Precision machine cut and polished full lead crystal. This type of crystal has at least 30 per cent lead content which gives it color refraction and beautiful sparkle. This grade is the highest grade available in crystal. Beware of claims such as “100% crystal” by some retailers. Crystal can only have upto 35% lead content.
Full Lead crystal is lead glass that has been machine-cut with facets. 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, whereas the addition of lead produces a range up to 1.7. This heightened RI 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. 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. The higher lead content also makes it much more difficult to form crystal during manufacturing.