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The following are some of
the questions I, and my fellow glassblowers inevitably
receive from the public during glassblowing exhibitions:
 Q:
What is glass?
A: Glass is primarily melted sand, the kind you find on
the beach. Sand is composed mostly of silica crystals
(silicon dioxide -- silicon and oxygen, SiO2 -- the two
most abundant elements in the earth’s crust). The
problem is that the melting point of sand is around
3100˚ F. which is impractical for glassblowing. Adding
soda ash (sodium carbonate) lowers the melting point to
a more acceptable 1600˚ F., but unfortunately, glass
made from silica and sodium carbonate will actually
dissolve in water. So we add powdered limestone (calcium
oxide) to make the glass insoluble in water. The exact
percentages of these substances varies according to the
physical properties desired, but sand accounts for about
2/3 of the total.
Q: Is glass a liquid or a solid?
A: It is neither – or both depending on how you look at
it. It is called a liquid/solid because as it cools from
the molten state, it becomes a solid without
crystallizing. The atoms of minerals and metals, on the
other hand, line up in an orderly crystalline
arrangement as they cool. Glass atoms remain randomly
arranged in a non-crystalline (amorphous) state.
Q: How hard do you have to blow?
A : Temperature is the critical variable. If the glass
on the end of the blowpipe is too cold, you could blow
your brains out and nothing will happen. You might as
well be blowing into a brick. If it is too hot, a slight
puff might blow a hole through the glass. So, you don’t
have to blow hard if the glass is the right temperature:
not too hot, not too cold, just right.
Q: What happens if you inhale?
A: Not much, since you are inhaling the air that you
previously blew into the glass. If the glass is hot
enough, however, carefully inhaling will collapse the
sides of the bubble, creating a dimpled object. This can
produce a very nice effect.
Q: How do you get the color in a piece of blown
glass?
A: Color can be applied in various ways: by rolling a
hot gather of clear colorless glass in colored glass
powder or in chips of colored glass called frit or in
shards of colored glass. You can also begin a blown
piece with a chunk of solid color. The colored glass is
usually coated with layers of clear colorless glass,
although sometimes the color is applied to the outer
surface of a blown piece. Each method yields different
effects.
Q: How is the colored glass made that you use to
color a blown piece?
A: Metallic oxides are added to clear glass to create
colors. Almost any material can be dissolved in glass.
Blue is made by adding cobalt or copper to clear glass;
green (chromium), ruby (pure gold) – the exact formulas
are closely guarded secrets of the manufacturers.
Special glasses are also made by adding substances to
the clear glass, for example, crystal is made by adding
lead oxide.
Q: What is Pyrex?
A: Borosilicate (Pyrex) glass is made with boron oxide
in place of the soda and lime found in soft glass plus a
metal oxide such as aluminum oxide. Because the boron
oxide particles are so small, the silica is held
together more closely resulting in a much stronger
glass.
Q: Does the color go all the way through a piece of
glass?
A: Rarely. It is usually sandwiched between layers of
clear colorless glass. If you were to break say, a blue
vase and view the edge of one of the shards, you would
see a very narrow band of blue color – perhaps the
thickness of a human hair -- in the middle of clear
glass.
Q: If glass is primarily made of sand, what happens
when lightening strikes the beach? Do you have glass or
just some hot sand?
A: Glass. If lightening strikes the beach, the heat will
melt the sand and create glass, producing what is known
as a fulgurite. Most are hollow tubes, many with
branches projecting out from along the tube, much like a
dead tree. They range from a few inches to as long as 15
feet. You can see some in the final scenes of the movie
"Sweet Home Alabama" where some large fulgurites are on
display in an art gallery.
Q: Who first discovered glass?
A: Stone-age man used natural obsidian, a glass formed
by the heat and pressure of volcanoes, for tools. The
earliest man-made glass objects, glass beads and glazes
on ceramic pots and vases dates back to about 3500BC in
Egypt and Mesopotamia (Iraq). The oldest glass vases
date back to the 16th century BC in Mesopotamia. The
earliest blown glass dates back to about the time of
Christ in Syria. About that time the Romans began using
molds for blown glass. Glassblowing spread throughout
the Roman Empire, and gradually different areas
developed distinct characteristics. During the Middle
ages, Venice assumed the role as the world’s glassmaking
center. Because of the danger of fire and to protect
glassmaking skills and secrets, in 1291 city authorities
transferred all glassmaking to the island of Murano
where several thousand glassmakers lived and worked. (Murano
is still an exciting place to visit today.) In the 14th
century, another Italian glass center, near Genoa, began
to spread glassmaking skills to other countries in
Europe, so that today many European countries (Sweden,
UK, Germany, France, Eastern Europe, etc) all boast of
glassmaking industries. Some European glassmakers
immigrated to the US in the early days of our nation’s
history. The US developed a thriving glass industry, and
today the US is given credit for establishing the
studio, or artistic, glass movement, beginning in the
1930’s.
Q: Why is shipping so expensive?
A: Glass has to be specially wrapped with lots of extra
padding to ensure safe arrival. Shipping costs are in
part due to the size of the box.
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