autoclaving - a lot of fluid lost? (Aug/31/2009 )

eberthella on Sep 2 2009, 11:20 AM said:

Is there no way to ban this clown?

Anyway on the topic of autoclaving... Does anyone do what we do and just place the top on the bottle and tape it down? I dont know if this is the best way but Ive never had any problems with it...

Kami23 on Sep 3 2009, 01:39 PM said:

What do you mean?

You close the bottle completely and then tape the top? Or you open the top 1/4 (orso) and then tape it down?
I cant imagine that the tape would stop the gas? Or even the boiling fluid?

pito on Sep 3 2009, 02:02 PM said:

nope i mean dont close the bottle at all with the screw fitting, just secure it with the tape... it lets the cap boing about a bit and theres no real risk of explosion (so long as you dont tape it down too tight)

Kami23 on Sep 3 2009, 04:01 PM said:

And you think that would help ?
It seems odd that if you let the top lose and tape it down you would lose less fluid, gas then when screwing the lid on and letting 1/4 turn open.

Not one to wade into this argument but aside from making sure the vessel is large enough and the top is loose, have you made sure you're not autoclaving on the solid cycle? You shouldn't be losing that much liquid to care about otherwise.

Astilius on Sep 7 2009, 01:14 PM said:

Honeslty, I do not know.

I simply have to press the "on" switch and that is it.
Its 15 minutes on 121°C ... So what kind of cycle is that?

The difference between a solid cycle (also known as a gravity cycle) and a liquid cycle is how fast it vents at the end of the run.
So, although the autoclaving conditions are different you can't tell from looking at them alone (if you follow me).

Do you have a lab tech that can explain the autoclave to you?

What might be happening is that the autoclave is venting at the end of the cycle and making the liquids inside boil over due to sudden pressure loss.

Rule of thumb: You can autoclave solids on a liquid cycle but you cannot autoclave liquids on a solid (gravity) cycle.


Not all autoclaves have solid cycles and you just need to wait until they equilibrate to atmospheric pressure. Check the instrument's manual as a first resort.

In this specific case, I'd probably go with filter sterilizing the solution. However, that isn't always feasible. If you are preparing something like agar plates, you have to autoclave at least the agar/water solution to get the agar into solution. If I have to add something that isn't autoclavable to something that must be autoclaved, I'll autoclave only those components that must be autoclaved and filter sterilize everything else. That way, I'm a least minimizing the potential for losing the more pricey reagents.

I've autoclaved liquids a couple of different ways, always on the liquid cycle. During my undergrad, we had 2 autoclaves: a big honking thing that made horrible noises and a little one that looked like a rocket ship. A few times when I autoclaved solutions in the big one, the bottoms of the glass bottles blew out. I was certain that the caps were on loosely, at least a full turn. My PI told me to place the bottles in water to prevent them from blowing out. She thought that the metal rack the bottles were on was cooling at a different rate than the solution and the temperature difference was causing the glass to break. When I autoclaved the bottles in a water bath, they never broke and I noticed that it greatly reduced any solution loss. From that point on, whenever I autoclaved liquids in the large autoclave I placed them in a water bath. I never had a problem with massive solution loss or glass breakage in the little autoclave. I guess the type of autoclave can also affect solution loss.