Jeff Liebermann writes:
On Fri, 17 Oct 2014 11:45:50 -0400, micky
wrote:
Also, if there were a soft plastic inside liner, I
would expect it to melt from the heat of gas flame at the bottom.


Have you never boiled water in a styrofoam cup over an open flame?

One can. The water keeps the temperature of the foam below its
melting point.