“Had an undergrad who ‘autoclaved’ stuff from our lab by drawing black lines on the autoclave tape with sharpie and moving it to the clean area. When I noticed the tape looked funny, I knew exactly what had happened, and nearly died laughing.” [source]

Laughable? Most certainly! But also more common than you think—much more common. And potentially dangerous.

Take the Time to Explain Autoclave Tape

We need to remember that autoclave tape isn’t intuitive to work with. It has no household equivalent—and autoclaving itself is often treated like pixie magic—even by otherwise quite competent researchers.

According to Philip Berriman, an instrumentation technician at California State University (Fullerton), you really do have to slow down for a moment and be sure everyone working in your lab understands:

“Just because autoclave tape changes color, that doesn’t mean it’s sterilized—it just means the outside of the item has reached the temperature of interest. It doesn’t mean the core of your sample has, and it doesn’t mean that the coldest part of your sample has held at the required temperature.”

The tape can even give a false sense of security, because even more important than temperature is steam saturation:

“It can be at the temp you need, but if it’s not saturated with steam, it takes something like 16 hours [to sterilize] … instead of 15 to 20 minutes. It’s that incredible energy from saturated steam versus dry air that makes an autoclave so magical. All this tape says is that this has been in the autoclave and someone turned it on. That’s all you know. You don’t know it’s sterile.”

BONUS: This thread offers some good tips for easily removing gooey old steamed-on autoclave tape.