How does the button on my pickle jar pop once opened for the first time?

Question

I have this button on a few jars around the house like jam jars, they are always glass. Why does the “button” pop once and never again?

In: Physics

Answer 1

I actually know a more precise answer from canning with my Grandma.

If you’re canning a food, like pickles or jams, using Kerr jars, one of the last steps is to heat up the food before putting it in the container. This not only cooks to food to help prevent botulism, but also creates a low pressure zone inside the jar due to the heat, so that when everything cools back down, the lid self-seals onto the jar until it’s opened again.