This is a bit bizarre. I was developing some sheet film this morning in trays. When I put each sheet of film into the stop bath, it briefly gave off light. Yes, you read that right – each sheet of film glowed briefly as I put it in the stop. I don't think it was a chemical reaction, because after I was finished I used a pipette to squirt a little bit of used developer into the stop bath, and no light was produced. Has anyone seen anything like this before? Could be static? Do you have a better idea? For what it's worth: the stop was dilute acetic acid, the developer was John Wimberley's WD2H+, and the film was FP4+. [Update] I repeated the test with a water stop bath and no other changes. Everything worked as would be expected.