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How to Date Glass Jars

Glass jars have been used since the 19th century to store and preserve food. Original glass jars were sealed with wax to keep food fresh, but the wax was eventually replaced with the mason jar style that many people still use today. The tight top and seal on the glass jars keep food fresh, and the clear glass allow you to see the ingredients, food and preserves that you want to store in the glass jars. There are some clues that can help you disclose when antique glass jars were made.

Things You'll Need

Glass jar
Date indicators

Instructions

- 1
  Look for a ring of glass or a dark indention on the base of the jar. If the jar has this characteristic, known as a pontil scar, it shows that it may have been held with a pontil rod to protect the glassblower from the hot glass while the jar was being made. These scars indicate that the jar was probably made before 1855.
- 2
  Look for indications of mold seams on the glass jar. The first glass jars were made without a mold, so if you do not find a mold seam, the glass jar may have been made before 1915. After this date, glass jars that were made with machines were given mold seams running from the bottom of the glass jar to the top of the glass jar.
- 3
  Look for small scars or abrasions on the bottom of your glass jar. If the glass jar was made after the 1930s, it was most likely made by a machine rather than by hand and will have more uniform marks. The rougher the glass and the seams around it, the more likely it was made by hand and could date before the 1930s.

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