On 09/09/2013 10:38, Dave Liquorice wrote:
On Sun, 8 Sep 2013 20:41:55 +0100, Janet wrote:

Clearly you are one that needs to be made aware of the dangers.
If you rapidly depressurise a pressure cooker and there is a
closed
container inside, the container may explode due to over pressure
and/or
thermal shock.

If a closed container in a pressure cooker hasn't already exploded...

It should be mostly OK provided that the pressure in the container is
coupled to the pressure in the autoclave the boiling point of the water
inside it will also be raised. Conversely the water inside the container
will boil until it matches the working pressure in the cooker.


AIUI the containers are not sealed until they have been through the
high temperature/pressure process and cooled to be accessable at room
pressure.

Any lids etc also need to have gone through the high temp/pressure so
presumably they are loosely fitted to keep most of the water/steam
out of the product and tightly fitted whilst everything is still very
hot.

I think for home canning it is supposed to be fully sealed and then
aggressively pressure cooked. Not sure how well Killner jars would stand
up to it. We blanch and then freeze pea & bean gluts.

Who said "rapidly depressurise a pressure cooker"?
Take it off the heat. Do nothing. That's how easy it is.
The pressure cooker will depressurise all by itself.

Once you take the weights off... Will the pressure drop to
atmospheric in a sensible time scale once removed from the heat and
weights left on? I guess you let it cool 'till it stops hissing from
the weights then keep trying to lift the weights without it blowing
too much, FSVO "too much" steam out.

I've no great experience of pressure cookers, My Mum didn't like 'em
so we never had one at home.

Sudden decreases in pressure are a very bad thing as flash boiling
inside some thick goupy stew or soup inside one is a disaster!

I have distant recollections of conical fountains of scalding soup
flying up into the air plastering the kitchen ceiling and bouncing all
over at my aunts. They are fine if used correctly but there is scope for
considerable excitement if you make a mistake at high pressure.

ISTR some kind of emergency pressure release system triggered on it.

--
Regards,
Martin Brown