[Rockhounds] Telling the UV from the Lamppost.

[Axel Emmermann]

> 
> All glass?

[Axel] Yes, except the kind of glass that the bulb is made of. That's
barium-silicate glass, designed to pass UV and quite expensive.

 
> I have a SW UV bulb with no markings other than "Japan" that was made in
> the 1960's. It looks to have been made of glass with two filaments
> inside. The filaments have a whitish glow next to them when 120v is put
> to them 

[Axel] If you can see the filaments when the lamp's off it's clearly a
short-wave.

> and the light is passed through a special filter, which looks to
> be made of some very dark purple crystalline material, for the SW UV.

[Axel] That would be a UV-diaphanous filter. If it's from the 60's it is
probably an old type that suffers from solarisation easily and has a limited
lifespan. Does it still perform?

> The shape of the bulb is like that of  the other in the lamp, a standard
> F4T5-BLB LW bulb.

[Axel] a 4 watt? How large is the filter?

> Your answer is good and I accept it as a general pretty good one as the
> fact that UVC does not penetrate ordinary window glass is a good
> distinguishing characteristic. And ordinary window glass can be found
> almost anywhere.
> 
> So the answer would appear to me to be:    1. find something that will
> fluoresce.  2. Put it behind some ordinary glass and see if it will
> still fluoresce with the same lamp.   3. Yes = LW; No = SW.
> 

[Axel] Yes, Houston we have lift off ;-))))

You're welcome
 
Axel!