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Natural Science Forum / Earth Science / Mineralogy / August 2005portable UVA lamp
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 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.  SignatureJohn Passaneau Penn State University jxp16@psu.edu > 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 [quoted text clipped - 13 lines] > Thanks, and best regards, > Bob > 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 [quoted text clipped - 13 lines] > 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 You are aware that Raytech and several other companies offer portable units of different sizes and wavelenghts? Carl > 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 [quoted text clipped - 13 lines] > Thanks, and best regards, > Bob Signatureto reply, change ( .not) to ( .net) > 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 -- >> 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 [quoted text clipped - 12 lines] >> >> Thanks, and best regards, Bob Perhaps you could buy a filter from ratech? Or maybe Edmund Scientific or someone has a filter you could use on your home-built. sounds like fun! Carl >> You are aware that Raytech and several other companies offer portable >> units of different sizes and wavelenghts? [quoted text clipped - 27 lines] >>> >>> Thanks, and best regards, Bob Signatureto reply, change ( .not) to ( .net) > ... > > 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 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 > > You are aware that Raytech and several other companies offer portable > > units of different sizes and wavelenghts? [quoted text clipped - 29 lines] > >> > >> Thanks, and best regards, Bob 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 >> You are aware that Raytech and several other companies offer portable >> units of different sizes and wavelenghts? [quoted text clipped - 29 lines] >>> >>> Thanks, and best regards, Bob |
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