Black stains in darkroom

My students have suddenly gotten black stain on all their trays and even on their prints now. Any ideas what would be causing this? Did one of the chemicals go bad?

 

Edited October 12, 2017 by chris_bavaria

The white trays will develop this staining over time unless they are "washed", not just rinsed after use. A drop of dish detergent & a soft brush scrubbing will clean them up. I suspect your fixer is nearing end of life. Before each printing session, film test the clearing time of the print fixer. If it is less than 3 minutes think about replacing it. Ionic silver may not be bound with the thiosulfate & plate out on the print margins per your shot. Check the high light areas of a print. If they too are "muddled", it's the fixer. Bill

The developer tray will eventually stain pretty much no matter what. I always use the same trays for each chem- developer always goes in the same tray. I've never seen a transfer to the prints like that, or more likely the print wasn't fixed before the lights were turned on and it fogged irregularly. You've definitely got a serious cleanliness/cross-contamination/solution-life or other process problem. Be sure chemistry is never ever returned to stock solution bottles. Are you using an acid stop bath and acid fixer? If an alkaline fixer, what is the stop procedure? It would help to know exactly what chemistry and dilutions you're using. Student darkrooms tend to be subject to weird problems if everybody isn't up to speed on correct procedures. Edited October 12, 2017 by conrad_hoffman

It looks like residual silver oxide.

In addition to what Conrad and Bill wrote, you should designate some trays for developer, some for stop, and some for fixer - label them with Sharpies. Make sure they get washed, not just rinsed, after each session. With just me using my darkroom, I don't need to wash the trays every time, but a group darkroom will need more cleaning. There needs to be a serious talk about cross-contamination and how to handle chemicals. If they aren't being careful enough, someone will end up with stains on a print and it will likely be the best print they've ever made except for that stain. Ask me how I know this. :/

Since I first started in 1967, I have had the Yankee print trays, in red, white, and blue.

 

While there might be technical reasons that white trays are better for developer, I have always done it in the

flag order, red, then white, then blue.

 

And yes, I do notice some black color in the developer tray, but not enough to worry about.

It's because you don't use the trays consistently. Mixing fixer and developer causes deposition on the trays. Keep developer trays for developer, and fixer trays for fixer. And clean 'em out after use!

 

Stainless trays are expensive, but far easier to keep clean.

 

I suspect you might be over using the fixer to get stained prints. Using a stop bath might help too.

Even using one dedicated developer tray and washing it well, over the years it's turned brown. Dektol just does that to plastic trays unless you use some really hazardous stuff to clean them, which I prefer not to.

"Even using one dedicated developer tray and washing it well, over the years it's turned brown."

 

The OP's trays don't appear to show normal developer staining though. A black sedimentary deposit like that can only come from thrown silver, which is due to either massive over use of the fixer, or from solution contamination. That's unless some alternative process is being used - like wet collodion or suchlike where silver nitrate is involved.