Why do we call it canning if we’re putting stuff in glass jars? The answer has to do with when the technique was discovered. The process of canning came about in the late 1700s, when thin glass jars were used. Factories soon switched to metal cans because they were durable and better for shipping. But after Mason jars came about in the mid-1800s, the process of preserving things at home kept the name canning. This is part of a complete episode.