Another Pyrocat question?

John Wiegerink · Oct 17, 2016

I'm almost out of my last batch of Pyrocat-MC and my order of pyrocatechin is due here today. I mix mine with glycol for its keeping properties. Here's my question..................Pyrocat-MC calls for Ascorbic Acid. My Ascorbic Acid is nearly 3 1/2 yrs old. It's in a baggie and the baggie is in a plastic jar with screw lid, but is it fresh enough to use for the new batch and how do I tell if it is fresh? Pyrocat-HD calls for Sodium Metabisulfite instead of Ascorbic Acid. Can I just use the same amount of Sodium Metabisulfite in the Pyrocat-MC as a substitute for Ascorbic Acid?

Andrew O'Neill · Oct 17, 2016

I have a container of Ascorbic Acid that has been with me since 1998. It still is a white powdery substance and still works fine. Sorry, cannot answer your second question in regards to Sodium Metabisulfite. Ask Sandy King.

John Wiegerink · Oct 17, 2016

Well, after reading Andrew's comment I'll just use my "powdery white" Ascorbic Acid. still, I wonder why Sodium Metabisulfite in one and Ascorbic Acid in the other?

john_s · Oct 17, 2016

I use pure ascorbic acid as a dietary supplement. If it's dry it keeps well. If the jar is repeatedly opened in a humid environment over weeks, there is some discoloration. I assume that is deterioration. So I would conclude that if yours is still white, it's good.

John Wiegerink · Oct 17, 2016

john_s said:
I use pure ascorbic acid as a dietary supplement. If it's dry it keeps well. If the jar is repeatedly opened in a humid environment over weeks, there is some discoloration. I assume that is deterioration. So I would conclude that if yours is still white, it's good.

Well, that's what I'll assume too. I guess I'll find out................

ritternathan · Oct 17, 2016

Yes but you want to use the Ascorbic at 4g/L while the Sodium Metabisulfite should be at 10g/L.

John Wiegerink · Oct 17, 2016

ritternathan said:
Yes but you want to use the Ascorbic at 4g/L while the Sodium Metabisulfite should be at 10g/L.

Yes, I knew that, but just wonder if there was a reason the HD version use Sodium Metabisulfite and MC version used Ascorbic Acid. Come to think of it I do know why. I remember reading some posts many years ago about Pyrocat developers and it seems that Sandy King was to real developer of the HD version and I seem to remember that Patrick Gainer (boy I miss him) had his hand in making up the MC version. Pat always pushed Vit. C "Ascorbic Acid" in many of his concoctions. I think it's also why the MC version has to be made in glycol since it lack Sodium Metabisulfite as a preservative.

Gerald C Koch · Oct 17, 2016

John Wiegerink said:
Yes, I knew that, but just wonder if there was a reason the HD version use Sodium Metabisulfite and MC version used Ascorbic Acid. Come to think of it I do know why. I remember reading some posts many years ago about Pyrocat developers and it seems that Sandy King was to real developer of the HD version and I seem to remember that Patrick Gainer (boy I miss him) had his hand in making up the MC version. Pat always pushed Vit. C "Ascorbic Acid" in many of his concoctions. I think it's also why the MC version has to be made in glycol since it lack Sodium Metabisulfite as a preservative.

Please reread post #3. Michael explains why the HD and MC versions are different. You can't mix and match ingredients between them.

John Wiegerink · Oct 18, 2016

Gerald C Koch said:
Please reread post #3. Michael explains why the HD and MC versions are different. You can't mix and match ingredients between them.

Jerry,
I read it and re-read it, but still don't get why. Of course I only took high school chemistry and that was 50yrs ago so that might explain why I'm puzzled.

Pyrocat-HD (solution A) Distilled water 1000, Sodium Metabisulfite 10g, Pyrocatechin 50g, Phenidone 2g, Potassium Bromide 1g

Pyrocat-MC (solution A) Propylene Glycol 1000ml, Pyrocatechin 50g, Metol 2.5g, Ascorbic Acid 4g.

Now, I can understand not switching the Sodium Metabisulfite out of HD and replacing it with Ascorbic Acid since being mixed with water instead of Propylene Glycol it would need the Sodium Metabisulfite for a stable preservative. The thing I don't see or understand is why one can't mix MC version by using distilled water instead of Glycol, removing the 4g Ascorbic Acid and replacing it with 10g of Sodium Metabisulfite + 1g of Potassium Bromide. I might just mix a scaled down version of the MC with Sodium Metabisulfite+Potassium Bromide in place of Ascorbic Acid and see if it works. All it would actually be is just swapping Phenidone for Metol or Metol for Phenidone whichever way you want to look at it.

ritternathan · Oct 18, 2016

This is from the mixing instructions at http://www.pyrocat-hd.com/html/mixing.html

E. Pyrocat-M (Solution A mixed in water)
Stock A
Distilled Water at 120F 750 ml
Metol 2.5g
Sodium Metabisulfite 10g
Pyrocatechin 50g
Water to 1000ml

Notes:

Mix the chemicals in the order given and stir until dissolved before adding the next chemical.
The use of the potassium bromide restrainer used in Pyrocat-HD is not needed with Pyrocat-P and Pyrocat-M because of the lower pH threshold of metol and p-aminophenol than phenidone.

John Wiegerink · Oct 18, 2016

ritternathan said:
This is from the mixing instructions at http://www.pyrocat-hd.com/html/mixing.html

E. Pyrocat-M (Solution A mixed in water)
Stock A
Distilled Water at 120F 750 ml
Metol 2.5g
Sodium Metabisulfite 10g
Pyrocatechin 50g
Water to 1000ml

Notes:

Mix the chemicals in the order given and stir until dissolved before adding the next chemical.

The use of the potassium bromide restrainer used in Pyrocat-HD is not needed with Pyrocat-P and Pyrocat-M because of the lower pH threshold of metol and p-aminophenol than phenidone.

Thanks ritternathan! Ha! Ha! I forgot there even was a Pyrocat-M. Now it all makes sense.

Gerald C Koch · Oct 18, 2016

John Wiegerink said:
Jerry,
I read it and re-read it, but still don't get why. Of course I only took high school chemistry and that was 50yrs ago so that might explain why I'm puzzled.

Pyrocat-HD (solution A) Distilled water 1000, Sodium Metabisulfite 10g, Pyrocatechin 50g, Phenidone 2g, Potassium Bromide 1g

Pyrocat-MC (solution A) Propylene Glycol 1000ml, Pyrocatechin 50g, Metol 2.5g, Ascorbic Acid 4g.

Now, I can understand not switching the Sodium Metabisulfite out of HD and replacing it with Ascorbic Acid since being mixed with water instead of Propylene Glycol it would need the Sodium Metabisulfite for a stable preservative. The thing I don't see or understand is why one can't mix MC version by using distilled water instead of Glycol, removing the 4g Ascorbic Acid and replacing it with 10g of Sodium Metabisulfite + 1g of Potassium Bromide. I might just mix a scaled down version of the MC with Sodium Metabisulfite+Potassium Bromide in place of Ascorbic Acid and see if it works. All it would actually be is just swapping Phenidone for Metol or Metol for Phenidone whichever way you want to look at it.

In the MC version the ascorbic acid serves two purposes. It acts as a preservative BUT ALSO acts as a developing agent. Replacing it with metabisulfite would reduce the developers strength.

Another Pyrocat question?

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