Pyrocat-HD developer- how long does working solution last?

Well I had my first Pyrocat-HD developer failure last night. I had been doing 4 sheets of 4x5, 300ml with 1:1:100 dilution in my Jobo tank for 15 minutes with a 5 minute prewash. The only thing I can think of that is different about this batch is that I mixed the developer the night before and kept in a half-full bottle. The developer was a very dark color different then the clear color it is when I mix it immediately before use. I suspect that was my problem.

But for the record does the Pyrocat-HD working solution not last long? Would this cause total developer failure (i.e. completely blank sheets). I did not see this important piece of information mentioned anywhere except in about page 7 of a long forum thread.

Any Pyrocatechin developer has a short life once mixed & diluted, that can be anthing from 5-10 minutes to about half an hour.

No developer should really be diluted & left overnight but a few may still be useable but not Pyrocat.

Ian

Agreed. Pyrocatechin and pyrogallol developers degrade very fast. I would think an hour is too long. I mix mine up within a couple of minutes of starting development.

I had a similar failure early on with pyrocat, but mine was instead from making up 1:10 "stock" solutions for the A and B parts to ease mixing up the final dilution. This resulted in vastly decreased shelf life w.r.t. the proper stock solutions. After that, I switched to using Pyrocat-HD in glycol as my stock solution, along with measuring pipettes suitable for the volumes involved.

Also be sure to never cross-contaminate the A part with the B part. Apparently it doesn't take but a tiny contamination with the B part to cause the A to rapidly deteriorate. For me, this means that the pipettes used to measure each part are clearly labeled and stored in different (also labeled) ziplocs when not in use.

Thanks good to know. I have also been using one syringe to measure both solutions but I've been pretty careful about rinsing it out between parts. Might be safer to start over from scratch at this point I think.

To the best of my recollection, the instructions that come with the Pyrocat-HD I get (Photog. Formulary) say the working solution does not last long and to use it immediately. My working method is to put in the water for my pre-wash, mix the developer, dump out the pre-wash (I do 3 minutes) and pour in the developer.

I've had up to 1 hour transpire between mixing and use (two batches of film back-to-back) with Pyrocat HD without failure. I let a batch go for four hours once, and it was really bad- it made it look like I underexposed by three stops.

My standard method for developing 5X7" film is to place the film in open end PVC tubes, and then put them in a Beseler 11X14" print drum filled with developer to cover the tubes. This requires almost three gallons of developer which is way more than needed to develop six sheets of film, which is determined by how many tubes I can place in the drum. I develop with minimal agitation, which means that the developer is not getting much movement or exposure to air. With this method I will re-use the developer for a total of three batches of six sheets each, with the last batch out of the developer within less than 2 hours of when it is first mixed.

I don't normally recommend reuse of Pyrocat-HD, but in a situation like the above it is perfectly safe to do so, because of the great excess of developer being used over what would be the minimum needed, and because of the reduced type of agitation, and the fact that little oxidation can take place.

Sandy King

TheFlyingCamera said:

I've had up to 1 hour transpire between mixing and use (two batches of film back-to-back) with Pyrocat HD without failure. I let a batch go for four hours once, and it was really bad- it made it look like I underexposed by three stops.

Click to expand...

I'm mixing no more than 1 liter of working strength (1:1:100) and using 500cc's at a time in my Jobo Expert drum, so I don't have that excess, and the 2nd batch of 500ccs is sitting in a half-empty bottle. Thus the 1 hour maximum time from mix to use.

I recon that you could add the "B" part at the very last minute, or just as you're about to pour it into the drum/lift, or some variation of this to ensure that the A and B parts are kept separated until the actual developing stage.
Even though the A part probably will start oxidize some when mixed with water, it's the mixing with the B part which both makes the developer active and kills it. (Sounds like some drug. )

//Björn

Is there a quick and easy way to tell if Part "B" has gone bad?

As B is just an alkali it is not likely to go bad. But a test of its pH would tell.