Important for all glass cups:
If you use a carbon tablet, light one, put it inside, wait a while for the glass to warm up gradually.
When it is hot, you can then put another carbon tablet.
If using embers from the fire: Put the embers very little by little so that the glass gradually heats up.
If the glass bowl is too quickly filled with embers from the fire, it runs the risk of expanding very quickly and breaking.
Little by little and slowly ….
Use a tissue for the handle …