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I've got limited experience developing color films -- I've done a few rolls of C-41 using a two-bath color developer from a formula I found online, and Kodak bleach-fix and stabilizer, several years ago. I've also done reversal processing of black & white films, to produce positive images (effecively grayscale slides, though I never mounted the frames).

I'm returning to film photography now after several years away, and the availability of bulk chemistry seems to have dropped off, likely related to the closure of most on-the-spot processing labs (fewer local labs, fewer develop/scan/print machines running, fewer sources for chemistry). I'm less than enthused about the cost of commercial C-41 and E-6 kits for a few rolls at a time, and still less so about the shelf life of partially used bottles of those chemicals.

Mixing my own developers isn't difficult, and the component chemicals appear to be still available (and in powder form, they will keep a long time). Stop baths are overrated, and for C-41 in the past I've used a water rinse. Of course, E-6 requires a first developer, and commercial kits use a self-fogging color developer, but ordinary black & white developers can be used for first dev and light exposure worked fine to exposed the undeveloped halide back when I first did the (IIRC) fourteen steps of E-4, in the mid-1970s.

My main concern is the bleach. Modern color processes use an EDTA based rehalogenating bleach; in home kits, this is often mixed with the fixer to reduce the bath count (this is unlike B&W reversal, which requires bleaching the developed silver without removing the unexposed halide). This chemistry is much more difficult to source than the CD-3 or CD-4 color developing agent. I've recently learned that some people have been using a ferricyanide based rehalogenating bleach, similar to Farmer's Reducer or the bleach baths used for some print toning processes.

I recall, when I first approached color processing around fifteen years ago, reading that specifically Fuji color films would produce a strong purple if exposed to ferricyanide, and never pursued it further because at that time it was fairly easy to obtain gallon jugs of bleach or blix for auto processor machines. Since this has changed, I need to find out: has anyone used a ferricyanide bleach to process Fuji C-41 or especially E-6 films, and if so, was there a purple shift?

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Recent reading on Photrio, as well as conversations with YouTube users who've used this bleach method for C-41 and E-6, has led me to understand that the purple discoloration that's been reported from use of ferricyanide bleach is not brand specific, but in fact comes from carrying over active developer into the bleach bath or especially blix (where, due to layer order, the magenta-forming layer is fogged and partly developed to a greater extent than the other color layers).

The solution appears to be use of an acid stop bath, followed by a rinse step, as recommended in the C-41 and ECN-2 process instructions as published by Kodak and Fuji (for their equivalents). Reports suggest that a common indicator stop, as often used for B&W and print processing, is entirely acceptable (the indicator, bromocresol purple, hasn't been reported to cause problems, as far as I'm aware).

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