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Opening autoclave


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#1 bioke

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Posted 23 June 2014 - 11:59 PM

Dear all, if you sterilise something and the autoclave is still at 96-99°C , do you already open the autoclave?

 

I am not talking about safety, this is not an issue , there is no pressure and its safe to open it. I am however talking about "is it good" for the materials inside? For solid stuff it does not matter, but for liquids ? Is the sudden drop in temperature when taking thins out perhaps a problem?

 

 



#2 bob1

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Posted 24 June 2014 - 12:17 AM

Its not a problem, but you might, if the temperature is too high get a boil-over when you go to shift the bottles.

 

You might loose a bit of fluid to evaporation too.



#3 bioke

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Posted 26 June 2014 - 12:49 PM

Exactly what I was thinking!

Not sure why some people in the lab insisted on not opening it because it would be bad for the media.

 

Its not a problem, but you might, if the temperature is too high get a boil-over when you go to shift the bottles.

 

You might loose a bit of fluid to evaporation too.

 



#4 bob1

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Posted 27 June 2014 - 03:27 PM

Media are the most sensitive to these sorts of things - minor variations in salt concentration can make a big difference to how well your cultures grow.

 

Loss of liquid by evaporation would lead to increased salt concentrations - if you close the bottles pretty much immediately it won't be too much of a problem.



#5 bioke

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Posted 28 June 2014 - 11:51 AM

I can hardly imagine that this would make such a big difference for yeast and bacteria.

I can also not imagine you would get so much evaporation! I do however close the bottles right after I open the autoclave, so normally there is no evaporation.

 

Media are the most sensitive to these sorts of things - minor variations in salt concentration can make a big difference to how well your cultures grow.

 

Loss of liquid by evaporation would lead to increased salt concentrations - if you close the bottles pretty much immediately it won't be too much of a problem.

 



#6 bioke

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Posted 29 June 2014 - 03:14 AM

reading your reply back: what is it that you actually mean with this?

Boil over because you shift the bottles?

Its not a problem, but you might, if the temperature is too high get a boil-over when you go to shift the bottles.

 

You might loose a bit of fluid to evaporation too.

 



#7 bob1

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Posted 29 June 2014 - 01:13 PM

It's called superheating - you can quite commonly get this in microwaves, so you may have seen it there.  It's where the liquid looks like it isn't boiling, but in reality it is actually above boiling point, so if you move it or bump it, it creates cavitation that causes nucleation points for bubbles that then cause the liquid to boil very very rapidly (sometimes almost explosively) so it will come out the top of the bottle at >100 C.



#8 bioke

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Posted 30 June 2014 - 10:50 AM

Ok, thanks a lot.

Is it dangerous? Explosive? Can the bottle explode?

So its best to wait a bit longer to open it!

 

It's called superheating - you can quite commonly get this in microwaves, so you may have seen it there.  It's where the liquid looks like it isn't boiling, but in reality it is actually above boiling point, so if you move it or bump it, it creates cavitation that causes nucleation points for bubbles that then cause the liquid to boil very very rapidly (sometimes almost explosively) so it will come out the top of the bottle at >100 C.

 



#9 hobglobin

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Posted 30 June 2014 - 10:57 AM

Ok, thanks a lot.

Is it dangerous? Explosive? Can the bottle explode?

So its best to wait a bit longer to open it!

 

It's called superheating - you can quite commonly get this in microwaves, so you may have seen it there.  It's where the liquid looks like it isn't boiling, but in reality it is actually above boiling point, so if you move it or bump it, it creates cavitation that causes nucleation points for bubbles that then cause the liquid to boil very very rapidly (sometimes almost explosively) so it will come out the top of the bottle at >100 C.

 

It's dangerous when the hot fluid gets in your face or other body parts, when it leaves the flask during the boilover (similar you can see when you melt agarose in a microwave and it's hot enough to boil but starts boiling first immediately when you shake or stir it a bit). The flasks won't explode (only during autoclaving when you closed the lid completely).


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#10 bioke

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Posted 30 June 2014 - 11:31 AM

 

Ok, thanks a lot.

Is it dangerous? Explosive? Can the bottle explode?

So its best to wait a bit longer to open it!

 

It's called superheating - you can quite commonly get this in microwaves, so you may have seen it there.  It's where the liquid looks like it isn't boiling, but in reality it is actually above boiling point, so if you move it or bump it, it creates cavitation that causes nucleation points for bubbles that then cause the liquid to boil very very rapidly (sometimes almost explosively) so it will come out the top of the bottle at >100 C.

 

It's dangerous when the hot fluid gets in your face or other body parts, when it leaves the flask during the boilover (similar you can see when you melt agarose in a microwave and it's hot enough to boil but starts boiling first immediately when you shake or stir it a bit). The flasks won't explode (only during autoclaving when you closed the lid completely).

 

 

Oh ok!

Thats not an issue. I always close the bottles when they are still standing in the autoclave. Never had problems with liquid coming out of the bottle.

Just to be sure, I'll wait a bit longer in the future.

 



#11 El Crazy Xabi

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Posted 30 June 2014 - 07:44 PM

Liquid superheating in the autoclave usually happens if you:

  • autoclave bottles completely closed
  • autoclave bottles with the caps not loose enough to compensate the pressure/vapor with the autoclave chamber
  • open the autoclave before the content in the bottles have time to compensate the pressure in the chamber once you open it, even if the lids are loosely attached
  • close the bottle still very hot (right after the pressure in the autoclave drops, with a temp still above 90-95° C) and you open it again soon

Otherwise should not be a problem






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