[zxcvbob]

I'm toying with the idea of getting a battery-powered fluorescent lamp
(sold for use in a closet, etc) and replacing the lamp with an
appropriately sized germicidal lamp (G4T5 or G8T5) to use as field lamp
for looking for fluorescent minerals. I don't think a BLB lamp provides
short enough wavelength for most purposes, although they are cheap and
intend to try that too.

I am aware of the radiation burn danger from G lamps. Could something
like this be used safely without a filter? What kind of filtering is
the cheap plastic diffuser that comes with the lamp likely to provide
(until it becomes solarized)

Will polycarbonate eyeglasses provide adequate UV eye protection as long
as nobody stares at the lamp?

Thanks, and best regards,
Bob

 

[John Passaneau]

The problem is the germicidal lamp will produce a large amount of visible
light along with the short wave UV. This will wash out all but the strongest
fluorescent responses. So the filter is to block the visible light and pass
the shortwave UV. BLB lamps produce what is called "long wave UV". The BLB
means that it has a built in long wave UV filter that blocks most of the
visible light and passes the long wave UV. Some minerals responded to long
wave UV, but more respond to "short wave UV" produced by germicidal lamps.
The filters used with long wave lamps absorbs shortwave UV. Most plastics
and normal glass absorbs shortwave UV. Filters for shortwave UV are
expensive and they don't stop danger from burns from the UV light. A strong
shortwave UV lamp is must be used with care whether it has a filter or not.

 

[JohnR66]

I'm toying with the idea of getting a battery-powered fluorescent lamp
(sold for use in a closet, etc) and replacing the lamp with an
appropriately sized germicidal lamp (G4T5 or G8T5) to use as field lamp
for looking for fluorescent minerals. I don't think a BLB lamp provides
short enough wavelength for most purposes, although they are cheap and
intend to try that too.

I am aware of the radiation burn danger from G lamps. Could something
like this be used safely without a filter? What kind of filtering is the
cheap plastic diffuser that comes with the lamp likely to provide (until
it becomes solarized)

Will polycarbonate eyeglasses provide adequate UV eye protection as long
as nobody stares at the lamp?

Thanks, and best regards,
Bob

The little 4" lamp should be plenty. The T8 (or G8 in this case) takes the
longer lamp that needs to be fed 8 AA (usually). This gets expensive and
rechargeable batteries tend to die in the middle of using the thing.
You have to use it with the plastic dome off as it blocks much of the UV
spectrum. I made a reflector to aim and control the light drom aluminum
foil. These battery operated units under drive the lamp. The 4 watt tube
will get about 2 watts. The radiation risk should be limited, but I'd keep
my eyes a good distance away from it. Putting the light near a plastic bag,
I can smell the UV starting to break it down!.

I got my G4T5 bulb at www.bulbdirect.com for $11 shipped (2002 prices), so
for about $20 you can make a rig. I don't have a visible light filter on
mine. It may cost more than the whole rig.

John

 

[zxcvbob]

You are aware that Raytech and several other companies offer portable
units of different sizes and wavelenghts?

Carl

I assumed that someone made them, but I thought it would be more fun to
make one for about $20.

But I also didn't know the germicidal lamps enough visible light to
cause a problem. (I haven't looked up the electromagnetic spectrum for
mercury lately, but I thought most of the energy was at 2537 Angstrom).

Best regards,
Bob

--

 

[George Pontis]

...

But I also didn't know the germicidal lamps enough visible light to
cause a problem. (I haven't looked up the electromagnetic spectrum for
mercury lately, but I thought most of the energy was at 2537 Angstrom).

Yes, the germicidal lamps put out most if their energy at that wavelength. That is
UVC and not the UVA that you seek. It will make things fluoresce like crazy but
there is much more of a safety problem.

Have you considered one of the little keychain UV LEDs ? Photonlight sells them at
370nm and 405nm. Less than $20 and very handy.

FYI: http://www.photonlight.com/products/ultraviolet_photon.html

 

[Joe]

In these sort of lights, the filter is by far the most expensive part. At
one time, I had considered building my own, but it won't save any money. I
also suspect that the output of the germicidal lamp would destroy the
plastic fixture in short order.

Now there are collectors who have added Medium-Wave fixtures to their
display; even more expensive than SW.

Joe

 

[JohnR66]

Here mine "cooking the books" so to speak. (refector removed)
http://home.att.net/~jriegle/uv.jpg
It gives of a weak bluish light and generates a bit of ozone. The white
plastic reflector turned yellow in minutes, but the black plastic should not
be harmed. The main discharge column looks white due to overdriving the
camera sensor. It is really a violet blue color.
John