Pyrocat-HD Sudden Death!

Alan9940 · Aug 25, 2019

I posted the following over on LFPF and thought the Pyrocat users here might find it of some interest, too:

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I know this has been discussed a bit in other threads, but thought I'd pass on a warning that...YES, Pyrocat-HD can experience sudden death significantly before you expect it and without warning.

I have a 15 month old batch, mixed in glycol, stored in amber glass bottles with a spurt of Protectan after each use, and kept at about 50-55F in the dark. I mix it myself and have done so for more than 10 years. Before that I bought it from PF and had a batch of that go bad in about the same timeframe. No warning. When I mixed A and B together, it turned the appropriate color. I know some of you have had it go bad and others have it last for years. I'm really starting to not trust it due to this Xtol-like sudden death. If I keep using it, I'm going to mix a small batch in distilled water and toss every 6 months or so.

Anyway, just thought I'd pass this along...
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FWIW...

Born2Late · Aug 25, 2019

This is why I always do a clip test on my developer and fix befor possessing.

Sirius Glass · Aug 25, 2019

Born2Late said:
This is why I always do a clip test on my developer and fix befor possessing.

+1 With ANY developer.

koraks · Aug 25, 2019

Alan9940 said:
I'm going to mix a small batch in distilled water and toss every 6 months or so.

I haven't had the issue you describe, but what you wrote here is my standard practice exactly to prevent this sort of thing. I generally mix pyrocat in 50ml batches. Sounds like a small amount, but a little goes a long way.

Alan9940 · Aug 25, 2019

Born2Late said:
This is why I always do a clip test on my developer and fix befor possessing.

Yep, I was being lazy. Luckily, this morning's negs were simply some testing I was doing for something else.

Alan9940 · Aug 25, 2019

koraks said:
I haven't had the issue you describe, but what you wrote here is my standard practice exactly to prevent this sort of thing. I generally mix pyrocat in 50ml batches. Sounds like a small amount, but a little goes a long way.

Not sue I'll go that small of a quantity, since my typical processing with LF, when using Pyrocat-HD, is minimal agitation using tanks & hangers. My smallest tank is 2L and the larger ones are 5L. The latter is a boat load of chemistry, but Pyrocat makes it fairly economical.

craigclu · Aug 25, 2019

I've had embarrassingly long life with the MC variant. I shouldn't expect it to work at all but I get expected results, even though I wouldn't trust important work to such old mixes.

destroya · Aug 25, 2019

i had the same issue with glycol mixed, and like you switched to distilled water mixing. my guess was contamination from water from cleaning my syringe? i could be wrong, but i switched. i now mix up 200ml worth when needed

Andrew O'Neill · Aug 25, 2019

Never had an issue over the 17 years I've been using Pyrocat-HD. If stored properly, solution A can last up to a year. My current solution A was mixed up in february. I only have about 50ml left and 10ml of that went to develope two 8x10's this morning. The negatives look great. I don't bother with glycol, as it is too expensive up here. Distilled water and stock stored in air tight bottle.

Patrick Robert James · Aug 25, 2019

I never had sudden death, but I had other issues with it so I ended up going back to PMK. I like the PMK negs better for printing too. Life is too short to deal with the grief of an underperforming developer.

juan · Aug 26, 2019

I’ve never had the issue, but a friend did. We traced his problem to his B solution going bad. Sandy was very surprised that it could happen, but I saw the A solution come to life with new B.
To avoid this possibility, I no longer mix a B solution. I compute the amount of carbonate needed in my working solution. I fill my tank with water, add the dry carbonate, max throughly, then the Pyrocat A.

Anon Ymous · Aug 26, 2019

Sorry, but what exactly can go wrong with a carbonate solution? What did it turn to?

koraks · Aug 26, 2019

Beats me, but I've read about it as well once on LFPF. Never experienced anything of the sort with carbonate (Na or K) or hydroxide (again Na or K) solutions, all of which I keep as stocks, sometimes for years, for several purposes. They're as stable as can be. I suppose if you were to bubble them with CO2 for a couple of weeks, you'd get a carbonate solution on its knees, but with regular storage in a bottle (even partially full)? I don't see how that could go wrong.

Ian Grant · Aug 26, 2019

Alan, on another Forum I've mentioned tart it's the Sodium Metabisulphite that protects the Pyrocatechein from oxidising, and that once this breaks down to Sulphite there's no protection, it then deteriorates very rapidly.

It may well be the Metabisulphite isn't fresh enough, that really is the key to longevity, which I discovered by accident as I'd leave Part A (made up in water) unused for moths in the UK while living abroad, and months turned to 3+ years and it was still fine in a partially filled bottle, I was using a little on every trip home.

Sodium Bisulphite is a lower grade mixture of Metabisulphite and Bisulphite and offers less protection than Metabisulphite.

Ian

Alan9940 · Aug 26, 2019

Ian Grant said:
Alan, on another Forum I've mentioned tart it's the Sodium Metabisulphite that protects the Pyrocatechein from oxidising, and that once this breaks down to Sulphite there's no protection, it then deteriorates very rapidly.

It may well be the Metabisulphite isn't fresh enough, that really is the key to longevity, which I discovered by accident as I'd leave Part A (made up in water) unused for moths in the UK while living abroad, and months turned to 3+ years and it was still fine in a partially filled bottle, I was using a little on every trip home.

Sodium Bisulphite is a lower grade mixture of Metabisulphite and Bisulphite and offers less protection than Metabisulphite.

Ian

Ian, it could very well be my Metabisulphite is causing early death because what I have is years old. Any idea how long this chemical should last under reasonable storage conditions?

Andrew O'Neill · Aug 26, 2019

Patrick Robert James said:
I never had sudden death, but I had other issues with it so I ended up going back to PMK. I like the PMK negs better for printing too. Life is too short to deal with the grief of an underperforming developer.

I worked with PMK for about a year and it just didn't do it for me. HP5 sucked in it. Even in Rollo. Went back to Pyrocat-HD. To each his own, eh?

Alan Johnson · Aug 26, 2019

Ian Grant said:
Alan, on another Forum I've mentioned tart it's the Sodium Metabisulphite that protects the Pyrocatechein from oxidising, and that once this breaks down to Sulphite there's no protection, it then deteriorates very rapidly.

It may well be the Metabisulphite isn't fresh enough, that really is the key to longevity, which I discovered by accident as I'd leave Part A (made up in water) unused for moths in the UK while living abroad, and months turned to 3+ years and it was still fine in a partially filled bottle, I was using a little on every trip home.

Ian

Also there is much less protective metabisulfite in Pyrocat (10g/L) than sulfite in Microphen (ID68) 85g/L

Ian Grant · Aug 26, 2019

Alan9940 said:
Ian, it could very well be my Metabisulphite is causing early death because what I have is years old. Any idea how long this chemical should last under reasonable storage conditions?

Hard to put a time on it, it's deteriorating at a slow rate all the time, 3-5 years though it's cheap anyway. You could double or even treble the Metabisulphite with no effects on the final working solution but extending storage,

Alan Johnson said:
Also there is much less protective metabisulfite in Pyrocat (10g/L) than sulfite in Microphen (ID68) 85g/L

There's Metabisulphite in Microphen in Part A to protect the developing agents during storage it breaks down to Sulphite when the developer is mixed. Sulphite has weak anti oxidant properties but not enough to protect Pyrocatchin for long ina working solution.

Ian

Alan9940 · Aug 26, 2019

Ian Grant said:
Hard to put a time on it, it's deteriorating at a slow rate all the time, 3-5 years though it's cheap anyway. You could double or even treble the Metabisulphite with no effects on the final working solution but extending storage,

Thanks, Ian, learn something new all the time! I'm thinking I'll use up what I have and mix very small quantities to keep it as fresh as possible.

Alan Johnson · Aug 26, 2019

Ian Grant said:
Sulphite has weak anti oxidant properties but not enough to protect Pyrocatchin for long ina working solution.

Ian

It is bisulfite which is stable at the pH of the Part A solution .It would probably oxidize to the stable form sulfate at this pH.but as far as I can see from Mees and James 3rd ed p289 available details are only in old papers and not readily accessible.

john_s · Aug 26, 2019

Ian Grant said:
....... You could double or even treble the Metabisulphite with no effects on the final working solution but extending storage.........

Ian

Interesting idea. Would the extra acid in part A require a bit more carbonate in part B to adjust, or would the effect be insignificant? (I'm not a chemist!)

Ian Grant · Aug 27, 2019

Alan Johnson said:
It is bisulfite which is stable at the pH of the Part A solution .It would probably oxidize to the stable form sulfate at this pH.but as far as I can see from Mees and James 3rd ed p289 available details are only in old papers and not readily accessible.

There's no Bisulphite in Part A, and Metabisulphite (and Bisulphite) form Sulphite and water when Part B is added. Pure AR grade Sodium or Potassium Bisulphte is quite unstable and has a short shelf life and that's before it's in solution, what's sold as Sodium Bisulphte for commercial use is a mixture of Metabisulphite and Bisulphite:

JT BAker MSDS for Sodium Bisulphite
Sodium Bisulphite 7631-90-5 58 - 99%
Sodium Metabisulphite 7681-57-4 1 - 42%

For Sodium Metabisulphite it's >98%

Sodium Bisulphite is made by bubbling so2 through Sodium Hydroxide or Sodium Bicarbonate solution, Sodium Metabisulphite is a step further bubbling SO2 through Sodium Bisulphite solution. This helps explain why commercial Bisulphite is stable and contains Metabisulphite and it's the free SO2 from the presence oft the Metabisulphite that keeps the Bisulphite stable.

It's very obvious that Bisulphite contains less free Sulphur Dioxide than Metabisulphite, the had different CAS and E numbers and have differing uses in industry. Kodk's Sodium Bislphite is a higher proprtion of Metabisulphite approx 80% and 20% Bisulphite it's not a high enough proportion to be calle etabisulphite.

john_s said:
Interesting idea. Would the extra acid in part A require a bit more carbonate in part B to adjust, or would the effect be insignificant? (I'm not a chemist!)

At 10gms per litre and mixed 1+1 to 100 that's 0.1g in a litre of working developer compared to 7.5g of Potassium Carbonate so quite insignificant, double the amount will be barely detectable, I have used 15g Metabisulphite in Part A and there's no change at all in use.

Ian

Alan Johnson · Aug 27, 2019

https://www.researchgate.net/public...n_beer_Reviewing_regulation_analysis_and_role
See Fig 1, in presence of water HSO3- is the predominant ion present from pH 2 to pH7.
If made up in glycol, with commercial metabisulfite , from what you say I believe that may effectively have a small content of H20 from some of the bisulfite dissociating to metabisulfie + H20.
In both cases there will be bisufite ion present but from what you say it will be very much less in glycol but not zero, which explains why it is long lasting.
Maybe the glycol mix will last longer if made with pure metabisulfite and not commercial grade.

Ian Grant · Aug 27, 2019

You have to add some water to dissolve the Metabisulphite as it won't dissolve in Glycol, The small amount of water doesn't affect keeping as my double strength Part A in Glycol is 9+ years old and there's no oxidation..

With a shelf life of 3+ years made up in water I've not made up Pyrocat HD in Glycol again as it greatly increases the cost with no benefits unless you really need a very long shelf life, I use up my Pyrocat HD much faster than 3 years, normally in a few months.

Ian

Raghu Kuvempunagar · Aug 27, 2019

Ian Grant said:
You have to add some water to dissolve the Metabisulphite as it won't dissolve in Glycol

There's a variant of Pyrocat called Pyrocat HDC which could be of interest to those who want a long lasting variant of Pyrocat. It doesn't use metabisulphite+bromide and hence completely avoids water. I believe ascorbic acid which dissolves nicely in warm glycol provides the necessary acidic environment to prevent the oxidation of catechol. Developing time and results are supposed to be very similar to HD.

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