Changes to fruit jars over the years include the introduction of a mold seam and gripper ribs along the side of the jar. Manufacturers also changed their logos over the years; this is useful for collectors to note when trying to determine the age of a jar.
Changes to fruit jars vary from manufacturer to manufacturer. Ball jars are one of the most common kinds of jars used for canning fruit and other foods. The company began manufacturing jars in 1885 and acquired many of its competitors.
Over the years, Ball introduced various changes to its jars. In the 1910s, Ball stopped manufacturing shoulder seal jars in which the lid was screwed onto the jar's shoulder. Bead seal jars, in which lids are screwed onto a jar's neck, replaced them.
Another manufacturer of fruit jars, Atlas, made changes to its jars as well. In 1882, it began manufacturing jars with wire clamp closures.
During World War II, the U.S. government required glass manufacturers to reduce the amount of glass they used in the objects they produced. This led to a rounded square shape for fruit jars.
Fruit jars are also known as canning or Mason jars. They were invented in 1858 by John Landis Mason.