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


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

the bottling process creates a lower pressure environment inside the jar that causes the air outside the jar to press the button down. once you open the jar for the first time, the air inside the jar mixes with the air outside the jar and they are equal. so unless you can seal the jar again and then lower the pressure inside the jar, it’s never going to pop again.

I dont know the specifics. But i believe that when they are putting the lids on the product, they seal the jars under pressure. So when you open it for the first time, they release the pressure and the lid is popped.

It’s all about air pressure during the jarring process. Normally products jarred are pasteurized to kill bacteria. When the jar is heated and then cooled, the air pressure inside basically pulls that button. When you twist the top, you release the pressure and the button pops. Does this help?

When the jar is sealed, there is a vacuum on the inside. This means the pressure outside the jar (air in the room) is greater than the pressure on the inside. The outside air exerts a force on the lid, just as if your finger would when you try to hold down the poppy thing. When you open that jar, air rushes in and the poppy thing is raised, because the pressure has equalized. Afterward, putting the lid back on just traps the air with the same pressure inside, so there is no force pushing down on the poppy thing.

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.