That White Stuff In The Old BLI Glow Bottles

Topics relating to lighting control gear, including magnetic & high frequency ballast and ancilliary devices such as starters, ignitors and switchgear.
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Tom
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That White Stuff In The Old BLI Glow Bottles

Postby Tom » Wed Aug 08, 2012 11:05 pm

I know that a few of us including myself have been wondering for years just what was that white coating that Thorn/Atlas/Ekco AKA British Lighting Industries were putting in the cylindrical glow bottles in the old metal can starters...

Well after flicking through my old 1966 BLI 'Lamps And Lighting' book, it mentions that the glow bottle is 'Coated with a radioactive material to aid ionisation' Well there we have it!! :o I for one would never have imagined all those old starters are actually radioactive?? :o

Hopefully 40 plus years down the line, I guess it's pretty inactive now though?
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Re: That White Stuff In The Old BLI Glow Bottles

Postby Paul » Thu Aug 09, 2012 12:32 am

Anyone got a Geiger counter?!? LOL

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Re: That White Stuff In The Old BLI Glow Bottles

Postby FrontSideBus » Thu Aug 09, 2012 11:14 am

Sounds like radium! With a half- life of 1600 years I'd be careful with them.
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Re: That White Stuff In The Old BLI Glow Bottles

Postby SuperSix » Thu Aug 09, 2012 4:56 pm

Interesting, I know glow starters are very mildly radioactive but I didn't know that white coating was the radioactive material! It's only recently that radiation free glow starters have started appearing, that's why Philips' and a few other manufacturer's starters now have 'Radioactive-free' on the starters and boxes!

I should think those early ones are probably significantly more radioactive than modern types though!

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Re: That White Stuff In The Old BLI Glow Bottles

Postby Paul » Thu Aug 09, 2012 6:24 pm

Starters are radioactive without this white stuff!? All the time or just when striking the lamp?

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Re: That White Stuff In The Old BLI Glow Bottles

Postby Ash » Fri Aug 10, 2012 8:55 pm

Starters initially were not radioactive. And this caused ionization issues : When powering a fixture in total darkness it will just stay dead without any reaction. All components intact and no signs of life whatsever. Dark magic

The issue is to do with the photoelectric effect. To initiate a discharge (in the glow bottle), 2 things have to happen : Electrons have to be released from the metal of the electrodes into the lamp's atmosphere, and electric field have to exist to pull them strong enough to form a glowing discharge

Metals dont normally release electrons to the air or any gas atmosphere around them. There has to be some initial particle impact against the metal. to bump the electrons out (or strong enough electric field to forcefully rip them out). Ambient light - photons - are 1 particle that can do the job. But pretty much any particle will do

As such, if voltage is connected to a glow bottle in total darkness, there are metals, there is electric field, but there are no electrons in the atmosphere between them to attract. So there are no electrons to initiate the glow discharge

There are many fixtures in which the starter sticks out behind the lamp - a metal can starter with hole would be facing the lamp with the hole. I am not sure, but i think whether it is possible that a consideration might be to try to pick up the faintest phosphorescence from the lamp's phosphors, remaining since it was lit last time

In a tunnell this may actually make an awesome effect : There is no light to begin with. As soon as you light a flashlight and some photon gets into the starter and hits the metal contacts there, this starter will light up and light the lamp. The light from this lamp will start the next starters and so on - a wave of light bursting to the depths

There are some ways to overcome this - by starting at least the 1st lamp without the use of glow bottle. You can use Perfect Start or SRS fixtures, or use incandescent lamp (at least for 1 lamp to give the initial light) , and so on

Another option is to include the light source into the starter, Since any particle source will do, radioactive materials are used since all they do is "yell" particles all the time, and for many years. This radiation exists all the time in the starter so it is not dependent on external light



Radioactivity works like this : There is amount of material with X years half life. The material emits particles all the time, in quantity which is directly related to the amount of material. After X years from the start, there will be 1/2 of the original material remaining, therefore 1/2 the particle emission. After another X years there will remain 1/2 (which equals 1/4 of the initial quantity). and so on. So in short, the radioactive materials never stop "working", their "work" just cuts in 1/2 with every X years passing (this is not a sharp drop each X years, but gradual drop all the time)

What remains of it ? A radioactive material particle, as it emits its emission particle (the radiation), becomes a particle of another material. The new material may not be radioactive at all, then it stops here for this particle. The material may be radioactive as well, (but with a different 1/2 life length), in which case it will continue to decay and "move on" under the same rules

Radium is supposed to glow in the dark by itself. Perhaps only very pure radium. As the raium here is both old and might have been diluted right away (there is no need in much photons to start a glow bottle), the glow may be WAYtoo faint to be seen, even when the starter was new

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Re: That White Stuff In The Old BLI Glow Bottles

Postby James » Mon Nov 26, 2012 10:02 pm

Good description Ash!

I suspect the white coating inside the old metal can starters may be thorium oxide. That was a material once common in lamp factories, having been used as the emitter coating in mercury lamp electrodes etc (several HID lamps still today have radioactive thoria in their electrodes to assist with starting, but mainly it has been eliminated and replaced with Krypton-85 gas). It is certainly white and emits alpha particles as it decays, which would be powerful enough to penetrate the glass wall and enter the glowbottle. I think I still have a few old 50s starters with this coating and this post makes me curious now to find out what it is! If I can find one which triggers a response on the geiger counter at work I'll put it in the electron microscope and do an X-ray energy analysis to identify which elements are present in the coating.

Presumably for cost reasons (or possibly safety) this coating process was eventually eliminated in Thorn's starters, and replaced with a dose of radioactive tritium in the gas filling of the glowbottle itself. This is somewhat safer, tritium emits only beta radiation which cannot exit the glowbottle, and if it did, cannot even penetrate the skin. The only hazard would be if you inhaled the gas from a broken glowbottle, then tritium is not so pleasant once it's inside the body! While Thorn used tritium, I think some other manufacturers preferred Krypton-85 which is rather less dangerous.

Only in the past year or two has radiation in lamps become a concern, since some lawyer discovered it when Siemens decided to sell off Osram. Now everyone is faced with the hassle of trying to make all lamps completely radioactive-free.


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