Bottles were made
The process of making bottles has evolved over the
years. Understanding the time line, evolution and
associated tooling marks allows for easy identification
of antique bottles. Glass is basically made from a
mixture of sand, soda, lime and heat. The earliest Free
Blown glass was usually dark green or more commonly
called Black Glass. These European style bottles derived
their color from iron which was mixed into the raw
materials. Bottles have been made in America since the
earliest settlers in Jamestown in 1608. These bottles
were hand blown, just like European Black Glass and the
earliest Roman glass which dates back to the 1st century
B.C. The early glasshouse in Jamestown was not very
successful and only produced bottles for a few years.
The first truly successful glasshouse in America opened
in New Jersey in 1739. Since that time bottle
manufacturing has evolved steadily.
We can use this evolution and the tell tale marks
associated with each new method to estimate the age of
bottles we find. The first bottles ever made were hand
blown without a mold. This process is called Free Blown.
Free blown bottles were made one at a time in a very
time consuming fashion. Because they were hand blown
without a mold have no mold seam marks. These early
bottles may however have other manufacturing marks that
can lead us to identifying them. In order to remove Free
Blown bottles from the blowpipe, a separate metal rod
topped with hot glass was attached to the bottles base.
When this rod was later broken off it left a distinct
pontil mark. In order to produce more uniform shapes an
ever evolving variety of molds were created. Bottles
hand blown in a mold are called Blown in Mold (BIM). The
earliest of these was the dip mold which was used to
create a bottles body and left almost no identifiable
mold seam markings on the bottle. Wood molds were used
before cast iron molds were developed in the mid 1800’s.
The wood was kept moistened in an effort to prevent the
hot molten glass from charring the wood but still
typically only lasted for 1000 casting. Some bottles
made in wood molds will actually show the wood whittle
marks. Hinged molds of various height and design were
later developed which all left identifiable seam marks.
Most of these were two part molds but some used three
part molds and others had distinctive bottom hinge seams
all of which can be helpful in the identification
process. The majority of these blown-in-mold (BIM)
bottles were finished with an applied top. Basically a
blob of glass was applied after the body of the bottle
was blown in the mold. An additional innovation was
special tooling which allowed the applied tops to be
sculptured to more uniform designs.
These tops are
called hand tooled or hand finished tops. The basic
evolution of glass making and development of molds is
important to remember because it allows us to understand
why some older bottles’ seam marks end before the top
and other younger bottles which were made in full height
molds have side seams which run to the top or even over
the lip. For most blown in a mold bottles the rule is
that the side seam can often be used as a gauge to the
bottles age “ the further down the side the seam ends,
the older the bottle”
During the proliferation of Mold Blown bottles Slug
Plates were developed. A Slug Plate is a reverse
embossed metal plate which is inserted into a two or
three piece mold. They allowed smaller manufacturers and
local businesses to emboss their own logo on a plate
which would be interchanged in a standard bottle mold.
The result would be individualized product branding
without the expense of creating a unique mold.
In the early 1900s Michael Owens invented the automatic
bottle machine. This invention revolutionized the
industry. The 1903 version of his machine could produce
13,000 bottles per day. By 1909 improvements allowed the
machine to make even small thin glass medicine bottles.
One of these machines could make over 30,000 per day. By
1917 an automatic machine could spit out over 60,000
bottles per day, which made bottles much more affordable
to the masses. All bottles made by machine are referred
to as Automatic Bottle Machine or ABM.
The most common color of early glass made in the United
States was green or light blue in variations of shades.
This early glass is called Aqua glass. Clear glass was
much more expensive to produce because glass blowers had
to pay for more purified materials. It was later learned
that a variety of compounds could be added to the basic
mix to obtain other colors such as amber, cobalt blues
Around the turn of the century, the typical color of
glass used for bottles changed from aqua to clear. Fewer
bottles were being embossed with unique individual
manufacturers logos and by the late 1930's painted label
bottles became more cost effective to produce. Bottles
lost their individuality as technology improved.
Knowing the techniques of glassblowing, including how to
identify free blown, mold blown and automatic machine
made bottles and the unique manufacturing marks each
process leaves on the finished product is the key to
estimate a bottles age. Please refer to this texts
bottle mold seam and time line diagrams for a visual
reference of each style mold and associated identifying