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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