On Monday of this week I needed to sterilize some liquid culture medium, so I loosened the cap of the bottle to ventilate, set the bottle in a plastic tray, and placed the tray in the autoclave. (An autoclave is like a big metal oven that gets up to very high temperature and pressure and so kills any bacteria that might be hanging around inside.)
When the cycle was done I slowly opened the autoclave door and then gazed in wonderment. My bottle of medium looked normal, but it was surrounded by lots and lots of thick white foam. What on earth could have created that foam? And where was the plastic tray?
Then I realized that the plastic tray had melted completely, boiled into little bubbles, and solidified that way.
(We do have plastic trays that are made to be autoclaved; my mistake lay in assuming that this particular tray was one such.)
I had to check with various authorities to make sure the melted plastic wouldn't be a health hazard or clog an important exhaust valve in the autoclave or something. Oh, have I mentioned that I'm my lab's Safety Officer? That's me. The Safety Officer.
I ripped up the solidified plastic, scraped up the gooey traces that were still liquified, and generally cleaned the autoclave as best I could. Looks like everything will be okay, thankfully. And I kept a piece of the plastic foam as a fun memento.