Looking for clear (not germicidal) Fluorescent...

Zelandeth · #1 12-25-2004, 05:05 PM

...tube. Okay, so minus the phospher, it ain't fluorescent...but you get the idea. That *type* of tube.

This is entirely for curiousity's sake. I'd like to see how the discharge behaves inside the tube. There's one at college which has a partly clear tube (one end's 2400K triphosphor, one's clear), which is for that very reason (they also have an 80W "Gold" T12 (I think) fluorescent next to it...which is clearly old, and I want...). Unfortunately, we're not allowed to power that up. Same as a pile of old discharge lighting stuff I'm still working on trying to rescue. Some going back to the early 50's too.

I don't want a germicidal lamp, as that means I have to take a zillion and one precautions thanks to the UV...and I know such things do exist...but of course, I can't find one to save my life. F15T8 would be ideal as I have a fixture of that type (F15T8BLB in there just now), and can plug it straight in. Though do I have several 70W ballasts rattling around somewhere as well.

Sure someone here can make something of this, nobody else has! No one outside here has thus far done me the favour of believing me that such things exist!

Christoph · #2 12-25-2004, 05:21 PM

If the tube is clear you will get uv from it.
Chris

PhotonWrangler · #3 12-25-2004, 05:31 PM

All you have to do to block the harmful UV is to put a plastic sleeve around the lamp. You can buy a 15-25w germicidal tube and put one of those shatter-resistant protector sleeves around it. Shortwave uv will stop cold when it hits the plastic sleeve.

A small amount of longwave UV will pass through, but all fluorescent tubes emit a small amount of longwave anyway.

BTW, I have a G25T8 and it barely operates on a 15w ballast. [img]/ubbthreads/images/graemlins/icon15.gif[/img]

Lynx_Arc · #4 12-25-2004, 08:48 PM

Most likely a flourescent tube without the coating would appear similar to neon lighting.

PhotonWrangler · #5 12-25-2004, 09:05 PM

It produces a sickly greenish-blue arc. Yes, it does look very similar to neon. There are bare mercury-vapor discharge lamps that produce exactly the same color.

Which reminds me...

I have a bare mercury-vapor lamp that isn't a "germicidal" but bears the stamp "Lab Arc" on the top of the bulb. It produces that same icky greenish-blue arc.

Zelandeth · #6 12-26-2004, 03:49 PM

"If the tube is clear, you will get UV from it..." That I'd debate, as standard (soft) glass blocks shortwave UV, hence the use for quartz (or hard glass) tubes for shortwave sources.

I might just look for a G15T8 then, and find a way of stopping the dangerous part of the UV emission. As I said, this isn't for any practical use, just sheer curiousity. Having it described and seeing photos are one thing - but actually investigating it yourself is another entirely.

Anyone know of a source for this afforementioned shatter resistant protective sleeves? Never seen one of them for sale, though I do know what you're speaking of.

PhotonWrangler · #7 12-26-2004, 05:28 PM

[ QUOTE ]
Zelandeth said:
"If the tube is clear, you will get UV from it..." That I'd debate, as standard (soft) glass blocks shortwave UV, hence the use for quartz (or hard glass) tubes for shortwave sources.

I might just look for a G15T8 then, and find a way of stopping the dangerous part of the UV emission. As I said, this isn't for any practical use, just sheer curiousity. Having it described and seeing photos are one thing - but actually investigating it yourself is another entirely.

Anyone know of a source for this afforementioned shatter resistant protective sleeves? Never seen one of them for sale, though I do know what you're speaking of.

[/ QUOTE ]

I can appreciate your scientific curiosity; I'm the same way and I can remember when I wanted to see a clear fluorescent bulb also, just to see it! [img]/ubbthreads/images/graemlins/blush.gif[/img] That kind of curiosity is a good thing.

Anyway, in our part of the world we have these home improvement stores that go by the names Loews and Home Depot. I believe I've seen those shatter-shields in both stores in the fluorescent bulb section of the store. If you have any similar stores there, that's where I'd start. You might have to special-order a T8 sleeve as most of the ones I've seen in stores are for T12s, usually the 40-watt lengths. They fit around the tube perfectly.

brickbat · #8 12-26-2004, 08:25 PM

I have some germicidal lamps - the glow is a low saturation blue. Some might say bluish-white, I suppose. Your avatar is a LPS lamp, right? The discharge in a fluorescent lamp is quite similar to that - similar arc current flowing through each in about the same diameter tube - just a different color. The closest I've seen is a F15T8BL (not the BLB as you have) - It has no phosphor coating, but the ones I've seen still have an inside frost - so, sadly, you can't see the discharge.

PhotonWrangler · #9 12-27-2004, 02:53 PM

Actually the Fq15T8BL does have a phosphor coating. The mercury line is predominately a shortwave-UV wavelength; in order to make the BL-bulbs capable of putting out copious amounts of longwave UV, they use a phosphor to downconvert the shortwave to a slightly longer wavelength. Then the user can employ an optional blue filter to filter out the visible wavelengths to get black light. If you broke open a BL and a BLB lamp, you'd find that they're both coated with the same phosphor.

I have an HID lamp that has a mercury arc tube and the BLB glass, but it doesn't have the phosphor coating inside, thus you can see the arc tube through the outer envelope when it's running. Unfortunately it works rather poorly as a conventional blacklight, even though it's a 250-watt lamp, because it doesn't have the downconverting phosphor. And I paid something like 75 bucks for that lamp.
[img]/ubbthreads/images/graemlins/frown.gif[/img]

Zelandeth · #10 12-27-2004, 06:53 PM

Thanks for the replies everyone. I'm actually away from the house until the 11th jan, so I can't really look for anythign until then. Will probably jsut get hold of a germicidal lamp and figure out UV blocking then. Seems easiest.

And yes, the BL lamps do have a downconversion phosphor ~200nM - 300nM if I remember rightly. BLB is the same phosphor but with a Wood's Glass tube...oh heck.n Photonwrangler just said that didn't he...oops.

And yep, the Avatar's a mid 1980's 35W Philips SOX low pressure sodium lamp about 30 seconds after switchon. Not the normal neon fill in this one, as it is that wierd pink colour. Never did figure that one out.

And there's another reason to get one of these - it's something the collection's lacking!

PhotonWrangler · #11 12-27-2004, 07:51 PM

Ah, Wood's Glass... that's the term I was groping for when I mentioned BLB glass! Thanks for reminding me.

There's a coupla good discussions of BL vs BLB, UV wavelengths and blacklights here and here...