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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.
24% Lead Crystal
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.
“Lead Crystal” is made from a mixture of sand, potash
and lead oxide. Lead crystal is lead glass that has been hand or machine cut with facets. Lead oxide added to the molten
glass gives lead crystal a much higher index of refraction than normal glass, and consequently much
greater "sparkle". The presence of lead also makes the glass softer and easier to cut. Crystal can
consist of up to 33% lead, at which point it has the most sparkle. The higher lead content also makes
it much more difficult to form crystal during blowing.
The raw materials for making glass consist mainly of silica (sand).
To melt the sand to make glass, the furnace has to reach a temperature of approximately 3,600°F (1,982°C).
Because of the presence of iron in sand, glass with a greenish colour mostly results. So only sand of
exceptional purity, white sand, is sought. In Ireland, this white sand is mainly sourced in the
Wicklow mountains.
In 1676, an Englishman named George Ravenscroft discovered that by adding lead oxide to the glass
composition, a far more brilliant sparkling glass could be produced than had ever been made before.
Besides the highly refractive appearance of lead crystal, this glass is also much softer than regular
glass, due to the properties of lead. This softness makes it easier to cut.
The maximum lead content is 33%. However, 33% lead crystal requires a lot of skill in forming a shape at
the blowing stage. So, lesser percentage lead content is often used, although the same sparkle is not
achieved. Ireland though, has maintained a reputation world-wide for its skilled blowing of 33% lead
crystal
Lead crystal is a material rich in symbols :
Symbol of life, lead crystal is a reminder of the four elements, ultimate components of life : earth,
fire, wind and water.
Symbol of purity, glass has often been used as a representation of innocence and virginity. Many Italian
Renaissance paintings show virgins depicted next to glass objects through which light passes without
altering them.
Symbol of greatness , lead crystal, considered as a precious material, has often been reserved for the
elite. Beyond its symbolic meaning, lead crystal has won acclaim with its sparkle its intensity , its
transparency and its unequalled musicality
Some Common Glass and Crystal Making Techniques
PANTOGRAPH or GUILLOCHE
The pieces are dipped in wax, and then the wax is scraped away in a particular pattern. After this is
done, the glass is dipped in a mild acid. Where the wax has been scraped away, the acid burns a pattern
in the glass.
SANDBLASTING
Parts of the piece that are not to be sandblasted are covered, and then a small nozzle is used to shoot
a fine stream of silica at the piece. This technique is often used in combination with cutting.
COLOURING THE GLASS
To make colored glass, different pigments are added to the glass-mass. For example, to produce green,
copper oxide is added to the mixture. To produce blue, cobalt oxide is added. As well, it is possible
to produce black, brown, red, orange, yellow and purple glass, in a myriad of shades.
CUTTING
Although it is possible to make some cuts in sodium potassium glass, lead crystal is the material of
choice for this technique. Because of the higher refraction index of crystal, cuts in the crystal both
add to the interest and appearance of the piece, as well as making it appear very clean and bright.
MACHINE ENGRAVING
Machine engraving is used on both hand-made and automatic production pieces. This technique is used to
ensure uniformity from piece to piece.
Lead crystal, which is mouth blown in the traditional method, may from time to time have a few minor
bubbles contained within the piece. This is generally accepted as a by-product of the traditional process
and does not detract from the piece. On occasion, small, barely perceivable lines may be detected within a
piece of crystal. These represent slight variations in the density of the molten crystal, which remain
after the crystal has cooled. These lines are called cords and are also considered a by-product of the
traditional process.
It should be noted that each piece of true hand cut lead crystal is a unique product of the individual
artisan or artisans who have produced it. For example within a set of stemware of the same pattern there
may be very slight variations in pattern size and spacing of the elements. This only serves to embellish
the charm and appreciation of such artisanship and is by no means considered a detriment. Absolute product
consistency is only achieved by fully mechanized production, not by a craftsperson.
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