 |
Glassblowing
Glassblowing is the process
of forming glass into useful shapes while the glass is in a molten,
semi-liquid state. A person who blows glass is called a glassblower, glasssmith, or gaffer.
History
While the first evidence of man-made glass occurs in
Mesopotamia
in the Late-Third/Early-Second Millennium B.C., the actual "blowing" of
glass using a tube did not occur until sometime in the First century BC
in Roman Syria.
This advancement transformed the material's usefulness from a
time-consuming process in which the medium was hot-formed around rough
cores of mud and dung into a mass-producible material which could be
quickly inflated into large, transparent, and leakproof vessels.
Glassblowing techniques spread throughout the Roman world. Venice,
particularly the island of Murano, became a centre for high quality
glass manufacture in the late medieval period.
The relatively recent "studio glass movement" began in 1962 when Harvey Littleton, a ceramics professor, and Dominick Labino, a chemist and engineer, held two workshops at the Toledo Museum of Art,
during which they began experimenting with melting glass in a small
furnace and creating blown glass art. Thus Littleton and Labino are
credited with being the first to make molten glass available to artists
working in private studios. This approach to glassblowing blossomed
into a worldwide movement, producing such flamboyant and prolific
artists as Dale Chihuly, Dante Marioni, Fritz Driesbach and Marvin Lipofsky. Lino Tagliapietra
was the first Murano-trained artist to leave and spread his knowledge
in the United States. In 1971, Dale Chihuly began the Pilchuck Glass
School near Stanwood, Washington. The Pilchuck School of Glass became the source of a great deal of the current American Studio Glass movement, and continues as such today.
In addition to glassblowing as an art, many individuals pursue
glassblowing as a hobby. In fact, it is one of the fastest growing
hobbies in North America.
Process
Traditionally, the glass was melted in furnaces from the raw ingredients of sand, limestone, soda ash, potash
and other compounds. The transformation of raw materials into glass
takes place well above 2000°F (1100°C); the glass is then left to "fine
out" (allowing the bubbles
to rise out of the mass), and then the working temperature is reduced
in the furnace to around 2000°F (1100°C). "Soda-lime" glass remains
somewhat plastic and workable, however, as low as 1000°F (550°C).
Glassblowing involves three furnaces. The first, which contains a
crucible of molten glass, is simply referred to as "the furnace." The
second is called the "Glory Hole," and is used to reheat a piece in
between steps of working with it. The final furnace is called the
"lehr" or "annealer," and is used to slowly cool the glass, over a
period of a few hours to a few days, depending on the size of the
pieces. This keeps the glass from cracking due to thermal stress.
Historically, all three furnaces were contained in one, with a set of
progressively cooler chamber for each of the three purposes. Many
glassblowing studios in Mexico and South America still employ this
method.
The major tools involved are the blowpipe, the punty (or pontil),
bench, marver, blocks, jacks, paddles, tweezers, and a variety of
shears. The tip of the blowpipe is first preheated then dipped in the
molten glass in the furnace. The molten glass is 'gathered' on to the
blowpipe in much the same way that honey is picked up on a dipper.
Then, this glass is rolled on the marver, which was traditionally a
flat slab of marble, but today is more commonly a fairly thick flat
sheet of steel. This forms a cool skin on the exterior of the molten
glass and shapes it. Then air is blown into the pipe, creating a
bubble. Then, one can gather over that bubble to create a larger piece.
The blocks are used similarly to the marver to shape and cool a piece
in the early steps of creation. The bench is a glassblower's
workstation, and has a place for the glassblower to sit, a place for
the handheld tools, and two rails that the pipe or punty rides on while
the blower works with the piece. Jacks are a tool shaped somewhat like
large tweezers with two blades. Jacks are used for forming shape later
in the creation of a piece. Paddles are flat pieces of wood or graphite
used for creating flats. Tweezers are used to pick out details or to
pull on the glass. There are two important types of shears, straight
shears and diamond shears. Straight shears are essentially bulkily
built scissors, used for making linear cuts. Diamond shears have blades
that form a diamond shape when partially open. These are used for
cutting off masses of glass. Once a piece has been blown to its
approximate final size, the bottom is finalized. Then, the piece is
transferred to a punty, and the top is finalized.
(Information courtesy of Wikipedia) |
