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 Casting And Cutting
CASTING
One of the earliest methods used to make vessels, and decorative
objects may have been the technique described below. Compare this method of
glass making with CORE FORMING for speed of manufacture. Compare both of
these methods with GLASSBLOWING methods.
Materials were mixed together and heated just to the point of fusing
together. This composite, nearly glass-like, was cooled, ground into a
powder, and may have been poured into a clay mold similar to that
illustrated here. The mold was placed in the furnace to "e;soak"e; in the heat
until the powder melted into a viscous mass. As it melted together it
would "e;slump"e; down in the mold. More powder had to be introduced at the
top. This process continued until the mold was full and all the powder
melted. The hot mold and its contents were then removed from the furnace.
Several hours later, when the mold and glass had cooled, the mold was
opened and the solid glass bottle-shaped object was removed. To be
useful as a vessel, the solid glass had to be drilled-out and possibly
turned on a lathe to grind and polish the outside surface.
Though many ancient glass containers have been found, ancient glass
sculpture is vary rare. The portrait of Amenhotep II, who preceded
Tutankhamun (King "e;Tut"e;) by about sixty years as ruler of Egypt, is the
earliest glass portrait known.
Cast and cut in dark blue glass, one or two microns' thickness of the
sculpture's surface changed to a light brown crust during its long
burial.
The object was probably modeled in wax. The model was coated with clay
and heated. While the clay hardened, the wax melted and ran out,
leaving a cavity of the same shape and size as the original model. This
cavity was used as the mold.
Jewelry and furniture inlays were often cast in open, simple molds and
were complete once they were removed. All that these objects may have
required was some polishing.
The generic name for a wide variety of techniques used to form glass in
a mold.
Core forming:
The technique of forming a vessel by trailing or gathering molten glass
around a core supported by a rod. After forming, the object is removed
from the rod and annealed. After annealing, the core is removed by
scraping.
Cutting:
The technique whereby glass is removed from the surface of an object by
grinding it with a rotating wheel made of stone, wood, or metal, and an
abrasive suspended in liquid. See also copper-wheel engraving, carving,
and wheel engraving.
CUTTING
Shaped pieces of sandstone or sand consolidated with gypsum were often
used as polishers and abrading tools to work stone in ancient Egypt.
Similar tools used by stone and metal craftsmen could have been used to
cut, grind, and polish glass.
Shaped pieces of sandstone or sand consolidated with gypsum were often
used as polishers and abrading tools to work stone in ancient Egypt.
Similar tools used by stone and metal craftsmen could have been used to
cut, grind, and polish glass.
By 4th - 1st century B.C. lathes were commonly used to hold the object
to be cut in a fixed upright position. These were reciprocating lathes.
They rewound after a cutting turn, instead of turning continuously in
one direction as modern lathes do. Tools were pressed against the
turning glass, eventually grinding it to shape. Lathes resembled and probably
performed about the same as ancient pottery wheels.
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