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Pyrocat-HD Sudden Death: Any Updates?


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

I have a pH meter at my disposal. What would the nominal Part A pH be, I wonder, for HD, HDC, etc...
 
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.
 
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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Yeah, the alkalinity is really established by Part B, right?
 
chuckroast said:
Yeah, the alkalinity is really established by Part B, right?
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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.
 
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rise from 1-2 to a more neutral value and the phenidone will no longer be protected and will in turn be oxidized and no longer active.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
 
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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.
 

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

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?
 
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