Among the many features and attributes which can be ascribed to Colle di Val d'Elsa, that which is most dear to local people is the title 'Città del Cristallo' ('Home of Lead-Glass Crystal').
Since 1331, glass production, which evolved into lead-crystal production in the 20th century, has been one of the most typical features of the town, which over the centuries, for this reason, has been called the 'Bohemia of Italy', and is now the Città del Cristallo.
All this is promoted by the Cristallo di Colle di Val d'Elsa consortium, a body which represents all the firms working in the sector, which represent 95% of Italy’s entire output of lead crystal, and 14% of global production.
The aim of the Cristallo di Colle di Val d'Elsa consortium is above all to recognize, and protect, lead-crystal glass as a material, and also its production and processing at whatever level within the Colle di Val d'Elsa area.

The main difference between glass and lead-crystal is the presence of Lead Oxide.
The presence of this oxide gives the glass certain characteristics which make it particularly interesting, since the lead leads to a marked increase in the density of the glass, and thus in its refractive index.
In this way the glass comes close to the optical properties of diamonds: the incoming light is refracted to a greater degree than with normal glass, thereby giving the effect of great brilliance that is typical of lead glass.
The effect increases with an incresce in the content of Lead Oxide, but only glass which contains at least 24% lead oxide by weight has the legal right to be called 'lead-crystal glass'.

  Only skilful adjustments in the composition of the glass, by specialized chemists, working side by side with master glass-makers, make the lead glass clear, transparent, brilliant, stable, and worthy of the name lead-crystal.
In order to find out all the history and the features of lead crystal, consult the official site of the Cristallo di Colle di Val d'Elsa consortium.