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Discussion Starter #1
I was looking at the properties of promethium 147 which Seiko used up until around 1996 when it changed over to Lumibright.
The half life of promethium 147 is 2.62 years so how do watches with original dials from the early 80s still glow? They are not photo luminescent so shining a light on them should theoretically not make them glow any brighter than the radiation that excites the pigments in the paint.
If we consider that the glow will be diminished by half every 2.62 years, then after 40 years there should be almost no discernable(less than 7%) glow left.

So why is it that some older watches with promethium 147 still glow respectably or are they simply fake dials?
 

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I don't have an answer, but the question interests me.

You got me curious. This is what I got from Wikipedia:
Some signal lights use a luminous paint, containing a phosphor that absorbs the beta radiation emitted by promethium-147 and emits light.[17][41] This isotope does not cause aging of the phosphor, as alpha emitters do,[55] and therefore the light emission is stable for a few years.[55] Originally, radium-226 was used for the purpose, but it was later replaced by promethium-147 and tritium (hydrogen-3).[56] Promethium may be favored over tritium for nuclear safety reasons.[57]

What is Lumibright made of?

Is there a generic form of Lumibright?
 

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Discussion Starter #3
I don't have an answer, but the question interests me.

You got me curious. This is what I got from Wikipedia:
Some signal lights use a luminous paint, containing a phosphor that absorbs the beta radiation emitted by promethium-147 and emits light.[17][41] This isotope does not cause aging of the phosphor, as alpha emitters do,[55] and therefore the light emission is stable for a few years.[55] Originally, radium-226 was used for the purpose, but it was later replaced by promethium-147 and tritium (hydrogen-3).[56] Promethium may be favored over tritium for nuclear safety reasons.[57]

What is Lumibright made of?

Is there a generic form of Lumibright?
Lumibright is made of Europium doped strontium silicate-aluminate oxide. It is non nuclear and reacts to light. It stores the light that falls on it then lets it radiate as visible light in the colour of the pigments in the lume paint.

The original product, called Luminova, was developed by the Nemoto Co. in Japan in the early 90s. Seiko makes it's own Lumibright under license to Nemoto.
Tritum has a half life of 12 years so it lasts longer but it does give off beta radiation in small amounts. Typically, the radiation cannot even penetrate a crystal on a watch so it is pretty safe to use.

All the materials use to make paint glow in the dark are susceptible to moisture so even if promethium or tritium doesn't glow, it will still be active.
 

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Lume was sold, and still is sold in a powder form,(as well as a premix) some I guess could mix to different strengths ?? - just a thought.

I have a few vintage citizen divers that I have been considering having relumed but I've seen some bad relume jobs.I haven't yet broached the subject with my watchmaker
as I think he can be temperamental if question him about his skills with a lume needle - I think it can make or break a watches appearance
 

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Discussion Starter #5
Lume was sold, and still is sold in a powder form,(as well as a premix) some I guess could mix to different strengths ?? - just a thought.

I have a few vintage citizen divers that I have been considering having relumed but I've seen some bad relume jobs.I haven't yet broached the subject with my watchmaker
as I think he can be temperamental if question him about his skills with a lume needle - I think it can make or break a watches appearance
I'm not looking for product as I already have a NoctLumina Kit.
Two things are important; the background that the lume is painted onto and the thickness of the lume.

I probably already answered my own question with my description of half life and moisture or lack thereof.
 

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The tritium era watches look nothing at all like they did when new. Let’s say your have a 6105 from 1975. And it’s at 100% brand new capacity to emit. Around 1987 between beta decay of the tritium into helium-3, and degradation of the phosphor, it is at best 50% as glowy as when it was new. (I’m roughly rounding to 12 yr half life in my head, it’s actually about 12.3 ish.) I have been told the 6105 manuals said tritium. I recall my 6309 manual saying tritium. I recall my 7002 manual saying promethium.

You see some guys with new 6309s and decide to get one. It looks like your 6105 did new.
About six years later it still looks pretty good, about 70% as glowy as new. But you can’t find it anywhere. You dig your 6105 out of a drawer. It still works and runs. But is maybe about 1/3 as glowy as new.

You decide to go buy another 6309, but it’s 1993 and they don’t have them any more. You grab a 7002. The tritium paint era has ended. This has promethium. I don’t think or recall they brand new Lume of a 7002 was as good as a brand new 6309, buts let’s say it was. Promethium-147 will also decay into another isotope. But only has a half life of a little over 2.5 years. I also think Seiko was switching from radioactive to

Only three years later it’s 1996 and you are sick of how crappy the Lume is on your 7002. You dig out your old 6105, it is still about a quarter of the glow it had when new. Your 7002 is bright than that. It’s about 40 plus % what it was when new. But it is nowhere near as a old. You keep wearing the 7002.

It‘s 1999 and you are getting ready for the Y2K TEOTWAWKI. Your 7002 is not even 20% as bright as when you bought it. You dig the 6105 out of a drawer again. It still works, and is actually a touch brighter than 7002 with over 20% of its original glow.

You are moving to your remote, rural compound to survivalist out the coming apocalypse and while moving furniture find your old 6309. Holy crap. It still has about half the glow it did new. Over Twice as bright as either the 1975 tritium 6105 or 1993 7002.

Around 1993 non radioactive photoexcited photoluminescents for quality products were getting into strontium aluminate. This was better than previous or cheap product zinc type phosphorescents. Theoretically these won’t age, degrade, get weaker, etc. But they must be charged with light.
put it in a drawer and it will have no flow when taken out the next night until charged with light.

Basically, in theory,
and have just grabbed the HP15C to be a little more accurate than off my head above.
the 6105 you bout in 1975 might have about 8% of the Lume potential now in 2020 as it did when new.
the 6309 you bought in 1987 about 15%.
the 7092 you bought in 1992 about 0.08%.
the SKX007 you bought in 2000 perform exactly as it did when new.

And this is just based on remaining tritium or promethium, not other material degradation, mold, etc.

There has been some information out there that Seiko never used tritium, only promethium.
But that does not match other information, and brand new 80s divers looked just like tritium compared other military items with tritium Paint markers. The 7002 had a much different distinctive appearance And was not on par with a tritium look.
 

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Discussion Starter #7
The tritium era watches look nothing at all like they did when new. Let’s say your have a 6105 from 1975. And it’s at 100% brand new capacity to emit. Around 1987 between beta decay of the tritium into helium-3, and degradation of the phosphor, it is at best 50% as glowy as when it was new. (I’m roughly rounding to 12 yr half life in my head, it’s actually about 12.3 ish.) I have been told the 6105 manuals said tritium. I recall my 6309 manual saying tritium. I recall my 7002 manual saying promethium.

You see some guys with new 6309s and decide to get one. It looks like your 6105 did new.
About six years later it still looks pretty good, about 70% as glowy as new. But you can’t find it anywhere. You dig your 6105 out of a drawer. It still works and runs. But is maybe about 1/3 as glowy as new.

You decide to go buy another 6309, but it’s 1993 and they don’t have them any more. You grab a 7002. The tritium paint era has ended. This has promethium. I don’t think or recall they brand new Lume of a 7002 was as good as a brand new 6309, buts let’s say it was. Promethium-147 will also decay into another isotope. But only has a half life of a little over 2.5 years. I also think Seiko was switching from radioactive to

Only three years later it’s 1996 and you are sick of how crappy the Lume is on your 7002. You dig out your old 6105, it is still about a quarter of the glow it had when new. Your 7002 is bright than that. It’s about 40 plus % what it was when new. But it is nowhere near as a old. You keep wearing the 7002.

It‘s 1999 and you are getting ready for the Y2K TEOTWAWKI. Your 7002 is not even 20% as bright as when you bought it. You dig the 6105 out of a drawer again. It still works, and is actually a touch brighter than 7002 with over 20% of its original glow.

You are moving to your remote, rural compound to survivalist out the coming apocalypse and while moving furniture find your old 6309. Holy crap. It still has about half the glow it did new. Over Twice as bright as either the 1975 tritium 6105 or 1993 7002.

Around 1993 non radioactive photoexcited photoluminescents for quality products were getting into strontium aluminate. This was better than previous or cheap product zinc type phosphorescents. Theoretically these won’t age, degrade, get weaker, etc. But they must be charged with light.
put it in a drawer and it will have no flow when taken out the next night until charged with light.

Basically, in theory,
and have just grabbed the HP15C to be a little more accurate than off my head above.
the 6105 you bout in 1975 might have about 8% of the Lume potential now in 2020 as it did when new.
the 6309 you bought in 1987 about 15%.
the 7092 you bought in 1992 about 0.08%.
the SKX007 you bought in 2000 perform exactly as it did when new.

And this is just based on remaining tritium or promethium, not other material degradation, mold, etc.

There has been some information out there that Seiko never used tritium, only promethium.
But that does not match other information, and brand new 80s divers looked just like tritium compared other military items with tritium Paint markers. The 7002 had a much different distinctive appearance And was not on par with a tritium look.
Thank you for this info. I often wondered why the 7002 lume(if it was still promethium) did not hold up like what was on the 6309. I suspect that you may be right about it being tritium.
Seiko would obviously not want to make any noise about it since both tritium and promethium are radio active. Neither one is hazardous to humans if handled intelligently.
 

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In that era tritium or promethium in a paint added to a dial was no big deal.
It was not a factor that scared anyone away from a watch.
It’s simply to minor to be of a concern unless you went around scraping the Lume out of hand sets and off dial indices of a bunch of watches and snorted lines of it.

Radium was another story. It has a half life of about 1600 years.
The only reason old radium dials and gauges don’t have readable Lume anymore is because the zinc sulfide phosphorescent is degraded and shot. The alpha decay that excites the phosphor, like beta decay, is harmless in a watch. Tritium is still readily available for Lume, now just sealed in little tubes instead of directly applied in a paint.
But, a small percent end of the time radium will gamma emit.
 
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