This is true. But if there is a jar on top of another one then the top jar will weigh down the other one and you won't know if you have a bad seal until it's too late. If you catch a bad seal within 24 hours, usually the food can be either put in the fridge, recanned, or eaten right awayI've never canned, but I have READ that if one removes the ring then a broken seal becomes more apparent.