Lead Glass - Lead Crystal

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