Pyrocat-HD Solution 'A' 6 Month Life Expectancy

[Andrew O'Neill]

After 6 months of using my first batch ever of Pyrocat-HD, I've noticed that my negatives (HP5+) are getting thinner and have less stain. On the other hand, negatives that received stand development (in BTZS tubes filled with developer) were coming out extremely contrasty with zero shadow detail. The stain was great, though. Also, there were many tiny black dots all over the negatives that were only noticeable under a magnifying glass. They don't show up in contact prints (8x10 negs) but enlarged 4x5 negatives they do. I've learnt that when solution A has darkened slightly and that when it is mixed in with water along with solution B and quickly turns dark tan colour, then it is no good. I didn't realize this difference until I mixed up a new batch of solution A. There was almost no colour change when added to water along with B. My stand negatives look great once again! Moral? Keep a close eye on the colour of stock A. If it has darkened slightly and darkens even further once in solution, discard. Stock A should be very slightly tan coloured, almost clear. Good 'ol Stock B is still going strong! (Both stock solutions were kept in tightly sealed, rubberized bellows bottles in a dark, cool cupboard.)

[Ken Lee]

Did you use tap water or distilled water when you mixed the solutions ?

I use tap water, and my solution A is stored in similar conditions. While it turns a little brown, it seems to work nicely for me.

I wonder if the spots (which I see from time to time but remove via Photoshop after scanning the negatives) come from undisolved portions of Solution B - which for me has never fully disolved. I try to use only the clear solution without stirring up the "slurry" at the bottom of the bottle.

Next time I intend to use distilled water to mix the stock solutions.

[sanking]

In my own work I have found that the useful shelf life of proprely mixed Pyrocat-HD stock solutions is much more than six months. However, shelf life can be severely reduced by, 1) mixing the stock solutions with tap water, and 2) mixing the stock solutions in containers that have even the slightest bit of chemical contamination, especially if alkaline. If the Stock A solution is contaminated with even minute quanatities of an alkaline substance the solution will gradually oxidize over time. It will work well at first but after a month or two the color will change, first to a light pinkish/brown color, and then with more time to brown. My own procedure is to discard any Stock Solution A that has changed color beyond the light pinkish/brown color.

Bottom line is this. Mix the stock solutions with distilled water, and make sure that the mixing containers are completely free of any chemical contamination.

[Don Bryant]

Hi Andrew,

I can concur with your observation about part A, unfortunately I didn't adhere to the 6 month storage period and I had a batch of very very flat negatives as a result last year. Live and learn!

[chi cheung]

Hi Andrew: I had those tiny black spot on my negative once. Have you mixed developer in your darkroom lately? I am still investigating this, but as of now, I am bleming the airborne developer dust floating in the air and got settle on the film when I loading sheet film in the holder. On the stain issue, I got more stain when I re-use the Pyrocat on the second batch in semi-stand development.

Best Regards Chi Cheung, Vancouver

[Andrew O'Neill]

Hi guys! Yes, I mix both A and B with distilled water. My containers are new, never used. Had them sent over by my buddy in Japan. I think I'll discard solution A when it gets darker than that nice pinkish tan colour. Hi Chi cheung in Vancouver...is that Vancouver, BC? If so, I'm in Coquitlam....Yes, I mixed up a batch just the other day. Didn't develop film right after. I never thought about that, though but I don't think it's that. I think it must be those darn bellows bottles. But hey, who wants to keep the same batch sitting around that long anyways? The stuff is so darn cheap and easy to mix. Maybe I'll just mix up 500 ml of stock A from now on instead of 1 litre.

[David Flockhart]

Should the che,eicals be stored in light tight containers? Thanks

[chi cheung]

Hi Andrew: I am in Vancouver,BC. Is is nice to know someone in this area is doing pyro development just like me.

[Andrew O'Neill]

David, the containers aren't light tight but I do store them in the dark. The containers are dark brown.

[Chris Saganich]

I've found that the plastic, especially the bellows bottles being a thinner plastic, breaths very well, that is air will leak through the plastic cousing oxidation. I've been using glass for all my chemicals and my shelf life has increased for all my chemicals.