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Glass Making in Europe
After the decline of the Roman Empire in the 4th & 5th centuries AD,
the craft of glass making waned in Europe. The industry continued to
thrive in Iran, Iraq & Egypt.
In Europe, there was a limited revival of glass making in the early
12th Century, with the development of stained glass windows for cathedrals
& monasteries.
A flourishing glass industry did not develop in Europe until the end of
the 13th Century, when Venice became a major glass making center. They
may have picked up their glass making techniques through their contacts
with the near East countries during the Crusades. The Venetian provided
the link between the ancient & modern glass making arts. Venetian glass
was noted for its brilliance & for its light, imaginative forms.
So by the 15th Century, Venice had become the major producer of
glassware in Europe. So highly esteemed were the Venetian glass makers, that
they were forbidden to leave the Island of Murano, lest their precious
trade secrets be imparted to others.
However, it was to be another 2 centuries later that in 1676, an
Englishman named George Ravenscroft made a discovery, that by adding lead to
the glass that a far more brilliant sparkle was achieved.
The Discovery of Lead Crystal
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. Lead crystal
has now been born.
Besides the highly refractive appearance of lead crystal, this newly
discovered glass was also much softer than regular glass, due to the
properties of lead. This new softness made 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.
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