Two things I forgot to add to my methods pack, firstly that they only glow
when actively growing and the second that if they stop light production
because they're getting old, it's not always easy to recover. If you need to
store stuff over the weekend, do put them into a fridge.
And Bob's quite right - when we had that Kluyver flask that's on the web
site (and another 7) going, virtually everyone in the building came to visit