| BARIUM GLASS |
When barium oxide is added to the
basic glass mixture, the result is a product of superior
clarity, strength and resiliency. Barium glass is primarily
used in the production of those stemware lines which
have a long, slender stem, or relatively thin-wall bowls. |
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| BLANK |
| An undecorated piece of glassware or crystal which will
be subjected to further processing for decorating. |
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| BLOWN GLASS |
Glass forced into shape by air-pressure,
either by hand blowing or machine blowing. This can
be done with or without the use of a mold. |
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| COLOURED CRYSTAL |
As previously mentioned, colour
is introduced into glass by the addition of various
oxides to the basic batch mixture. Gold oxide (as well
as chrome oxide) is used to produce the ruby colour
-this is the reason why ruby glass is generally more
expensive. Iron oxide produces a green colour, cobalt
oxide produces blue glass and the addition of uranium
oxide will produce an amber or yellow colour. It should
be noted that generally, colour is found in non-lead
crystal products, but may be used in glass which covers
full lead crystal (i.e. Cased Crystal) -two layers blown
on top of each other, i.e. top layer - non-lead crystal;
underneath layer -clear, over 2470 lead crystal -item
is then cut through bottom layers as a means of decoration. |
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| CRYSTAL |
A much abused term which in the
trade, simply refers to a clear colourless glass. The
general materials used to produce crystal are fine silica
sand, potash, and cullet (broken pieces of glass which
are essential for the batch mixture). Other materials
can be added to the basic batch mixture, such as oxides,
i.e. lead oxide, gold oxide, etc. |
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| CUTTING AND ENGRAVING |
Cutting and engraving on glass
or crystal are two completely separate techniques of
decorating glassware. The easiest way to distinguish
between the two techniques is that cutting is a "wet
process", while engraving is a relatively "dry
process". A continuous stream of water flows over
the diamond corborundum wheel which generally produces
a deep cut. By using different diameters and thicknesses
of wheels, the master cutter can achieve various degrees
of cuts on an item. The water is used to wash away the
tiny particles of glass being removed during the cutting
process. Engraving is done generally with the use of
a small copper wheel which produces a "shallow
cutting" into the surface of the product. A small
amount of abrasive fluid (not water) is used in order
for the wheel to move more smoothly over the surface
and scratch the design into the piece. |
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| GUILLOCHE |
This is an identical procedure
to panto, but there is only one needle used producing
simple geometric patterns which are continuous. |
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| LEAD CRYSTAL |
When lead oxide is added to the
basic glass mixture, "lead crystal" is produced.
The amount of lead oxide added, determines the classification
of the crystal, as well as the strength of the crystal.
Semi-lead crystal (crystalline) contains approximately
8-10% lead oxide, while the term "full lead crystal'
is generally conceded to contain a minimum of 24% lead
oxide. Lead oxide was initially introduced into crystal
by the English approximately 250 years ago, due to the
fact that it has a low melting temperature (1000-1200
degrees Celsius). Lead oxide also adds a brilliance
to the product when cut. It should also be noted that
the most important reason for using lead oxide, is to
soften the glass and, therefore, facilitate cutting
and engraving on the item as a means of decoration.
There are obviously disadvantages of having a softer
glass product, i.e. more unstable during temperature
changes; if softer, then tends to chip or scratch much
easier. |
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| MOLDS |
Both wooden and cast iron molds
are used in the production of crystal. Although, the
wooden molds are produced of hardwoods (Cherry and Beechwood),
they must be replaced more often as they burn-out after
a time despite being immersed in water. |
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| PANTOGRAPH |
By taking a basic clear glass and
dipping it into a mixture of paraffin and bee's wax,
the glass becomes covered in wax. Then the glass is
placed on a machine which has four needles surrounding
the glass. An operator traces a stencil which is hooked
to the machine and wherever the operator traces, so
too, do the four needles and thus they remove the wax
leaving a design. The glass is then taken and placed
in an acid solution for anywhere from 7 to 40 minutes
-depending on the size of the piece and acid concentration.
In this process only the areas uncovered by wax are
eaten away (the design area) and the wax is removed
later by hot water, to be reused. |
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| PRESSED AND OVER CUT |
This refers to an item, generally
produced in lead crystal, that has had its blank and
possibly some of the major cuts pressed. The piece,
however, must be finished with fine hand-cutting by
a master cutter in the same manner as a completely hand-blown
item. |
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