Il crystal glass, commonly called crystal, is a type of glass in which lead replaces the football contained in a typical glass of potassium carbonate.
Lead crystal is highly sought after for its decorative properties.
It owes its discovery in 1674 to the English George Ravenscroft.
George Ravenscroft - Own work
This technique involving the addition of lead oxide (in quantities between 10 and 30%) has improved the appearance of the glass and made it easier to melt using charcoal as a furnace fuel.
With the addition of lead, glass has become easier to work with, manipulate and treat.
The term lead crystal is not, technically, a precise term to describe lead glass, as amorphous solid, the glass lacks a crystal structure.
The use of the term lead crystal remains popular for historical and commercial reasons.
It is derived from the Venetian term crystal to describe the rock crystal imitated by Murano glassmakers.
This denomination has been kept up to the present day to describe decorative objects.
Lead crystal objects they were, in the past, used to store and serve drinks, but due to the health risks, this use has become rare.
An alternative material is crystal, in which they are used: barium oxide, zinc oxide or potassium oxide instead of lead oxide.
Il lead-free crystal has a refractive index similar to lead crystal, but it is lighter and has less dispersive power.
In the European Union, theproduct labeling crystal is regulated by the Directive 69 / 493 / EEC of the European Council, which defines four categories, depending on the chemical composition and properties of the material.
Only glass products containing at least the 24% lead monoxide can be defined lead crystals.
I products with less oxide lead or glass products with other metal oxides, used instead of lead oxide, they must be labeled crystal.
Source: wikipedia.it
