Lead oxide added to the molten glass gives lead crystal a much higher index of refraction than normal glass, and consequently much greater "sparkle" by increasing specular reflection and the range of angles of total internal reflection. Ordinary glass has a refractive index of n = 1.5; the addition of lead produces an index of refraction of up to 1.7. This heightened refractive index also raises the correlating index of dispersion, which measures the degree to which a medium separates light into its component spectra, as in a prism. This increase in refractive index from 1.5 to 1.7 significantly increases the amount of light reflected (by a factor of 1.68 for light reflecting in the normal direction; see Fresnel equations).
In cut glass, which has been hand- or machine-cut with facets, the presence of lead also makes the glass softer and easier to cut. Crystal can consist of up to 35% lead, at which point it has the most sparkle.
Makers of lead crystal objects include
| Name | Polity |
|---|---|
| Baccarat | France |
| Dartington Crystal | England |
| Arc International | France |
| Royal Brierley | England |
| Royal Leerdam Crystal | Netherlands |
| Ajka crystal | Hungary |
| Steuben Glass | United States |
| Waterford Crystal | Ireland |
| Mikasa | Japan |
| NovaScotian Crystal | Canada |
| Liuligongfang | Taiwan |
| Swarovski | Austria |
| Preciosa | Czech Republic |
Read more about this topic: Lead Glass
Famous quotes containing the words lead and/or crystal:
“Nature is unfair? So much the better, inequality is the only bearable thing, the monotony of equality can only lead us to boredom.”
—Francis Picabia (1878–1953)
“The crystal sphere of thought is as concentrical as the geological structure of the globe. As our soils and rocks lie in strata, concentric strata, so do all men’s thinkings run laterally, never vertically.”
—Ralph Waldo Emerson (1803–1882)