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What is Crystal?
Glass, Crystal & Engraving Techniques
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Glass "Ingredients"
Glass is made using three different minerals:
1. Sand (silica) - intense heat changes sand into a fragile form of glass.
2. Soda ash (sodium carbonate) - this is a powdery white material that
is added to the mixture to lower the melting temperature of the sand.
3. Limestone (calcium carbonate) - this is added to make the glass stronger.
The raw materials are melted together in a furnace at a temperature of 1600 celcius. This is the same temperature as a jet engine!
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What makes Crystal?
The inclusion of at least 24% lead oxide in the composition is required
by law for crystal to be called full lead crystal. The lead lends
brilliance and weight to the product. Crystal without lead is still
crystal, i.e. clear glass, however, it is more commonly perceived as
"glass". The lead also make the crystal softer and more conducive to
cutting. This is why the lead crystal is cut and for the most part, the
unleaded crystal is not cut.
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Optical Crystal
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Optical Crystal, as clear and as flawless as used in binoculars and camera lenses, represents the ultimate
expression of excellence. Optical Crystal is manufactured in large sheets up to 3" thick, and while still
molten, is subjected to tremendous pressure to ensure no bubbles, flow lines or other distortions.
Optical Crystal is 100% Lead Free and extremely hard. It is this hardness that provides the basis for the
brilliant cuts and bevels, as well as the ultra high polished surfaces. Each piece of Optical Crystal is hand
polished and beveled. What an ideal way to recognize achievement and express appreciation.
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Black Optical Crystal
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Black crystal is produced with special additives (Fe2O3, CuO,
MnO2, CO2O3) that change the color to black. Black crystal posses
almost the same physical qualities as lead free clear optical crystal.
However it does not allow light transmission. Black crystal is by far
superior in quality to black color glass, it has no bubbles or swirl
marks and it's surface is perfectly smooth and flawless. When black
crystal is combined with chrome plated metals, it transforms an award
to a unique expression of modern design.
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Starfire Glass
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Starfire Clear Glass is a lead free, low iron product that represents the very
best in glass trophies although not clear enough to be called
“crystal”. A slight blue tint is evident in the most-clear product.
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24% Lead Crystal
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Most fine crystal contains lead oxide. 24% is the optimum percentage for
color, weight and hardness, while still ensuring clarity, sparkle and
brilliance.
24% Lead Crystal, with its exceptionally high perceived value, has been
sought after and treasured for generations, and remains a status symbol
even today.
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Glass and Crystal Techniques
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"Handcut"
means the glass item is held against a spinning stone to "cut" the
design. It is truly artistic workmanship at its best!. Crystal without
lead is not any less valuable than full lead crystal particularly when
it is thick and heavy and finely designed. In fact, clear uncut crystal
has to be particularly fine quality because the flaws can not be hidden
by the cuts.
Engraving
The process of cutting into the surface of an annealed glass object
either by holding it against a rotating copper wheel fed with an
abrasive or by scratching it, usually with a diamond.
Carving
The removal of glass from the surface of an object by means of hand-held tools.
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 as the cutter holds the
object against the upper, or top, side of the rotating wheel. See also
copper-wheel engraving, carving, and wheel engraving.
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History
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Little is known about the first attempts to make glass. The Roman
historian Pliny attributed it to Phoenician sailors. He recounted how
they landed on a beach, propped a cooking pot on some blocks of
natron(an alkali; a natural occurring evaporate form of soda found
around the shores of lakes in the Wadi Natroun, Egypt--used in the
mummification process in ancient Egypt ) they were carrying as cargo,
and made a fire over which to cook a meal. To their surprise, the sand
beneath the fire melted and ran in a liquid stream that later cooled
and hardened into glass. That said, no one really knows how glass came
to be made. It is thought that the ability to make glass developed over
a long period of time from experiments with a mixture of silica-sand
(ground quartz pebbles) and an alkali binder fused on the surface. The
material called faience had been used for well over a thousand years to
make small decorative objects such as beads and amulets. Although it
existed as an ignored, accidental byproduct of copper smelting, true
glass probably was first made in western Asia, perhaps Mesopotamia, at
least 40 centuries ago. Perhaps early development began with potters
firing their wares. Could the first glass have been colorful, hard,
shiny decoration fused to a clay pot's surface in the heat of the
furnace? No one knows. It was later discovered that if the material
were thick enough, it would stand by itself. Pieces of solid glass
could then be ground to shape by grinding it with stones, or sand and
water, to produce vessels.
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Glassblowing Discovery
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Until about 50 B.C. glass objects could only be made slowly. One bottle
could take several days to make by casting, core forming, or cutting
techniques. Because it was difficult and time-consuming to make, glass
was a luxury item as rare as gold or precious stones. That situation
quickly changed with the discovery of glass blowing. Roman people,
probably in Phoenicia(mostly modern Lebanon) discovered that an object
could be formed by gathering molten glass on the end of a hollow
blowing pipe, and inflating it like a bubble. It could be blown into a
hollow mold to form it or freely shaped with simple tools on the end of
the blow pipe. For the first time, a worker could mass-produce dozens
of objects a day with glassblowing techniques. Most, but not all of
these products became common and inexpensive. Soon anyone was able to
own glass.
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The information above has been compiled from the resources provided by the following:
Corning Museum of Glass
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