Ask the right questions about glass bottles
I have been known to say, “You get all the answers when you ask the right questions about an antique.” In graduate school, while appraising objects at a rate of 20,000 each year for the last 15 years and by working with objects in major museums, I learned which questions to ask.
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, is it mouthblown glass made by people called gaffers and mold boys before 1900 or mass-produced by an automated bottle machine introduced in the early 1900s?
Pre 1900 bottles
Mouthblown glass bottles were common from the late 1700s to about 1900. These hand-made glass bottles were 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. These hand-made bottles are made at a production rate of about 2 bottles per minute.
How is a mouthblown 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 into the bottle’s shape.
The mold boy was responsible for opening and closing the mold and for removing the completed bottle from the mold to keep the process moving along.
A snapper worked the tool which snapped the bottle off or used the pontil rod that separated the glass blower’s blow pipe from the completed bottle at the base.
Another aide took the finished bottle to an 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.
Mouthblown 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.
Post 1900 bottles
By 1903, an automatic machine called 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. Then, the machine with its 10-12 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 bottles and 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.
(Dr. Lori Verderame hosts antiques appraisal events worldwide. Bring an antique for a free appraisal by Dr. Lori at Suburban Home and Garden Show in Oaks Feb. 21 through 23. Dr. Lori is the star appraiser on Discovery channel. Visit www.DrLoriV.com, www.Facebook.com/DoctorLori, Lori Verderame on Google+ or @DrLoriV on Twitter.)