Reusing C-41 Bleach

There are control data plots on the Kodak web page that show what happens when the bleach goes bad. Basically you will find colors become desaturated, grain goes up and Dmin goes up.

PE

Thanks PE! Any thoughts on the Kodak Regenerator and how many times one might be able to use it, offhand? Finding some way to test the pH - would that be helpful in diagnosing if it's still good? I read the docs on the regenerator, but they don't mention a capacity or lifetime for the bleach. They basically show a closed-loop system though, schematically, where the overflow bleach is regenerated and becomes replenisher. The biggest thing they talked about was evaporation, which is probably a non-issue in my case.

Most appreciated,

-Ed

EdSawyer said:

Thanks PE! Any thoughts on the Kodak Regenerator and how many times one might be able to use it, offhand? Finding some way to test the pH - would that be helpful in diagnosing if it's still good? I read the docs on the regenerator, but they don't mention a capacity or lifetime for the bleach. They basically show a closed-loop system though, schematically, where the overflow bleach is regenerated and becomes replenisher. The biggest thing they talked about was evaporation, which is probably a non-issue in my case.

Most appreciated,

-Ed

Click to expand...

Interesting, I wonder how pumping air into bleach also effects this. I have E-6 and C-41 bleach in buckets (with lids) for my Phototherm. Every night for an hour, a little air pump (from a fish tank) pumps air into the bleach. I have not done enough processing of color to exhaust the bleach it's self (5L), so not sure it's even an issue yet...

The bleach is reduced by oxidizing Silver metal in film. This is repaired to an extent by bubbling air through the bleach. However, the pH changes and some ingredients are used up such as Sulfite, Halide, Ammonia, and ETDA (or NTA depending on bleach type).

Therefore, the exhausted chemicals must be replenished, the Iron must be oxidized and the pH must be repaired. The amount depends on how you handle your particular process. Kodak gives guidelines and I suggest that you go by them. They will work with a recirculation system or a batch operation if you adjust things correctly.

PE