Hey guys, I just watched a YouTube video of a 4 foot long T12 that never had phosphors applied to the inner walls and was supposedly used for educational purposes. I have always kind of wanted something of the sort, are there any chances of getting a 24", 36",or 48" T12 like this? Basically I know I could get a germicidal bulb maybe put i'm afraid of that unless there was someway to make it safe to view the low pressure mercury vapor glow as much as I wanted.  I think it would be so neat to have one just actually see the glow and educate people...such as the kid who thinks fluorescents don't need mercury lol...and to just enjoy the soothing glow :-) … I am similarly fascinated by the plasma inside a true red/orange clear neon tube, I love to watch upclose! I'm sure many of you can relate! :-) As long as it were a standard glass tube missing phosphors would it still be safe or do the phosphors block uv also, and where in the world would we find them? I'm gonna guess this will be very tough...

I'm sure someone will correct me if I'm wrong but don't all florescent lamps generate a UV discharge, and it's the phosphor coating that turns this discharge into visible light? I always thought germicidal lamps were basically just florescent lamps without any phosphor coating, or is there something special about the glass/fill gas?

The phosphor cant catch it all due to its nature being porous and thin, also there might be jut wavelengths that it does not convert at all. It is the glass that blocks the UV that remains after the phosphor in normal tube. Germ tube is masde of different glass to let the UV out

The glass in those clear Germicidal lamps is engineered to allow UVC to pass, so yes, you can see a faint purple arc. But, WARNING...UVC light, even looking at it for a few moments can cause severe UV burns inside your eyes and on the skin. (20 seconds of looking at a G-30T8 is enough where you'll wake up in the middle of the night with burning "sandpaper" in your eyes.

In a standard tube, the phosphors ABSORBS most of the UV energy and converts it to visible light, the glass blocks the remaining... a small amount of near-UV may carry a few inches from the tube...

Just be really careful with clear germicidal tubes :-)

atleast there some half coated tubes in existance. such as my Magno-Tronic tubes that strip like a zebra
and show the inside low pressure mercury glow as well the Phosphor.
http://www.lighting-gallery.net/gallery/displayimage.php?album=2193&pos=23&pid=70427

 How ever if you can find some Philip F17T8 or F18T8 from holland, they have a large glass pill inside
that very easly come lose from the cathode gaurds, wich will scratch the phosphore up, if you can get that
glass pill to come lose by taping it on the ends a few times. and once that free slowly move the tube
back and forth it stratch the phosphor on the glass, resulting a clear portion of the tube. this have be
done with out hitting the cathod as you dont want to scrape the emitter off from it.

 third option is contacting the lamp manufactor see if they can make you a phosphorleas tube.

The phosphor by far does not absorb all the UV. It's thickness is a compromise: Thicker layer utilize more UV, but block the visible light as well. So the thickness have to be exact on the optimum. But that mean not all the UV being captured by the phosphor, few 10's of % pass through.
The task to really block the dangerous UV (so reduce it to 1/1000 or less) to reach out lies on the glass.
Here the property of the regular soft glass help a lot: It is by itself highly opaque to the UV, so if it is used, the tube is not dangerous, even when thereis nophosphor at all (in demo tubes, engineering lamp versions for ballast designing,...)

But when the UV is adesired output, a special glass is used and then such tube become an UV hazard

Germicidal tubes are made from quartz or fused silica. This is the reason why these lamps produces dangerous short wave UV radiation.

Hey guys, I just watched a YouTube video of a 4 foot long T12 that never had phosphors applied to the inner walls and was supposedly used for educational purposes. I have always kind of wanted something of the sort, are there any chances of getting a 24", 36",or 48" T12 like this? Basically I know I could get a germicidal bulb maybe put i'm afraid of that unless there was someway to make it safe to view the low pressure mercury vapor glow as much as I wanted.  I think it would be so neat to have one just actually see the glow and educate people...such as the kid who thinks fluorescents don't need mercury lol...and to just enjoy the soothing glow :-) … I am similarly fascinated by the plasma inside a true red/orange clear neon tube, I love to watch up close! I'm sure many of you can relate! :-) As long as it were a standard glass tube missing phosphors would it still be safe or do the phosphors block uv also, and where in the world would we find them? I'm gonna guess this will be very tough...

One option is to use a "germicidal" lamp with a filter and shielding to prevent exposure to direct or reflected UV.
If you choose to work with UV at all, you'd be well-advised to have glasses which are expressly intended for UV BLOCKING, these often have yellow lenses and are not just "sunglasses." AND DON'T watch up close!
A germicidal lamp could be placed inside a larger glass tube for shielding.
One can acquire a glass 'shielding tube' by removing the end from an ordinary fluorescent tube and cleaning out the phosphors.  A gas torch, or burner, can "flame polish" sharp edges of broken glass.
Online, find information on 'neon' or "cold cathode" lamp fabrication.

p.s. A "Germicidal" tube is NOT the same as an "Ozone Producing" tube.

Disclaimer: Don't do things which you or others may live to regret... or not.

Funkybulb : In Philips European lamps i seen the capsule have a metal wire from the cathode melted into it, making that one fall out of its mounting looks like impossible. How you managed to do that ?

Germicidal tubes are made from quartz or fused silica. This is the reason why these lamps produces dangerous short wave UV radiation.

All the tubes I have seen did not used quartz (too expensive, fluorescent machinery can not handle it due to too high temperatures required for processing, would require different seals technology, so again not possible to make on regular machinery,...), but quite regular glass, only purified to not contain any traces of some elements normally responsible for the UV absorbtion in the standard glass (for sure FE, but may be some other elements have to be avoided too, if the glass have to be UV transparent).

@ Mike

We had 4 foot educational lamps in our high school science labs - the phosphor was only up to the middle, the rest clear. It was made to show students how the fluorescent lamp works. It was all set up on a board and could be brought out to the class and used at short notice. Rather collectible now I would think.