Pyrocat HD Shelf Life

[blevblev]

I guess I'll have to get to exposing that Tmax film....

[Jim Michael]

Thread revival time...

Assuming I have the water based version, do either solutions A or B display a physical appearance indicating they are no longer any good? What would the decay curve look like if either solution goes bad after a year (or six months, whatever), linear, log, etc? I.e. should your process time change any as it ages?

I visited the new pyrocat site, but the discussion seems to point back here.

[sanking]

Thread revival time...

Assuming I have the water based version, do either solutions A or B display a physical appearance indicating they are no longer any good? What would the decay curve look like if either solution goes bad after a year (or six months, whatever), linear, log, etc? I.e. should your process time change any as it ages?

I visited the new pyrocat site, but the discussion seems to point back here.

I will address this issue in the FAQ.

Briefly, Solution B, which is a 75% potassiusm carbonate solution, should be good for several years, and unless it is contaminated the color will always remain clean. Solution A will begin to darken from oxidation in an opened bottle after about six months. Depending on how much developer is left in the bottle the life of an opened bottle should be 9-12 months, and it will lose strength gradually. Solution A is probably ok if the color of tea, probably bad if the color of coffee. However, if Solution A is contaminated with even a minute amount of Solution B it will go bad much faster.

There is some indication that both solutions will last longer if transferred to glass bottles rather than keeping them in the plastic bottles in which they are delivered.

Sandy King

[sanking]

It is obviously a product that Digitaltruth buys from Photoformulary, as the catalog number is the same and Digitaltruth promotes the fact that it is a Photoformulary product.
Now, the only remaining question is whether your kit has been on the shelfs for a long time or if it's fresh. (Or: Did Photoformulary change the catalog number when they switched to Glycol?)

//Björn

If you buy a Pyrocat kit directly from Photographers Formulary you can be almost certain that it has not been on the shelf a long time. PF has people mixing chemicals on a regular basis and I doubt very much they keep any of the kits on the shelf for more than about a month after mixing.

Sandy King

[Jim Michael]

Thank you Sandy.

[IanG]

Living a few thousand miles from my darkroom & chemicals I have to make up batches of Pyrocat HD each time I'm back in the UK, subsequently I make up excess, and some gets stored for long periods.

The type of bottle is critical as Sandy says, the wrong plastics and the developer goes off as the walls breathe oxygen. The high grade plastic bottles used by Ilford, Agfa etc for developers are no problem at all.

The main factor determining shelf life (of the non Glycol version) is the effectiveness of the Sodium Metabisulphite in the Part A solution, it's important its reasonably fresh when making up. In a closed container Pyrocat HD lasts well over a year, with no drop in effectiveness.

However in a partially full container the Metabisulphite begins to break down faster, and the more air present the quicker, so decanting into smaller bottles helps enormously.

Ian

[James Morris]

What's the shelf life of the dry chemicals? I have to pay international shipping when purchasing Pyrocat HD & would like to store some locally for later use if possible.

[Jay DeFehr]

If you're mixing in water, it might be worth considering substituting Dimezone for phenidone, and storing your stock solution in an IV bag. The IV bags work very well for me. I use a short length of tubing stopped with a measuring syringe to dispense my concentrates. Very clean and effective. And if you're using potassium carbonate as your alkali, shouldn't you be using potassium metabisulfite instead of sodium metabisulfite in your A solution?

[Andrew O'Neill]

It's sodium metabisulfite in part A.

[John Bowen]

What's the shelf life of the dry chemicals? I have to pay international shipping when purchasing Pyrocat HD & would like to store some locally for later use if possible.

I'm no chemist, but it is my understanding that the DRY chemicals all have a long shelf life with the possible exception of Catechol. If you mix the Solution A in propylene glycol it too will last a very long time. Solution A mixed in water probably shouldn't be kept more than 6-12 months. Solution B mixed in water has a long shelf life.

I'm sure others will correct anything I've misstated. Have at it.