Peter A wrote:
>
> Complete claptrap. What part of "sterile" do you not understand?

It's not sterile. As the pot cooled, the contraction
of the air inside the pot would have drawn in
unsterilized room air containing bacterial spores.

I used to prepare Petri dishes in my kitchen
using a pressure cooker, and I know how difficult
it is to prevent contamination. One of the lessons
I had to learn was to prevent unsterilized air
from entering the Petri dishes while they
were cooling.