Important stages in the history of glass: the search for crystal

The search for a pure material, limpid and colourless like rock crystal (a kind of quartz) was to be the great preoccupation of European glassmaking from the 15th to 18th centuries.

The term crystal referred initially, from the 15th century, to the Venetian soda-lime glass whose purity was essentially due to the superior quality of raw materials and the use of manganese as a decolorant. It later referred to a potassium-silicate material that the Bohemian glassmakers were to perfect in around 1680.

But none of these types of glass that did not contain lead oxide could be called true crystal today : according to the EU norms, crystal should contain at least 24% lead oxide.
It was created in England in around 1676 when George Ravencroft discovered that adding litharge and later on lead minium into the mix of raw materials made for an easier fusion and a more stable glass. This material was more resonant, heavier and shinier than normal glass and would become a must all production of the luxury items.