I just started experimenting with making slants in test tubes. My tubes are 16x100 mm. I got these flange caps:
which are supposed to be entirely water/air tight, and I don't doubt that they are, however my original reasoning for getting them didn't take into account the gas produced by the yeast as it grows on the slant surface.
I came home from work after the first day and all four of my WLP300 culture tubes had no caps on them - at first I suspected my roommates tampered with them until I realized that all the caps were strewn about the kitchen, having obviously blown off the tubes. Since then I have been periodically bleeding the pressure by popping the lid just enough to release it, but they still manage to pop the tops if I don't get to them often enough. Now I realize that having the tops pop is a great way to get them contaminated, but since I'm still experimenting at present I'm not as worried about it, I may not even use the yeast I'm culturing in these particular slants anyway.
Anyway... Does anyone with more slant experience have any suggestions on better test tube stoppers, or methods for going about this during the yeast growth period? I was thinking that if I only seat the stoppers to the first flange, they might be able to leak gas well enough, and I can cap them fully after they're done growing and I chuck them in the fridge, but they might manage to blow the caps off anyway. I also saw the idea of sterilized cotton balls being used to plug the tubes at first, and switching to stoppers later on, but didn't see any real 'yea or nay' conclusion on the matter... but then again I suppose anything would be better than having my stoppers popping off several times a day...