View Full Version : Pyrocat-HD Stock solution shelf-life

Ron Marshall
10-Feb-2006, 12:28
Would anyone know the shelf-life of unopened Pyrocat-HD stock solutions A and B?

10-Feb-2006, 13:05
I mix my own rather than buy the commercial products. I've had solution A as long as six - seven months in an amber glass bottle before using it all. I don't use solution B (I just add the carbonate directly to the working solution) but I suspect it would last as long. I don't know if they will last as long in plastic as glass.


Ken Lee
10-Feb-2006, 13:08
I purchased some inexpensive glass balls, and add a few now and then to each bottle, to raise the level and keep out extra air. Cheaper than a special collapseable bottle, they make it easy to stir up the solution without introducing more air.

10-Feb-2006, 13:17

Stock Solution A should last a year or more in a partially full bottle. In a full bottle even longer. I have a liter of control Stock A that was mixed over three years ago and it still works fine. If Stock A were to go bad prematurely, say from contamination of some of the B stock, you would know it because Stock A would turn brown.

Stock B will last indefinitely.

Some people mix Stock A in glycol, which should make it last for five years or more. I mixed it that way myself a few times to make sure it worked, but have since gone back to mxing it water since I generally use up a liter or more every three months or so.


Eric Rose
10-Feb-2006, 14:21
I'm still using stuff mixed over 2 years ago. Great stuff.

Ken Lee
10-Feb-2006, 14:40
Try some in a little Orange Juice: It's dee-licious !

Walter Foscari
10-Feb-2006, 14:41
"Some people mix Stock A in glycol, which should make it last for five years or more..." Sandy, do you mean sobstituting glycol for water? Where do you obtain that? same mixing procedures?


10-Feb-2006, 15:44

Most people use propylene glycol. I purchase it from http://chemistrystore.com, but I believe that places like Phtographers Formulary and Artcraft also carry it.

Yes, same mixing directions. You mix as with water, except you must heat up the gly col first to about 150F for the pyrocatechin and phenidone to dissolve. Place the glycol in a pyrex container and heat in a water bath over the stove. Once it heats up to 150F add the pyrocatechin, stir until is dissolves, then add the phenidone. Mix the sodium metabisulfite and bromide separately in a small container of hot water hot, then when dissolved add this to the glycol solution containing the pyrocatechin and phenidone. This solution will have about the same permanece as a HC-110 stock solution, which is to say for a very, very long time. Use it just as you use Stock Solution A mixed in water.

No point to do this with Stock B since it will last indefinitely anyway.

You could also substitute ethylene glycol, available as anti-freeze, but I feel more comfortable with the propylene glycol since it is found in many foods so should be very safe


10-Feb-2006, 17:36
I have pyrocat in liquid form, from B&S. The A solution is a dark, almost like coca- cola color. Is this A soluting Bad?

10-Feb-2006, 18:16

I have never used the B&S Pyrocat-HD kit and don't know how it performs or what it looks like, or how it performs. I have used the kit from Formulary, and it mixes up with a very clear Stock A solution, perhaps with a hint of a pale yellow, just as my Stock A looks when mixed from scratch. And my Stock A solutions keeps this color indefinitely. In fact, the three year old control bottle I have is still almost completly clear.

Is there any possibility that you may have contaminated Stock A with a minute quantity of Stock B? If so, the result would be a very gradual shift in color of Stock A from clear to light amber to darker amber to coffee brown to dark brown. Beyond light amber I would not trust the solution.

Andre Noble
11-Feb-2006, 14:58

Mixing the part A in glycol for enhnaced storage life seems like a good idea. What prevents you from askin PF to offering the glycol form as the standard form of part A in their pre-mixed kits?

P.S. I had problems with self contamination/ or premature aging of my pyrocat in past resulting in total failure of the developer, but recently ordered the 500ml version instead of the 100ml pre-mixed kits from PF. Since the plastic brown bottles they come in breath air and lead to fast oxidation of the developer, I immediately strored brand new pyrocat part A and part B in two 500ml Grolsch beer type, rubber stopped glass bottles.

Will let you know how this works out.

Jay DeFehr
11-Feb-2006, 19:05
Hypercat is made up in glycol and avoids these kinds of keeping issues entirely.


11-Feb-2006, 20:12

I will speak to PF to see if they might want to mix Pyrocat-HD in glycol. That would certainly eliminate any storage issues, though by comparison to virtually all other commecial formulas the Pyrocat-HD stock solutions are remarkably stable, assuming they are mixed correctly and are not contamined by the user.

For now, however, persons who want stability on the order of years should mix in glycol. Not a big deal, since mixing in glycol is for all practical purposes no more complicated than mixing in water.

Jay DeFehr
12-Feb-2006, 12:49
There is only one advantage to making up the stock A solution in water, and that is economy. Water is cheaper than glycol, and if the stock solution will be used before it goes bad, or is contaminated, one can save a few pennies, but that seems a false economy. A glycol solution not only has much superior keeping properties, but is also far more resistant to cross contamination. Hypercat, unlike Pyrocat HD, was formulated specifically to be made up in glycol, and so all of the ingredients dissolve quickly and easily at around 150F, and the stock solution contains no water. There are workarounds that allow Pyrocat HD to be made up in glycol, including mixing at very high temps, or mixing two solutions together to make a water/glycol solution. Either is better than an aqueous solution, but both represent a compromise compared to Hypercat.


Ken Lee
12-Feb-2006, 17:41
Jay -

I would love to see some photos whose negatives were developed in Hypercat. Are any available on-line ?

Jay DeFehr
12-Feb-2006, 19:15
Hi Ken.

There are some in my apug gallery, but it's only viewable by apug members. If you're not a member, I could email a few images directly.