MASON JARS
The age and rarity of a jar can be determined by its color, shape, mold and production marks, and closure. Most antique jars that are not colorless are a shade of aqua known as "Ball blue," named for the prevalent jar maker. Colored jars were considered better for canning use, as they block some light from reaching the food, which helps to retain flavor and nutritional value longer. More rarely, jars will turn up in amber, and occasionally in darker shades of green. Rarer still are cobalt blues, blacks, and milk glass jars.
History
The earliest glass jars were called wax sealers, because they used sealing wax, which was poured into a channel around the lip that held on a tin lid. This process was complicated and error-prone, but was largely the only one available for a long time and widely used even into the early 1900s.By far, though, the most popular form of seal was the screw-on zinc cap, the precursor to today's screw-on lids. The earliest successful application of this was discovered by Mason and patented on November 30, 1858, a date embossed on thousands of jars. Jars with "Patent Nov 30th 1858" were made in many shapes, sizes and colors well into the 1900s. Since they were made in such quantity and used for such long periods, many of them have survived to the present day.
Another popular closure was known as the Lightning closure, named after the first jar to use it, which was embossed with "Lightning" on the side. More commonly, this is often known as a bail closure, or French Kilner — it consists of a metal wire arrangement with a lever which, when pivoted downward against the side of the jar, applies leverage to a glass lid, clamping it down over a separate rubber O ring. While these jars are still sold for storage, they are now rarely used for canning
In the 1860-1900 timeframe, a great many patents were issued for various jar closures. The more esoteric closures were quickly abandoned, and can fetch high prices in today's antique market.
The Mason jar was invented and patented in 1858 by Philadelphia tinsmith John Landis Mason. Among other common names for them are Ball jars, after Ball Corporation, an early and prolific manufacturer of the jars; fruit jars for a common content; and simply glass canning jars reflecting their material.
While many jars carry an embossed date of 1858, most do not date back that far. Jars that carry this date may have actually been manufactured as late as 1920. Before 1915 mason jars were made from blown rather than molded glass. Blown glass jars have a round raised area, or pontil scar, on the bottom while molded glass exhibits telltale mold seams. Blown glass jars are more valuable than molded ones. Values of collectible mason jars may range from around $7 to $10 all the way up to hundreds or even thousands of dollars. Having the original lid with the jar can increase the value by as much as 50 percent.
Collectors frequently refer to these numbers as "mold numbers." However, in some cases, this term oversimplifies what the numbers represented.
Originally when jars were blown by hand, the number represented a specific glass blower and his team. At the end of the day the blower and his team would get paid for the amount of jars they produced as determined by the number of jars made with a given number on them. I.E. glassblower #3 made 200 jars that day and he and his team therefore gets paid X number of dollars at X cents per jar produced. Later, when glass making went to machine the numbers represented the mold or machine the jar was made from (usually 4-8 molds per machine or one to several machines per factory.) That way the plant manager could check quality control, production, etc.
Mason jars are made of soda-lime glass, have a standard 23⁄8 in (60 mm) or wide 3 in (76 mm) mouth diameter, and come in a variety of sizes including cup (half-pint), pint, quart, and half-gallon.
