Lead in Crystal Glass

If soda is replaced by potassium carbonate in glass manufacture and lead oxide is added, the light refraction properties of the glass are improved. The whole crystal glass contains at least 24% lead oxide, while the semi-crystal glass has at least 10% in all of lead, potassium and zinc oxides. Some characteristic physical properties of the different glass types are shown in Table 43.5. 

Lead glass has been appreciated as crystal glass due to its refraction, brightness and weight. The glass is also used for optical applications, as well as for cathode ray tubes 

Class type Density g/cnP Refractive index Coefficient of thermal expansion 

For whole crystal glass no alternative seems to be possible as the international quality systems specify a lead oxide content of 24% or more. Until these specifications are changed, the manufacture of glass with high lead levels will continue. 

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