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
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