Put the jar in a teatowel layed side not upright of course lower it in very hot water and the lid may come off. Wait about 4mins if it doesn't lift it out. Hold it in the tea towel and with another cloth/tea towel ease the lid off. DON'T SUBMERG IT IN COLD WATER OR HOLD IT UNDER COLD TAP AFTER LIFTING IT OUT IT MIGHT CRACK.
Found that out at school yr xxxx with test tubes heated to show us what would happen with hot glass suddenly coming in contact with cold water the crack to destruction. A tip I've been told is to coat the glass lid/ rubber seal with thin smear of vaselene [petrolium jelly] that prevents them sticking and does no harm to whats in it.
Bob, September 2010
