Comments on UVA, UVB and UVC Radiation:

Ultraviolet light, which can not be seen by the human eye, lies beyond the purple range of the visible spectrum.

As is shown, there are three different frequency ranges for the three different kinds of ultraviolet radiation.

• UVA and UVB are considered as "Sun Tanning" radiation..
• UVC is often referred to as "Germicidal" radiation

UVA and UVB Radiation:

The UVA and UVB frequencies provided by our sun reach the earth's surface, and can be considered jointly as far as their effect on glass color is concerned. UVA and UVB radiation can also be provided by special - usually quartz or flourescent - bulbs, which is convenient for testing.

There is no question but that the UVA and UVB radiation from the sun's rays can change the color of some compositions of glass, such as that used to make telephone line insulators. It has been shown that those insulators which were shaded from the sun were never colored, while some of those in direct sunlight often became colored after extensive radiation. This sun effect is chronicled in several excellent papers and articles 11, 12.

This is a telephone insulator from Dansville, New York that was originally clear, but was turned this color by exposure to ultraviolet (UVA and UVB) radiation from the sun.

This insulator also turned purple while it was in use for 30 to 40 years on an outdoor telephone line. It is owned by the telephone company engineer responsible for overseeing that line.

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