Glass
casting is one of man's oldest art forms. Archeologists
have found Mesopotamian glass beads dating
back to 2500 B.C. and the Egyptians molded
and twisted glass in its hot, liquid state
calling it "stone of the kind that flows." In
63 B.C. the Romans conquered the Syro-Palestine
area bringing glassmakers to Rome. Soon after
the word "vitrum," meaning glass,
entered the Latin language. In ancient times,
the mold was filled with sands that contained
impurities that gave the glass color.
Even
with today's technology, the glass casting
process can be quite arduous. From a creative
standpoint, however, the drawn out process
provides the artist opportunity to focus on
sculpting, coloring and cold-working (polishing,
etc) separately. The aesthetic range seems
limitless when the artist also has access to
a wide color palate that also ranges from transparent
to opaque. The great potential for beauty combined
with the great difficultly in actually achieving
it has made glass art one of the world's most
respected forms of art.
The
glass casting process begins with sculpting
a model, usually out of clay or wax. A plaster
mixture is made into a slurry and poured over
the original wax sculpture to make a refractory
negative. Once the plaster hardens, the wax
is melted out, and an empty mold is left. The
wax is said to be "lost" and hence
it is referred to as the "lost wax technique".
When sculpting with clay, there are a few extra
steps in the mold-making, due to the fact that
it does not melt���but we must leave something
to the imagination!
By
the early 20th century, glass casting had evolved
into the French style of pate-de-verre (meaning "paste
of glass") with French masters such as
Francis-Gabriel Decorchement, Amalric Walter,
and Argy Rousseau. Pate-de-verre was often
referred to as "the phantom technique" during
the art nouveau period, because elements of
the technique were kept secret from new or
competing artists.
Pate-de-verre involves applying powdered glass
of different colors into the mold, as if it
were paint. The different color powders fill
in the deepest relief of the mold first, so
the "painting" is done in layers.
If done correctly, no additional interior mold
is needed to hold the glass in its place. When
the piece fires, (around 1400*F) the particles
melt and bond with each other creating a frosted,
or nearly opaque glass that is rich in color
and texture. Some air bubbles between glass
particles are usually visible. The highest
quality pate-de-verre is very thin, semi-transparent,
and has a fire-polished interior surface due
to the glass particles fusing without contacting
a plaster interior. Pate-de-verre is widely
considered one of the least forgiving, yet
most rewarding, glass techniques. As such there
are only a few people alive who can execute
the technique at a quality comparable to the
Art Nouveau masters.
The
pate-de-crystal technique differs from pate-de-verre
in particle size and composition of glass.
In pate-de-crystal, the mold is filled with
different color pieces of leaded crystal that
range in size from fine particles to pebbles
to golf balls. Color application may be random
and flowing, or it may be controlled, but it
is usually not as precise as pate-de-verre.
Using larger chunks of glass increases transparency,
and the highly leaded crystal gives rise to
a beautiful sparkling finish not found in other
forms of glass art. Pate-de-crystal pieces
may fire up to 1700*F.
In both pate-de-crystal and pate-de-verre,
the annealing (or cooling) phase is slow, and
monitored by the kiln's computer to make sure
that the glass equalizes at a consistent temperature
so as to prevent cracking. The thicker the
crystal, the slower it must anneal. Once the
piece has reached room temperature, it is submerged
in water to dissolve the plaster mold, and
the cold-working process begins.
"Cold-working" refers to any work
done to the glass once removed from the kiln.
First, any rough edges of the glass are ground
with diamond pads or a lathe. Then polishing
with various abrasives is often needed to get
the highest sparkle, or a glass piece may be
sandblasted to give it a frosted or etched
appearance. Some HibriGlass pieces are gold
or silver leafed from behind to reflect light
back through the glass, eliminating shadows
and adding to the richness of color. We may
also use metal coatings and acid patinas to
obtain rough weathered looks in contrast to
the sparkling shine.
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