I love encountering behind the scenes stories of historic breakthroughs. A big tip o’ the hat to Sabine Hossenfelder at the BackRe(Action) blog for pointing out this tale of the Stern-Gerlach experiment:
After venting to release the vacuum, Gerlach removed the detector flange. But he could see no trace of the silver atom beam and handed the flange to me [Stern]. With Gerlach looking over my shoulder as I peered closely at the plate, we were surprised to see gradually emerge the trace of the beam… Finally we realized what [had happened]. I was then the equivalent of an assistant professor. My salary was too low to afford good cigars, so I smoked bad cigars. These had a lot of sulfur in them, so my breath on the plate turned the silver into silver sulfide, which is jet black, so easily visible. It was like developing a photographic film.
A Physics Today article from 2003 goes into more depth….