C41 RA Bleach Dilution

[Misko78]

I use Tetenal C41RA Bleach, and i'm replenishing but i would love to switch to one shot.
Mixing instructions for 1000ml says 700ml concentrate + 275ml water + 25ml starter and then 5ml per 135-24 film, Bleaching time is 45 seconds.

Does anyone has an idea how to dilute it so i can use it one shot economically. I'm using Jobo ATL 1000 and it is easier for me to have a longer developing time than to sit buy the processor and collect chemistry so time is not an issue, lets say 10-15 minute bleach time, what dilution would give me that time.

 

[Rudeofus]

I am quite sure you can dilute this bleach quite a bit, but you'd have to establish your own bleach times for a range of different film brands. On the other side, bleach lasts forever in terms of working solution shelf life, so it may be much easier and more reliable to just keep the full strength solution over multiple sessions spread out over a year, then dump&replace.

 

[Misko78]

I've managed to reprogram the ATL1000 so that i can replenish and reuse chemicals, i've developed >200 films that way but it is boring as hell, i need to sit by it and then wash the drain hoses and bottles before next batch. Developer is really cheap 10l is ~15€ and i can develop 90 films one shot or ~160 when replenish. Fixer is the same story, but bleach is ~40€ for 5L of concentrate which will make ~7L of working solution and that is enough for 50 films (opposed to 1000 when replenish). But if i can dilute it 1+2 that will be cheap enough to use it one shot. Price per film would be 0,16+0,16+0,26=0,58€ opposed to 0,9+0,9+0,04=0,22€

 

[Rudeofus]

How many films do you usually develop at once? You don't have to replenish after each roll ...

 

[Misko78]

2 or 5, replenish is not a problem, collecting from ATL1000 is. It has two separate hoses one for water and one for chemistry and it is a tedious job to wait for tank dumping moment.

 

[Rudeofus]

If you work yourself through the various MSDSs of C-41 bleach, you will see, that RA type bleaches are more concentrated than those from other product lines. Search for the weakest one you can find an MSDS for, estimate the concentration of Ammonioum Ferric PDTA, and dilute your C-41RA bleach down to that level. This should at least get you into the ballpark.

 

[Misko78]

It seems that it is not possible by simply diluting

Kodak MSDS for Flexicolor RA Bleach:

Ingred Name:WATER
Fraction by Wt: 75-80%
Ingred Name:AMMONIUM FERRIC PROPYLENEDIAMINETETRAACETIC ACID
Fraction by Wt: 5-10%
Ingred Name:AMMONIUM ACETATE
Fraction by Wt: 5-10%
Ingred Name:AMMONIUM BROMIDE
Fraction by Wt: 1-5%
Ingred Name:ACETIC ACID (GLACIAL)
Fraction by Wt: 1-5%

Kodak MSDS for Flexicolor Bleach III:

Ingred Name:WATER
Fraction by Wt: 85-90%
Ingred Name:AMMONIUM FERRIC PROPYLENEDIAMINETETRAACETIC ACID
Fraction by Wt: 1-5%
Ingred Name:ACETIC ACID (SARA III)
Fraction by Wt: 1-5%
Ingred Name:AMMONIUM ACETATE (SARA III)
Fraction by Wt: 1-5%
Ingred Name:AMMONIUM BROMIDE
Fraction by Wt: 1-5%
Ingred Name:AMMONIUM NITRATE (SOLUTION) (SARA III)
Fraction by Wt: 1-5%

 

[chassis]

Interesting. Bleach III time is 6'30". If you are using Bleach RA for 45 seconds, this is approximately an 8x concentration difference, assuming they are used at the same temperature of 100 deg F.

Looking at the ingredient list and fractions above, the active ingredient is roughly 3x more concentrated in the RA bleach. So rough order of magnitude difference between the two solutions is 3x - 8x more concentrated for the Bleach RA. Not sure if this sheds any light or not, but the arithmetic was fun.

 

[Rudeofus]

Well, here is what I found regarding Kodak Bleach III vs. Kodak's C-41RA bleach:

1. PE posted the Bleach III formula just not too long ago (there was a url link here which no longer exists), starting with 30.27 g/l PDTA.
2. There is Kodak's C-41RA bleach formula in US6649331 in Table 3, starting with 113.6 g/l PDTA

This gives a ratio of active bleach agent of about 1 : 3.75 between Bleach III and RA bleach. Since the C-41RA process was aggressively optimized for rapid throughput, whereas the classical C-41 process likely has some margin built in to allow for minor process variations, it's not all that unlikely that bleach speed is more or less proportional to concentration of active agent.