Glass Jar with Bronze Pop Top Lid - 100ml

100ml glass jar with bronze pop lid. 

The benefits of the pop lid: When being canned the ingredients are put into the jar hot before a lid is put on. When the ingredients cool it creates a suction that pulls the lid down. When you open the lid and hear a pop the air is coming in to fill the low pressure inside, which indicates that there was a good seal.

If there is no pop that means that there is no longer low pressure in the jar, this could be because it was never sealed properly, or the contents have gone off despite the seal and created gas inside the jar.