Page 37 - Curriculum Visions Dynamic Book

Crystal glass
Gradually the Venetians learned how to make
a form of crystal glass that has a sparkling clear
quality. It was called cristallo. Like crystal glass
made later elsewhere, it was produced by using
purer ingredients that had far less colour and so did
not have to be decolourized. A potash-lime glass was particularly clear. It became known as Bohemian crystal after the region of central Europe where it was developed.
The next development took place in London in
1674, when lead oxide was added to the mix. George Ravenscroft produced lead crystal glass this way, sparklingly clear glass still in use today. Lead glass is so sparkling because it has a very high refractive index. The advantage of lead crystal glass was that it was softer than soda lime glass and so could more easily be cut (to make cut glass, which sparkles in light) and also engraved. Lead
glass is also heavier than soda lime glass
and gives a more substantial feel. It has been used for fine
table glass ever since.
(Left and above) Crystal
glass was first made with pure ingredients, but a sparkling quality was provided through the use of lead in the glassmaking. This is a candle holder made in America in about 1830.
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