Thanks to Sean and Craig for the rock-in-the-fire idea. However, I am
writing from the Southwestern part of the country where fires are often a
big, big, no-no.

If the salt has the same properties as a rock, then you could throw the
rock on the stove and warm it up, right? Seems like the salt has a
property that the rock doesn't, which is that it diffuses heat throughout
its mass rather quickly -- which is why it is used in those space
heaters. No?

(I've done the rock in the fire -- been doing it for over forty years.)

Mark Hineline