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The Properties of Glass Bottles

Glass bottles tell stories about how they came into existence. As technology advances, the properties of glass bottles change. Professionals who seek to date old glass bottles inspect them to discover clues about how they were made. By judging a glass bottle's characteristics, you can guess its date of origin and see if you are holding an antique. It is usually possible to determine the age of glass bottles to within 10 to 15 years of their production date.

Purpose
- A glass bottle can disperse its contents once or more than once; bottles may also have multiple purposes. Some antique glass bottles, known as utility bottles, were made to hold a variety of different products. The men and women of the early 19th century commonly reused their cherished bottles.
Mold Seams
- Antique, hand-blown bottles do not have mold seams; neither do bottles made in turning molds. However, old glass bottles that were made with Ricketts molds will have distinct seams. Bottles made in automatic bottle machines will have seams that reach the bottle's closure area.
Closure Types
- Glass bottles of the late 1800s with screw-in closures have interior threads. Screw-on or crown-capped vintage bottles will have exterior threads. Some glass bottles are designed to work with Hutchinson or Lightning stoppers; a bottle of this type will have prominent lips to hold the ring in place.
Lip
- A glass bottle's lip, or finish, provides evidence of the bottle-making process used to create it. Asymmetrical lip rings suggest bottle reheating and hand or tool finishing. Symmetrical bottle lips reveal that the bottle came from an automatic bottle-making process.
Color
- Color provides clues about a glass bottle's age. Bottles that look black until held up to light might be quite old. Vintage glass bottles, with iridescent hues of cobalt, aqua, amethyst or pale yellow, may be pre-World War I glass bottles.
Bases
- A glass bottle's base determines if the bottle will stand upright or not. Typically, bottles that stand up have arched or indented bases. This feature ensures that temperature changes during production do not prevent the bottle from sitting flat when it is finished. Rounded bottoms prevent some antique bottles from standing upright.
Embossing
- Many glass bottles show evidence of mold cuts or engravings that convey information. The embossing may be a decorative element, a mold identification number or the name of the company that ordered the bottles. Such markings can indicate when the bottle was made.

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