C-41 bleach: replenisher vs. regenerator?

[srs5694]

Because the bleach is the most expensive part of the C-41 process, I've decided to start replenishing mine, as per the table in a PDF from Kodak's Web site (69ml per 36-exposure 35mm roll). Unfortunately, I bought the wrong stuff when I placed my order -- I mistakenly bought bleach regenerator rather than bleach replenisher. Is the regenerator any good to me at all? Could I convert it into replenisher or first-time-use bleach by adding something? I'm using a manual small tank, not any sort of processor, if it makes any difference. Thanks for any advice.

 

[Photo Engineer]

No, it is not, unless you have bleach!

Bleach is regenerated by two processes, oxidation and replenishment. The 'regenrerator' contains the chemicals used up by bleaching (NaBr - sodium bromide) and an oxidant that oxidizes the ferrous EDTA (or current subsitute).

You could replenish by using air and then NaBr.

PE

 

[srs5694]

Sorry, PE, I'm afraid your answer just leaves me with more questions. I've got bleach and I've got bleach regenerator, but I'd meant to buy bleach replenisher. My understanding from the Kodak PDF was that I'd do a roll of film, replace 69ml of bleach with bleach replenisher, do another roll, and so on ad infinitum. Your response makes it sound as if both replenisher and regenerator are necessary to do something like this.

 

[Photo Engineer]

Sorry, PE, I'm afraid your answer just leaves me with more questions. I've got bleach and I've got bleach regenerator, but I'd meant to buy bleach replenisher. My understanding from the Kodak PDF was that I'd do a roll of film, replace 69ml of bleach with bleach replenisher, do another roll, and so on ad infinitum. Your response makes it sound as if both replenisher and regenerator are necessary to do something like this.

Lets try this then....

If the regenerator is the same color as the bleach, then it can be used, in part, as a bleach, but if it is colorless, or nearly so, then it is just the oxidant to regenerate (oxidize) the bleach plus some sodium or ammonium bromide.

When I worked on C41, the regenerator was a colorless solution that was a concentrated oxidant intended to just oxidize spent bleach back to the ferric form and add some sodium or ammonium bromide. But, if it is colored the same as the bleach, then it containes some amount of ferric ion and is partially usable as a bleach in its own right.

Did this clarify things?

PE

 

[srs5694]

The regenerator has a color that's similar to that of the bleach; it's definitely not clear. Basically I'm just looking for a way to cut the costs of the bleach step. Using Kodak's bleach without replenishment as recommended in Kodak's instructions (two-shot) costs about $1 per roll of film just for the bleach step. Using Kodak's bleach replenisher should cut that cost substantially, except that I bought the wrong product. Therefore, I simply want to know what the difference is between Kodak's bleach replenisher and Kodak's bleach regenerator (as a practical matter; anything more than very basic chemical descriptions are likely to go over my head), and whether the regenerator is useful to me. The Kodak publications I've perused have been unenlightening; they all seem to assume that the reader already knows what these two products are used for.

 

[Photo Engineer]

Well, from your description, I'm confused then, as the regenerator now appears to be different than the old regenerator.

I can say this, that the regenerator and replensisher must match the bleach it is used with. The current bleach is C41 bleach III. It uses a new complex of iron instead of the previous ferric edta, so if the colors are the same, and the same intensity, I would say it can be used. If the regenerator is lighter in color but the same hue, then it can be used, but will need a longer time.

If the color is different than the bleach then they cannot be mixed.

Now, how to test it. Take a piece of B&W film and develop it to completion. Wash it and then dip it into the regenerator and time the amount of time it takes to clear. This is at room temp. Then fix the B&W film and make sure it clears completely.

If the bleaching takes place in under 3 minutes, then you can use it as a bleach for your color films. If it takes more than 3 minutes then use that extra time as a % over 3 mins for increasing the bleach time of color film at 100F. If the film does not clear at all, then it is unsuitable. If the film is not suitably clear after the fix, then the time in the bleach or the bleach activity was too low for good results with color film. You may have to use more time.

If no time increment works with the B&W film, then it is useless for a color bleach, but things can be done to make it work. For example, you could probably mix it with regular bleach 1:1 to extend the volume of good bleach. You would have to again test the bleach times to insure good bleaching.

Does this help?

PE

 

[srs5694]

Does this help?

A bit. I was hoping it could be used in place of bleach replenisher to help keep costs down.

 

[Photo Engineer]

Read what Kodak says about replenishing C41 bleach. If the regenerator is a bleach itself and is fast enough, then it could probably be used as a bleach or as a bleach replensiher, depending on your thoughts.

In any case, if it is a bleach, you have not lost any money on it.

PE