"Don Phillipson" wrote:

Like most materials, glass expands when heated.

Pyrex does not expand much when it is heated. I had two Pyrex one
quart storage bowls (7201 05) that got stuck together. I put ice
and salt in the inner one and put the outer one in very hot water.
The temperature difference was at least 120 degrees Fahrenheit. The
bowls were still stuck together. I did not see any change in
relative size.

I have read (or seen on TV) that Russians often make tea in glass
tumblers. They put a metal spoon in the glass to keep it from
breaking. A silver spoon would conduct heat much better than a
stainless steel spoon but stainless would probably be good enough.
--
When a cat sits in a human's lap both the human and the cat are usually
happy. The human is happy because he thinks the cat is sitting on him/her
because it loves her/him. The cat is happy because it thinks that by sitting
on the human it is dominant over the human.