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Pyrocat HDC in Propylene Glycol - keeping qualities?

BHuij

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About a year ago, I mixed up 500ml of Part A and 500ml of Part B using the following recipes:

Part A:
400ml Propylene Glycol (gently heated) to around 40°C
25g Pyrocatechin
1.25g Phenidone
2g Ascorbic Acid
Top off to total volume of 500ml with more PG

Part B:
400g distilled water
375g Potassium Carbonate
Top off to total volume of 500ml with more distilled water

They have been sitting in nearly full PET bottles at room temp in the dark ever since.

I know for sure that they still develop film since I used some 1:1:100 a week or two ago to develop a sheet of HP5+.

What I don't know is whether this year-old stuff is going to produce the same results that it would have produced when it was freshly mixed up. The whole reason I chose glycol instead of water-based recipes for the actual developing agents was so I could mix it once and forget about shelf death for... hopefully years. Am I in good shape here, or does Pyrocat HDC in glycol still have a shelf life for the Part A concentrate I need to keep track of?
 

GregY

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I use Pyrocat HD in glycol ....it's always lasted a year or more for me with no surprises & i buy it from PF and don't decant.
 
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BHuij

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My understanding is that in vitamin C developers, the usual methods of developing agents losing their effectiveness are heat, oxidation, and the Fenton reaction. I suppose despite the inclusion of phenidone and ascorbic acid, Pyrocat HDC might not technically count as a vitamin C developer in the purest sense of the term. But in any case it seems like heat, oxidation, and the Fenton reaction are all essentially nonissues when there's zero water in the Part A concentrate. If that's correct, then a full bottle of Part A should last virtually indefinitely, a la Rodinal or HC-110 (both of which I have used and gotten perfect results with expected densities with 10+ year old concentrate).

But I'm not a chemist, and "in theory, by my layman's understanding" is vague enough that I figured I'd ask the experts here, specifically hoping for real world experience. If someone told me their Pyrocat HDC Part A concentrate in glycol went bad after a year or 2 years or 5 years, that would be relevant.
 

Ian Grant

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GregY said:
I use Pyrocat HD in glycol ....it's always lasted a year or more for me with no surprises & i buy it from PF and don't decant.
Click to expand...

Is that all . . . . . . . . .

I mix Pyrocat HD Part A with water, and it lasts up to 4 years even in a partially full bottle, As long as your Sodium Metabisulphite is reasonably fresh.

In Glycol Part A lasts way longer, I think I'm up to 15 years, I did mix at double strength. But the extra cost of the Glycol is a waste when the dev lasts so well just mixed in water.

Ian
 

Alan Johnson

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There have been reported failures but IMO they may be related to porous type plastic (not PET) or absorption of water from the air, unlikely in the situation of post 1.

AI Overview
Yes, propylene glycol (PG) is
highly hygroscopic, meaning it readily attracts and holds water molecules from the surrounding air, acting as a humectant in many products like cosmetics, foods, and pharmaceuticals, but it must be stored in sealed containers to prevent moisture absorption.
 

Ian Grant

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Here in the UK a developer called Prescysol was sold by Peter Hogan, it had a short shelf life. Its instructions were word for word exact copy of Sandy King's original Pyrocat HD. By original, I mean Part B was Sodium Carbonate, so typically used 1 +3 to 100, then someone suggested Sandy King use Potassium Carbonate as it's way more soluble.

Hogan used Low Density plastic bottle, and it rarely lasted more than a few months.

Ian
 

pentaxuser

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Ian Grant said:
Is that all . . . . . . . . .

I mix Pyrocat HD Part A with water, and it lasts up to 4 years even in a partially full bottle, As long as your Sodium Metabisulphite is reasonably fresh.


Ian
Click to expand...
Ian there's seems to be a difference between what you use in Part A and what the OP uses He makes no mention of Sodium Metabisulphite

pentaxuser
 

GregY

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Ian the 50 litre kits never last me that long....in 4 yrs i'll go through at least 3 of them. It's my standard developer.
 
Last edited:

John Wiegerink

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BHuij said:
Pyrocat HD vs HDC. Somewhat different recipes, though by all accounts virtually identical results.
Click to expand...
Yes, I transitioned over from Pyrocat-HD to Pyrocat-HDC and never even felt a speed bump. I notice at first that HDC seemed to built a touch more density, but it might have been just my processing or slight agitation difference the first time I used it with HP5+. I have used HDC, HD and the MC versions of Pyrocat and they are all first rate film developers. If you are very happy with your results from Pyrocat-HD I would continues to used it until it were gone or has gone flat before I would switch the the HDC version. No sense dumping a perfectly good developer for really no gain.
 

mpirie

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pentaxuser said:
Ian there's seems to be a difference between what you use in Part A and what the OP uses He makes no mention of Sodium Metabisulphite

pentaxuser
Click to expand...

I think that's down to the OP referring to HDC (with Ascorbic Acid) and Ian referring to HD (with metabisulphite).

Mike
 

pentaxuser

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mpirie said:
I think that's down to the OP referring to HDC (with Ascorbic Acid) and Ian referring to HD (with metabisulphite).

Mike
Click to expand...

Thanks. I am sure both of you who have replied are right about the "why" but it was just about whether the use of Sodium metabisulphite in HD has any relevance to the OP's concern about the longevity of HDC with ascorbic acid

pentaxuser
 

Milpool

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I’m not sure if this will completely address your question but the ascorbic acid in the HDC formula plays the roles the metabisulfite plays in the regular HD formula (antioxidant and weak acid). While the use of metabisulfite in HD isn’t directly relevant to HDC, OP seems to be wondering about the long term stability of ascorbic acid in that role. In theory it should last for a very long time but this will always depend on the purity of the other compounds. Regarding runaway oxidation of ascorbate / Fenton, the most common sources of iron / copper impurities are water and sulfite (most relevant in developers containing a lot of sulfite), neither of which are used in glycol HDC part A.


pentaxuser said:
Thanks. I am sure both of you who have replied are right about the "why" but it was just about whether the use of Sodium metabisulphite in HD has any relevance to the OP's concern about the longevity of HDC with ascorbic acid

pentaxuser
Click to expand...
 

Ian Grant

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BHuij said:
Pyrocat HD vs HDC. Somewhat different recipes, though by all accounts virtually identical results.
Click to expand...
pentaxuser said:
Ian there's seems to be a difference between what you use in Part A and what the OP uses He makes no mention of Sodium Metabisulphite

pentaxuser
Click to expand...

Yes a slight variation, Sodium Metabisulphite won't dissolve in Glycol, so you need you mix it with around 50ml of water to mix Pyrocat HD in Glycol. If you switch to Ascorbic acid as the anti-oxidant, no water is needed.

My point is Propylene Glycol adds quite a bit of extra cost, more than double, to mixing Part A, and gives me no extra benefits. I've always found HD Part A lasts 4 years in water. Normally, I would finish a batch in under that time, but while living abroad I also had Pyrocat HD here in the UK which was only used on trips home, and later the reverse, developer sat in our apartment abroad, which I used on Summer visits.

Ian
 

chuckroast

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It will easily keep that long. I have HDC over a year old that is quite happy.

I did experience early HD morbidity, even in glycol , well before a year, so I never trusted it again.
 

Ian Grant

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chuckroast said:
It will easily keep that long. I have HDC over a year old that is quite happy.

I did experience early HD morbidity, even in glycol , well before a year, so I never trusted it again.
Click to expand...

If that's the case, then the storage bottles were not High Density Plastic or Glass, or the Sodium Metabisulphite wasn't fresh enough.

Ascorbic Acid also has a short shelf life, so needs to be reasonably fresh. You can tell when Metabisulphite has deteriorated, there is no longer a string acidic SO2 smell, but with Ascorbic Acid you have no indicayion of its veracity.

Ian
 

chuckroast

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The bottles were glass but the Metabisulphite could have been the issue, I guess.

Any idea what the keeping time of ascorbic acid might be?
 
Last edited:

tcolgate

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I use HDC mixed in glycol. I mix 200ml at a time and it lives it's life in partially filled glass bottles. I've not noticed any change in behaviour over 6 months to a year for any batch.
 

Gim

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I just opened my last glass bottle of Pyrocat-HD in glycol mixed 10/5/15 per Sandy's instructions on APUG 9/22/06. Stored in larger glass bottles in cardboard box and broke down to smaller bottles for use. Smaller bottles can set half full for long periods with no problem. I made two liters at a time and have had no problems.
 

John Wiegerink

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What more could you ask for? A superb developer with a very long shelf life. Oh, and it's not to picky as to which film gets thrown into it either.
 
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