How do I test whether my food jar's insulation is faulty?
To test whether your food jar's insulation is faulty, place a thermometer in the food jar and fill it with water. Afterward, place the food jar in a pot of boiling water.
Check the temperature of the water in the food jar after 10 minutes. If it's still above 80°C, then your food jar has an excellent insulating layer around it – which means you're good to go!