page_title: Lead glass
section_title: Lead crystal
hierarchical_section_title: Lead glass / Lead crystal
caption_attribution_description: glass beads
context_page_description: Lead glass, commonly called crystal, is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40% lead(II) oxide, while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. Lead glass is often desirable for a variety of uses due to its clarity.
  The term lead crystal is, technically, not an accurate term to describe lead glass, as being an amorphous solid, glass lacks a crystalline structure. The use of the term lead crystal remains popular for historical and commercial reasons. It is retained from the Venetian word cristallo to describe the rock crystal imitated by Murano glassmakers. This naming convention has been maintained to the present day to describe decorative hollow-ware.
  Lead crystal glassware was formerly used to store and serve drinks, but due to the health risks of lead, this has become rare. One alternative material is crystal glass, in which barium oxide, zinc oxide, or potassium oxide are employed instead of lead oxide.
context_section_description: 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 higher refractive index also raises the correlated dispersion, the degree to which the glass separates light into its colors, as in a prism. The increases in refractive index and dispersion significantly increase the amount of reflected light and thus the "fire" in the glass.
  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:
caption: Lead crystal beads
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