View Full Version : C41 and RA4 chemicals and oxygen

26-Aug-2012, 01:16
The developer in both C41 and RA4 processes must be protected from oxygen, of course. But how about bleach, fix and stabilizer? Does contact with air (oxygen) degrade them too? Or is it a waste of money to use Tetenal Protectan with all these chemicals?

26-Aug-2012, 03:14
Fix and bleachfix will go bad, stabilizer likely won't. Use inexpensive wine preservers that do not contain CO2, but instead those that contain argon or nitrogen or a mixture of the two. There are several brands and some can be found for dirt cheap. The cans are disposable, though.

26-Aug-2012, 03:45
RA4 is quite surprisingly stable - the developer really is an activator, the most vulnerable developing agents are dry embedded in the paper, and the blix is well stabilized too. The whole process was designed with low volume desktop roller-transport processors in mind (and based upon experience with similar black and white lith systems for the printing industry) - in my experience it will survive a month or two in such a processor.

26-Aug-2012, 11:23
That said, C41 is far more vulnerable - but it still is stable enough that it does not fail through oxidation in a regular rotary processor schedule (a small kit within two weeks, a large within four to six, or replenish) as long as you store it in the Jobo bottles that go with the processor.

Protectan is best used on concentrate developers, which you plan to use for months or years of single-shot developing. Used chemicals will go stale even if you avoid oxidation, as pollution from the previous runs will interact with the active ingredients, so you'd better use them up within their specified storage life - which generally is given without Protectan or nitrogen protection for manual and small machine processes.

Mark Barendt
26-Aug-2012, 13:13
The developer is what needs protecting, the rest are very stable.

If you read the directions on C41 replenished bleach systems you'll find that "air" agitation is recommended, not nitrogen as recommended for developer. Oxygen is needed to make the bleach work.

RA Blix similarly needs oxygen. In a thread I started on APUG way back when on making RA Blix last longer PE actually recommended shaking up a half full jug of working solution and then letting it sit overnight to re-energize it.