Pyrocat-HD Sudden Death: Any Updates?

John Wiegerink said:

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.

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Alan Johnson said:

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.

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koraks said:

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.

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chuckroast said:

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

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John Wiegerink said:

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.

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relistan said:

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.

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tykos said:

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

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tykos said:

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.

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