Lead Crystal Spiral Vase by Ann Robinson

• Lead Crystal - The first clear glass, called cristallo was invented during the 15th century in Venice. Prior to this the glass had a slight yellow or greenish colour as a result of iron ore impurities with the glass. 'Cristallo' was heavily exported .
  
  In 1675, while attempting to counter the Venetian dominance of the glass market, British glassmaker George Ravenscroft invented lead glass, by adding lead oxide to to replace the calcium content in glass.
  
  The new glass he created was quicker to melt, and stayed moulten longer, making it easier to work. More importantly, it had a higher refractive index, adding to its brilliance and beauty, especially when embellished with wheel cut decoration.
  
  Lead crystal, is variety of lead glass, with a higher percentage of lead oxide than lead glass.
  
  Ravenscroft's patent on lead crystal expired in 1681, and more glass makers were able to take advantage of his invention. The expansion in production resulted in England to overtaking Venice as the centre of the glass industry in the eighteenth and nineteenth centuries.

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• Robinson, Ann - glass makers 53