autoclave and media question - (Jul/07/2006 )

recently i have been setting up a small water quality lab and one thing I will be testing for is fecal coliform. So i went and ordered some dehydrated media and an autoclave and weeks later i finally get the stuff and i start reading the manual for the autoclave and it does not have the slow cool down function for liquids. from what i have read it seems that my media will be boiling out of the containers

how bad is the boiling over?

sorry for the stupid question but I am very new at this (fresh out of school) also the one with the cool down feature cost more and i am running on a very small budget and it would take away some testing time of sending this one back and waiting for the new one.

I think that is depends on your type of autclave and the best thing is the consult the manual, but I will tell you what I know from experience

some types of autoclaves have a valve (can't remember what it's called, but it should be in your manual..."needle"-something) that can be adjusted in order to increase the exhaust time

the autoclave where I work is like that. for most liquids, buffers, etc it's fine if you don't overfill (50% to 75% of the container volume is good). for agar-media, it will boil over every time if you don't take a few precautions. you can autoclave your agar in a large tub with water in it, and add a bunch of big bottles of tap water. if you increase the thermal mass of your load, without putting in too much agar media (too many bottles and you have to cook it long enough to carmelize the media to get the damn agar to melt properly) adding the water seems like the easiest way to me, but be careful not to dump boiling liquid all over yourself when unloading ....the extra thermal mass cools more slowly, increasing your exhaust time in a rough sort of way