These jars were made from 1904 until World War II, when they were discontinued in favor of the Kerr Glass Top. The line was reinstated about 1946, and production continued until at least the 1980s. All of these jars had the Mason beaded neck style, although the actual seal was at the lip or rim of the jar.

How hot can a Mason jar get?

240-250 degrees Fahrenheit A Pressure Canner brings jar temperatures up to 240-250 degrees Fahrenheit. This temperature can be reached only by creating steam under pressure. At this temperature we can be assured that 100% of bacteria is killed.

Why are Mason jars popular?

Mason jars remained popular during World War II, as a way to preserve the bounty of the government-encouraged Victory Gardens. Yet the rise of refrigeration in the post-war years pushed people to freeze rather than can. As the jar became less of a necessity, the culture surrounding it changed, Kelly writes.