Pyrocat-HD Sudden Death: Any Updates?

[chuckroast]

Chuckroast has not said he used heated glycol, but I suspect that he did when mixing the HD variant. If all else was followed to the letter on mixing the batch of HD, then that might be his problem. Karl explains it above better than I could. I think that the glycol starts to change color a little when you get it too hot. I have never had HD go bad, and the last batch was 6 years old when I dumped it and switched over to HDC. I didn't dump the HD batch until about a year after I made HDC, simply because I wanted to be sure the newer HDC version was a good switch. I had the same luck with Pyrocat-MC. All my Pyrocat developers were made in glycol.
I don't know what cross contamination could do? I would think it would be hard to cross contaminate, but you never know.

I did heat the glycol but no higher than somewhere around 130-150F, well below the 100C number cited above.

 

[chuckroast]

I think it is possible to check if the Part A of Pyrocat HD is still active using pH paper. The pH of the concentrate should be between 1 and 2.
I have some Pyrocat HD with Part A stored in a 2/3 full glass bottle that is at least 4 years old and still works.
My sodium metabisulfite in a plastic bottle is a few years old and has a slight whiff of sulfur dioxide gas.

I have a pH meter at my disposal. What would the nominal Part A pH be, I wonder, for HD, HDC, etc...

 

[koraks]

I don't see how pH measurement of the part A concentrate would give any conclusive information. If the phenidone (or dimezone etc.) has died, you're not going to notice a significant change in pH, but the developer will be more or less dead anyway.

 

[chuckroast]

I don't see how pH measurement of the part A concentrate would give any conclusive information. If the phenidone (or dimezone etc.) has died, you're not going to notice a significant change in pH, but the developer will be more or less dead anyway.

Yeah, the alkalinity is really established by Part B, right?

 

[koraks]

Yeah, the alkalinity is really established by Part B, right?

Yes,but that's a different matter. The thing is, degradation of the phenidone won't make a meaningful difference in the pH of part A. And oxidation of the pyrocatechol would be very visible, as it would make part A turn the color of coca cola.

 

[Alan Johnson]

If the acidic sodium metabisulfite in the water concentrate Part A is oxidized to sodium sulfate the pH will rise from 1-2 to a more neutral value and the phenidone will no longer be protected and will in turn be oxidized and no longer active. This will occur sooner if the sodium metabisulfite used is not the pure stuff so there is less of it. At low pH there won't be any degradation of the phenidone, that is the reason why the metabisulfite is used in a 2 part formula.
My Part A concentrate in water measures at pH between 1 and 2 using pH paper and at 1+1+100 gives a normal density negative.
I agree it is somewhat debatable that the above would be true if the mix is made mainly in glycol with only a little water but it seems likely.

Mixing Pyrocat HD - Film Developer

Below are mixing directions for various versions of Pyrocat, including DHD, -M, -P, -MC and -PC.

www.pyrocathd.5x4.co.uk

 

[tykos]

Those are the reasons I went with the HDC version over the HD and MC versions I had been using. Plus, I think I read that that is what Sandy King is now using.
As to tykos question about finding the freshest metabisulfite? Where I'm at, I go to the busiest brewing and wine making supply store in my city. Their turnover is pretty darn fast and the sodium metabisulfite is sold in small sealed pouches. I don't know what they use for wine making in Italy, but you should be able to find a source of pretty fresh metabisulfite. Italy has been producing wine for a few years now, I think.

sodium metabisulfite is very well used, but I think they only sell 1kg packs, and in photographic use that can last more than a lifetime...

HDC is surely appealing, apart from buying yet another chemical (I already had metabisulfite to mix hypo-clear), but we'll see.

 

[tykos]

I don’t know if it’s applicable here, but it might be, if you heated it to help absorption.

Heating glycol over about 100 degrees C seems to cause problems (aside from being dangerous if spilled on you). Officially it doesn’t oxidize until 133C but I think it may be that parts of the fluid get that hot even when the whole temp average is not that high. In any case, it breaks down past that point and it’s not the same afterwards. The pH also changes. If you’re heating glycol to help dissolve ingredients, I suggest not to get it over about 80C. You don’t need it hotter than that and it is safer and doesn’t break down. I have not mixed either of these formulas, but do have lots of experience with glycol based developers.

I have to heat my glycol pyrocat because I keep it in a cold room and it forms quite a lot of precipitate. Putting it in some warm (very warm) water for a couple of minutes helps dissolve all the precipitate.
If I remember physics correctly this method won't heat glycol over 100°C, but I'll check and try to heat it even less.

 

[koraks]

Putting it in some warm (very warm) water for a couple of minutes helps dissolve all the precipitate.
If I remember physics correctly this method won't heat glycol over 100°C

This is correct; by heating the glycol in a water bath it cannot become any hotter than the boiling point of the water.

 

[John Wiegerink]

sodium metabisulfite is very well used, but I think they only sell 1kg packs, and in photographic use that can last more than a lifetime...

HDC is surely appealing, apart from buying yet another chemical (I already had metabisulfite to mix hypo-clear), but we'll see.

We have a lot of small home wine makers in this country, so the wine and beer making stores have sod. metabisulfite is smaller quantities. I really like the HDC formula for its ease of mixing and its keeping properties. It also works just like Pyrocat-HD so what's not to like?