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 Blown
glass is created by a layering process; that is, a
building up of layers of glass from the inside out. The
blowpipe is dipped into a crucible of molten glass (at
about 2200° F.) and a small amount glass is ‘gathered’
onto the blowpipe. The glass is prevented from falling
off the pipe by constantly turning the pipe to counter
the force of gravity. The semi-liquid/solid glass is
shaped into a spherical form with the aid of wet wooden
tools called blocks. The glassblower blows a small air
bubble in the gather, which he will expand at various
stages of the production process. The glass cools
quickly to the point at which it no longer moves. It can
then be dipped back into the crucible for a second layer
(gather). This process can be repeated as many times as
necessary to build up the required mass.
At any point in the layering process color can be added
to the piece using powdered glass, small chips of
colored glass, called frit, or shards. Color is
generally sandwiched between layers of clear
glass. However, sometimes color is applied to the outer
surface, or a solid chunk of colored glass is used in
place of the first gather from the crucible. Each
approach yields a different effect.
The piece must be repeatedly re-heated in the glory
hole which is kept at 2400˚ F. to keep the glass
pliable. In most cases, the piece is transferred from
the blowpipe to a solid steel rod called a puntil
(pronounced - punty). This is done by sticking the end
of the puntil onto the bottom of the piece with the aid
of a small amount of hot glass gathered onto the end of
the rod. The piece is then broken off the end of the
blowpipe thus exposing what will be the top of the
piece. The opening or top of the piece can then be
re-heated and trimmed and shaped as necessary, using
tools especially designed for that purpose.
After the piece is finished it is literally knocked off
the puntil and placed into an annealing oven at about
900 degrees F. and slowly cooled to room temperature,
usually overnight to relieve any stress in the glass. If
the piece were allowed to cool without this annealing
process, it would shatter. |
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