Mason Jars are Fruit Jars, but not all Fruit Jars are Mason Jars

Several years ago, Minnetrista’s former curator of business and industrial history, Dick Cole, asked me if I knew what made a Mason jar a Mason jar. He was thoroughly surprised when I was able to tell him, because he knew that my main interest in our large collection of jars is the stories that they can tell. I am not an expert on closures and markings, although I’ve certainly learned a lot in my time at Minnetrista. I also know that I can call on Dick to answer my questions, because he loves to share his knowledge of fruit jars. Anyway, read on and you’ll know why Mason jars are fruit jars, but not all fruit jars are Mason jars.

Although he didn’t profit greatly from his invention, John Landis Mason’s name is familiar to anyone who has canned a tomato or captured a lightning bug. Mason, a tinsman by trade, invented a square-shouldered jar with a threaded screw, matching lid, and rubber ring. The threads on the glass jar allowed the lid to be screwed on, forming an airtight seal.

Before Mason invented jars with the screw top, jars generally had flat, unthreaded tops that were sealed with a flat lid held in place with wax. This seal was easily broken, allowing bacteria to enter the jar.

In November 1858, Mason received patents for his invention. Initially, he and several partners manufactured the lids, while the jars were made by glassblowers who made molds according to Mason’s specifications. Until the Ball brothers entered the fruit jar business in 1884, the companies most often associated with the manufacture of the Mason jar were Hero Fruit Jar Company and Consolidated Fruit Jar Company of New Brunswick, New Jersey.

Mason was an innovative man, and his inventions didn’t end with the screw top jar. Among other things, Mason also held patents on a baby bottle, folding life raft, and soap dish. 

Now you know. A fruit jar with a screw top, made by any manufacturer, is a Mason jar. All of those other jars made through the years that used a glass lid and wire bail or some other closure may be fruit jars, but they aren’t Mason jars.