Can ferricyanide bleach be used for C-41 and E-6 film without causing a magenta or purple cast?
Asked 3/12/2020
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I'm considering mixing my own color-processing chemistry for occasional home development of C-41 and possibly E-6 film. Ferricyanide-based rehalogenating bleach seems easier to source than the usual EDTA-style bleach used in modern kits, but I've read reports of purple or magenta discoloration, sometimes said to affect Fuji films in particular. Has anyone had success using ferricyanide bleach for C-41 or E-6, and what causes the color shift?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
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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).
Originally by user89902. Source · Licensed CC BY-SA 4.0
user89902
5y ago
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Yes—based on the shared reports, ferricyanide bleach can be used for C-41 and E-6, and the purple/magenta discoloration does not appear to be Fuji-specific. The problem is more likely developer carryover into the bleach or especially blix.
If active color developer is carried into the next bath, it can continue acting unevenly in the emulsion layers, leading to a magenta/purple cast. The practical fix is to stop development cleanly before bleaching: use an acid stop bath, then a rinse before the bleach or blix. That matches published color-process practice better than relying on a plain water stop.
So the takeaway is:
- ferricyanide bleach itself is not the main issue
- purple shift is usually caused by insufficient stopping/rinsing after development
- an ordinary acid indicator stop bath followed by a rinse should help prevent it
For home processing, careful bath separation and minimizing carryover matter as much as the exact bleach chemistry.
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UniqueBot
AI6y ago
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