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David Lyga said:
Are you aware, Donald, that one can easily use traditional B&W chemicals to process XP2?
Click to expand...
If I recall correctly and I may not HC110 was used by one member who showed us either his reversed neg scans or prints scans and they looked very good to my eye

pentaxuser
 

David Lyga

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pentaxuser said:
If I recall correctly and I may not HC110 was used by one member who showed us either his reversed neg scans or prints scans and they looked very good to my eye

pentaxuser
Click to expand...
Yes, even though it is chromogenic, it can easily be processed in any B&W developer, and fixed, normally. Its ability to be processed in C-41 facilitates its use for people who wish to let commercial establishments process their films. - David Lyga
 
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Donald Qualls

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I've processed XP2 in Df96 monobath -- the results weren't perfect, but I think they were affected by the monobath fixer component getting tired and/or me not leaving the film in for double time (didn't know in advance that it needed to be treated as a tabular grain). I was led to that by seeing the example page Ilford links for processing XP2 in HC-110 (I'll probably soup it in my replenished Xtol at some point, too).

What I'm after with bleach bypass is to get both the silver and dye cloud image. I've done this in the past with BW400CN, and the result was very good -- but that film wasn't very suitable for wet printing on B&W papers (the mask reduces contrast and makes exposure times very long). XP2 is well known to print well on multigrade, even if processed normally (C-41 all the way). I look forward to printing bleach bypassed XP2 in the near future.
 
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