For those of you who don’t know how to tell an old bottle from a new one or a valuable bottle from a cheap one, I am going to share some tips.
First of all, you have to identify the bottle. You can’t do this unless you understand how bottles were made throughout history. Some early glass was blown in the famous glass furnaces of Venice, Italy, on the island of Murano. Murano glass has a long history dating back to the 1200s.
If you want to learn about your glass piece, ask yourself, was it made by mouth-blown glass makers — called gaffers and mold boys — before 1900 or mass-produced by an automated bottle machine introduced in the early 1900s?
Mouth-blown glass bottles were common from the late 1700s to about 1900 and formed in a mold. There is not the same uniformity found in these bottles as there are in machine-made bottles. The lips are not always straight, the color may not be consistent throughout, the glass may look thicker overall. Hand-made bottles are made at a production rate of about two bottles per minute.
How is a mouth-blown glass bottle made?
A glass blower would position a hunk of glass on the end of a blow pipe inside a mold. He would expand the hot glass by blowing into the blow pipe. The mold would be filled with the blown glass and impressed with embossed lettering or a picture.
The mold boy was responsible for opening and closing the mold and removing the completed bottle from the mold to keep the process moving along. A snapper worked the tool that snapped off the bottle or used a pontil rod that separated the glass blower’s blow pipe from the completed bottle at the base. Another aide took the finished bottle to the area where the bottle would be allowed to anneal, or cool off.
Another important job was that of the furnace or shop workers, who kept the furnaces running.
Mouth-blown bottles could come out differently even if they were blown on the same day by the same glass blower. It is the issue of hand-craftsmanship versus machine-production methods. These variations and surprises are what make glass collecting so fun.
Most 19th-century blown-glass bottle-making sites were called glass houses, glass works or glass shops. Some famous glass houses were Sandwich Glass, on Cape Cod, Mass.; and the San Francisco and Pacific Glass Works in the San Francisco Bay area.
By 1903, the Owen automatic bottle machine was introduced to make glass bottles. By 1915, the majority of bottles were made by machines to form the bottle. One person could run the machine, which was positioned over a large vat of glass.
The machine — with its 10 to 12 heads and two molds per head — would rotate. It would pick up the glass, deposit it into a two-mold process and blow the glass bottle using pressurized air.
The most common machine-made bottles are those with applied color labels on them, like soda or milk bottles. These are mechanically made with uniform bottles. They were mass-produced at a rate of about 600 bottles per minute.
Machine-made glass bottles can have bubbles in the glass. Don’t think that just because your glass bottle has bubbles in it that it is an old and valuable mouth-blown glass bottle. It may not be.
Knowing how an object is made will help you to identify the bottle and pinpoint its age and origin. With glass bottles, look for mold seams and other distinguishing factors.