PMK pyro stock A turned brown

[tkauyong]

Dear all, I made up abatch of stock solutions of PMK pyro about 2 years old. I keep the solution in 2 glass bottles, one full and the other 1/2 full. I am using the 1/2 full bottle first. Recently, I noticed that the negatives that I developed were thin. Then I found that the stock solution A is darker than usual with small precipitates. The other full bottle stock A remains clear (slightly yellow). I tried to develop with the clearer stock A solution and the negative looks fine. I know that the PMK stock solutions have very long shelf life. I would like to know what has happened to my solution. I have been using PMK for almost 10 years and have never seen these before. My last batch that I used was kept for almost 3 years and had no problem. Could this be contamination. In addition, the clear stock A that I have also shows some precipitates. Is this normal?

Thanks.

 

[Doremus Scudder]

If your PMK solution A is much darker than a straw-colored yellow, it has oxidized, either due to age or contamination, and is compromised or useless. Toss it and mix new.

This only happens to me when I've got a partially-full bottle for more than a year, but it does happen.

Best,

Doremus Scudder
www.DoremusScudder.com

 

[PhotoJim]

Partially-full bottles of A have lasted years for me (six to be precise). It is nearly inert. Contamination is far more likely.

PMK goes through some fairly obvious colour changes when you mix up solutions A and B into water. You can give this a try to see if it is alive, but I am not terribly optimistic.

 

[tkauyong]

Thanks for the replies. I have no choice but to toss it away. The brown solution still have a color change. It is colourless when dilated with water and turned brown when B is added. The film is, however, thin and like a minus 2 development. So the color change does not always indicate a good status. I think I have to check the color of the stock solution every time before I use them.

Cheers