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Does anybody know why black light make the lume material glow? The reason I ask is because last night I was at a club and my watch was glowing really bright.

Thanks,

Yogev
 

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The glow material is sensitive to visible light and also is charged by the ultra-violet range light that you cannot see as it is higher in frequency and energy.

Now in normal lighting, the lume is glowing away, but you don't see it well because your eyes have to adjust to the brightness. At the nightclub, the visible light is dim, and the ultraviolet light (really it's near-ultraviolet) of the blacklight is fairly bright. Since your eye is not as sensitive to the UV, but the lume on your watch is sensitive, you see the glow of the watch at full strength since it is being charged up like in a bright normal lighting situation.
 

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Interesting. Thanks for your replies. One question maybe dumb or not but would like to know. If the lume is charged so strongly, does it take from the life expectancy of the lume material?

Yogev
 

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Interesting. Thanks for your replies. One question maybe dumb or not but would like to know. If the lume is charged so strongly, does it take from the life expectancy of the lume material?
No. modern, Luminova/lumbibrite kind of lume compounds have no theoretical expiration. exposure to UV light does not damage them. exposure to the environment (humidity and the like) will damage the physical state of the compound)
 

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No. modern, Luminova/lumbibrite kind of lume compounds have no theoretical expiration. exposure to UV light does not damage them. exposure to the environment (humidity and the like) will damage the physical state of the compound)
Thats cool, I would have figured since it is a radioactive material, it would have had some sort of half life. |>
 

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I don't think there is any radioative stuff in it. At least not anymore.
 

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Thats cool, I would have figured since it is a radioactive material, it would have had some sort of half life. |>
The only radioactive material used in the lume of modern watches is Tritium, and that is not that widely used either. When Tritium is used in a watch, the dial is normally marked with "H3" or "T-25" somewhere to indicate that a radioactive isotope is used, even though it is a very, very weak radioactive isotope. It has a half-life of 12.5 years and a useful life of 25 years (thus a "T-25" marking).

Going back several decades in time, highly radioactive Radium was used for lume. It would burn-out the luminous material too and still be highly radioactive (in relation to the amount used) even after it stopped glowing in the dark.

The regular lume that you have to charge up with a light first should not have any radioactivity to it.
 

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That's odd, a Seiko book I have has some sort of warning relating to that. I'll have to look back and see if I read it wrong... it's happened before!
 
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That's odd, a Seiko book I have has some sort of warning relating to that. I'll have to look back and see if I read it wrong... it's happened before!
That could be old radium based lumes which were very popular some decades back. They usually cause telltale crystal burns if left stopped for some time.
 

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That's odd, a Seiko book I have has some sort of warning relating to that. I'll have to look back and see if I read it wrong... it's happened before!
The lume you are referring to is called Promethium. It is the in-house compound Seiko used to use in their watches before seiko developed Lumibrite and superluminova. You'll notice that a lot of older seiko's will have a P in their dial code (instead of the T often favored by other brands which used Tritium). This denotes the use of promethium.
 
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