Hi
Can anyone tell me the shelf life of stock solutions of Pyro HD? I have some stock that I mixed about 9 months ago and wanted to go ahead and use it but was not sure of it's life span. thanks
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Hi
Can anyone tell me the shelf life of stock solutions of Pyro HD? I have some stock that I mixed about 9 months ago and wanted to go ahead and use it but was not sure of it's life span. thanks
You should visit pyrocat-hd.com for a list of resources. Ken is doing a great job with the site.
If the metabisulphite used was reasonably fresh when it was made up and in the right type of bottle at least 18 months. That's from personal experience.
In glycol then indefinitely.
Some plastic bottles allow some oxidation to take place, but the higher density bottles used by Ilford/Agfa.Kodak etc for developers are fine. I made the mistake a few years ago of storing may first batch in small laboratory sample bottles thinking this would be better only to find Pyrocat HD lasted less than 6 months in them.
Old Rodinal bottles are ideal :D
Ian
Ian,
Could old or oxidized Pyrocat result in uneven development?
Not really just unwanted additional staining, but if it's turned a string greenish blue colour then possibly.Quote:
Originally Posted by chris_4622
Ian
My experience with PC-HD in glycol stored in brown glass is that it "weakens" after two years or so. An image is formed but with much less contrast than expected. A fresh batch mixed from the same set of raw chemicals resulted in the expected results on the remaining sheets of film.Quote:
Originally Posted by IanG
I assumed (rightly or wrongly) the "A" solution with the developing agents was the culprit rather than the potassium carbonate "B" solution.
Ian, you imply a potential issue with the metabisulphite...can you explain please?
Dave
There are a few tricks to making these glycol solutions last forever, and they all involve keeping water out of the concentrate:
1. Dry your chemicals in the oven before mixing. Weigh after drying.
2. Heat your glycol to drive off any water, allow to cool in a rubber stoppered flask before mixing.
3. Store your concentrate in an IV bag with a short length of tubing, stopped by a measuring syringe.
By eliminating as much water as possible from the mixed concentrate, and by preventing water from being absorbed into it after mixing by exposure to airborne moisture/humidity, you will get maximum shelf life from your concentrate.
Metabisulphite contains free SO2, when it's fresh it gives of a a strong, sharp, acidic smell which is the SO2.Quote:
Originally Posted by David Swinnard
In the US Sodium Bisulphite is more common than Sodium Metabisulphite probably due to differences in how it's produced compared to Europe. In some cases they are interchangeable but not when used as an anti-oxidant.
It's partly down to purity as Bisulphite is typically a mixture of Bisulphite and Metabisulphite.
Sodium Bisulphite
Sodium Bisulfite 58 - 99%
Sodium Metabisulfite 1 - 42%
Sodium Metabisulphite
Sodium Metabisulfite 100%
Sodium Bisulfite < 0.001%
Metabisulphite is far stronger as a preservative which is why it's used in the wine making industry and food preservation rather than Bisuphite and in certain developer formulae.
Where a formula uses Bisulphite you can safely use Metabisulphite but not vice versa.
Metabisulphite deteriorates breaking down over time so the fresher the better as a preservative.
Ian