Lead glass
Lead glass, also known as lead crystal, is a type of glass that has lead in it. Normal glass has calcium oxide in it, while lead glass changes the calcium oxide with lead(II) oxide. It looks nice because the lead is very large and heavy and changes how the glass looks. Lead glass rings when tapped while ordinary glass does not. This glass can absorb some X-rays. It is very insulating.
It contains between 18 to 40% of lead (II) oxide by weight. Any glass that contains at least 24% PbO by weight is referred to as "lead crystal". Any glass that contains less than 24% PbO by weight is referred to as "crystal glass". Lead glass has a chemical composition of silicon and lead oxides, with other elements added to get colours or properties.
Lead glass is also known as X-ray glass or radiation shielding glass as one of its major applications is in the absorbance of high energy radiation while maintaining optical transparency. The presence and quantity of PbO are what determines some of lead glass' most important optical and physical properties.
Applications of lead glass
The properties of lead glass make it useful for many applications. Here are a few examples:
In the medical and research fields where visibility is required during procedures or experiments that involve radiation, lead glass can achieve the same radiation attenuation as the surrounding walls or barriers while allowing visibility to the operator. A typical example is the viewing window of an X-ray room or a laboratory experimenting with radioactive materials.
The high refractive index of lead glass is useful for the production of lenses as thinner lenses can be crafted to achieve similar focal lengths to ordinary ophthalmic glass. Lead glass is thus used for special medical glasses, binoculars, microscopes and telescopes.
Digital projectors use lead glass because it has a high level of transmission over short wavelengths, which is typical of projector laser beams. Further, the temperature rise caused by the light source does not distort the image projected by lead glass because it has a lower thermal conductivity than lead-free glass.
It is useful in instruments that operate in the near-ultraviolet region and the near-infrared region as in bio-fluorescence, gene analyses, spectrometry and telecommunication.
Lead glass is used in laser optics for printing and photocopying technologies.
References
Glass
Lead compounds