We’ve spoken at length about the follies of foil, and regularly help customers kit out autoclaves precisely suited to their specific tasks. But there is one thing that any lab can do at no cost— TODAY!—that will massively boost the effectiveness of their steam sterilizer:
Autoclave large beakers, flasks, and cylinders on their sides—especially Erlenmeyer flasks and tall graduated cylinders!
Lying Down Does a Better Job!
As Philip Berriman, an instrumentation technician at California State University (Fullerton), explains:
“Orientation of the vessel is huge, to avoid trapped air. The worst case scenario us an upright Erlenmeyer flask: Huge at the bottom, lots of air down there, skinny at the top, and the steam always has to start at the top and work its way to the bottom, displacing air. Well, the air has no place to go and there’s a ton of it at the bottom, so the whole bottom of your Erlenmeyer flask doesn’t get sterilized if it’s upright, unless you wait a just ungodly amount of time for the steam to mix in with the air. Then they add tight foil [covering the top of the flask] that they call “loose”?!? Now you’ve just taken [the chances of proper sterilization] to super impossibility.”
Phil has run trial cycles in his own lab, using both spore vials and T-T-S (time, temperature, steam saturation) integrator strips to validate sterilization. He found that one liter straight-walled beakers and Erlenmeyer flasks never failed to sterilize when autoclaved for a standard 30-minute gravity cycle while lying on their sides. If they were standing vertically, these same beakers usually were not fully sterilized by that same 30-minute gravity cycle.
Add loose foil to those vertical beakers? They always failed to sterilize during a standard 30-minute gravity cycle.
Two No-Cost Lab Autoclave Procedure Improvements for the Price of One!
So, really, we have two no-cost improvements to your lab autoclave procedure:
- Autoclave beakers lying horizontally
- Stop covering everything with foil!