In article , Michael Daly wrote:

On 28-Nov-2005, Ignoramus4324 wrote:

Glass is a UV filter, right?

Glass _can_ be a UV filter if it's coated with the appropriate material.
Some plastics are UV absorbant but even they need special treatment to
make them highly UV absorbant. Polycarbonate, for example, will block
UV, but if you want PC that is rated for eye protection against UV, you
look for UV400 polycarbonate.

Any old glass, polycarbonate and the common acrylic sheets are plenty
good for protection from shortwave UV and UVB from a broken bulb. The UVA
that gets through these materials will be less than that in a similar
quantity of daylight. Metal halide lamps designed for illumination are
actually not that efficient at producing UV - they are somewhat good at
specializing in producing visible light.

The special materials mentioned by Michael Daly are only needed when
you need a degree of UV removal much more severe than merely having a fair
amount less UV than is present in a similar quantity of sunlight that has
gone through window glass.


- Don Klipstein )