Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I can shed some light on the bulb wavelength...

All regular incadescent bulbs have very little UV generating ability.
They come in coated versions where mostly deep purple (black light)
is seen. That bulb will basically generate a lot of heat (infra red)
and very little UV. You can take the regular house bulb and paint it
deep purple to give the same result. The only way to get the bulb to
give out sufficient amount of UV is to get a high power bulb (ie.
500Watts), but that also generates an enormous amount of unwanted
heat.

Incadescent, Halogen bulbs do produce a high level of UV light. The
power is dependent on the size of the fillament and voltage applied.
These bulbs generates the full spectrum of colours, but with a heavy
emphasis on the UV. That is why lights utilizing the Halogen bulb are
required (by law) to have a UV filter in front of the bulb. Regular
window glass blocks most UV, but passes visible and most IR.
Halogen lights come in all powers from 5Watts all the way up to
1000's of Watts. The material that makes up the "glass" of the bulb
is quartz, that is why they are often called "quartz hallogen".

Fuorescent bulbs. These bulbs, when totally uncoated generate only
(Mostly) UV. Extremely little visible light is generated by the
fluorescent tube (when uncoated). The visible portion of light coming
from the fluorescent tube is generated by the fluorescence of the
various powders that coat the inner surface of the tube.
The wavelength generated by the tube (other than UV) is determined by
the composition of that powder.
ALL fluorescent bulbs generate UV, but the everyday bulbs sold for
home use have a powder coating that both blocks the UV as well as
generates only visible "white" light.
The power of these tubes is determined by the length and diameter of
the tube (plasma guide). Therefore, if the tube is the same length
and diameter as a normal 40Watt tube, then it is a 40Watt tube.

In order to reduce the IR effects, or the heat from the high power
lights you can simply use a fan to dissipate the heat. You can also
be more high tech and use a IR blocking filter that passes UV only,
but that is usually cost prohibitive for most people.


John M...
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