Just curious if you have experience with pouring boiling water into glass jars?

[Frank]

I did not see the Pyrex brand on my old canning jars and doubt that they were Pyrex.

Here's a Wiki link:

When I worked in a lab, all our glassware was Pyrex. I'd repair or modify things on occasion but the complicated stuff went to the labs professional glass blower. It was important to anneal the glass after modifying to remove stresses. Looking at glass with polarized lenses can show stress points.

[Daniel Prince]

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.