autoclaving - (May/28/2014 )

Dear all,

I found the following blog: http://biologyze.com/2012/03/01/a-day-in-the-life-march-1-2012/#comments

Now I wonder: how many of you here uses aluminum foil like that? Is this normal ? It seems idiotic to do it like that. I never use aluminum foil. I just close the bottles after autoclaving and never get contamination.

A second question: how do you guys sterilise solid materials that are placed in bottles. Like for example pearls that you use to spread bacteria on a plate.

I put them in a bottle , but should I keep the lid a bit losened too or not? Losening the lid is to prefend the bottle to burst when working with liquids, but with something solid in it? I can only think that the lid should be a bit losened so water/steam can enter the bottle? Or is this not needed to sterilse the beads?
 

Hi,
It is not obligatory.  For pearls and other solid material it’s better to leave it loose and let it being cold inside the autoclave and then tight it.

Ensyeh on Wed May 28 19:41:46 2014 said:

Hi,
It is not obligatory.  For pearls and other solid material it’s better to leave it loose and let it being cold inside the autoclave and then tight it.

why?

It has very simple reason. When you leave the materials to opened aoutoclave you let them to being dry in a hot place slowly, if not you have to close the bottles and water drops remain in the bottle for  several days and myself don’t like it.

Ensyeh on Wed May 28 20:11:56 2014 said:

It has very simple reason. When you leave the materials to opened aoutoclave you let them to being dry in a hot place slowly, if not you have to close the bottles and water drops remain in the bottle for  several days and myself don’t like it.

But then you have to close it after you placed it in a hot oven to remove all the moist from the bottle?

I am confused now.

You mean: put the bottle with pearls in the autoclave with the lid a bit opened, after autoclaving put the bottle in an oven to dry it and then close it after drying?

For all containers that can potentially seal - you need to have the lid loose so that the steam can get in and do the sterilizing, there are no exceptions to this rule. The only time you might break this is if you are doing a heat only sterilization, in which case you should use an oven and be heating to 200 C or more rather than an autoclave.

Regarding tightening lids after autoclaving - for most solid materials (as opposed to liquid media) you want them to be dry after the autoclaving, especially if the end use might be altered by the presence of water (extra water added to your plates?).  Often drying is done in an oven at 60-70 C, in which case the lids should be loose to allow condensation to evaporate.  If you don't require them to be dry, then there are 2 schools of thought - 1) Tighten immediately so as to prevent any contaminants from being drawn into the bottle as it cools and 2) allow to cool slowly with lid loose so that you don't have a sudden influx of (potentially) contaminated air when you loosen the lid, as you would get with scenario 1.

bob1 on Wed May 28 21:04:16 2014 said:

For all containers that can potentially seal - you need to have the lid loose so that the steam can get in and do the sterilizing, there are no exceptions to this rule. The only time you might break this is if you are doing a heat only sterilization, in which case you should use an oven and be heating to 200 C or more rather than an autoclave.

 

Regarding tightening lids after autoclaving - for most solid materials (as opposed to liquid media) you want them to be dry after the autoclaving, especially if the end use might be altered by the presence of water (extra water added to your plates?).  Often drying is done in an oven at 60-70 C, in which case the lids should be loose to allow condensation to evaporate.  If you don't require them to be dry, then there are 2 schools of thought - 1) Tighten immediately so as to prevent any contaminants from being drawn into the bottle as it cools and 2) allow to cool slowly with lid loose so that you don't have a sudden influx of (potentially) contaminated air when you loosen the lid, as you would get with scenario 1.

I see what you mean.
And what if you add the pearls, still being a bit moist, would that be enough? So the "steam" would already be inside the bottle.

In an oven of 60°C I am assuming there is no risk on contamination?

And do they need to be dry: well its best they are dry, easier to use them to spread the bacteria on the plates, but dry or not, they should be sterile anyway.
 

Technically they don't really need to be dry, but it would probably make the spreading a bit more consistent if they are.  The steam would already be in the bottle when you use them- though by that time it would have condensed.

Drying ovens can be at a range of temperatures, but the amount of water left over from autoclaving should be small enough that it will be gone with an overnight drying.  60 will inhibit most bacteria, especially in the absence of water. 

Just a note: many bottle caps (like the ones on Corning GL45 bottles) cannot be heated above about 140. If you put them at 200 in a heat sterilizing oven, they melt and make an art object.

They sell red caps that are heat resistant, but you usually have to make this mistake at least once.