Even better: purchase an inexpensive strap wrench with a rubber strap (something like this) and keep it in the kitchen for stubborn jar lids. For the jar lids that even a strap wrench alone can't quite open, I've had success by using the strap wrench on the lid while holding the jar itself with a silicone oven mitt (or oven mitt with rubberized grip--the rubber band trick might work here as well).
Even better: purchase an inexpensive strap wrench with a rubber strap (something like this) and keep it in the kitchen for stubborn jar lids. For the jar lids that even a strap wrench alone can't quite open, I've had success by using the strap wrench on the lid while holding the jar itself with a silicone oven mitt (or oven mitt with rubberized grip--the rubber band trick might work here as well).