Lume or no lume

R

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Ridiculous

·Jul 4, 2021

I have a question that I've been wondering for a while: how much if any lume do the Tritium lumed markers/hands actually give and how quickly they lose their lume? Are for example the 60-70s watches completely lumeless or is there still something? What about the 80-90s watches?

The discolored warm tone Tritium markers sure look nice, but there is something nice also about the lume actually working: my less than a year old Speedy begins to glow even in daytime shadows and I must say, I really like this about it. Plus, I have played with the thought that which is closer to the "astronaut experience": having the "original" Tritium lume that they had, even though their experience was probably with a fresh more or less white look (not yet discolored) and actual dark time glowing...

I'm not sure there is a real point to this post 😀 Perhaps I'm just trying to work out for myself, whether I should also jump on the patina train or appreciate the non original material, but original look and functionality of the new superluminovas...

 

R

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Ridiculous

·Jul 4, 2021

And trying to explain the daylight shadow lume, I meant something like this. Just came from sunny outside into my office:

 

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SkunkPrince

·Jul 4, 2021

Tritium goes dark relatively fast. I had a Stocker and Yale military watch with the tritium tubes that lasted perhaps ten years, and after that, it was difficult to see. For many applications, Luminova really is better over the long term. You basically need to think of a tritium-tube watch as needing replacement of those tubes every other service.

 

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timecube

·Jul 4, 2021

I have a couple related questions:

* how long do radium lumes last?
Obviously, all vintage radium dials/hands are dark by now. I've understood it's because of radiation damage to the phosphor- radium retains nearly all it's radioactivity after even a few decades. (1600 year half-life)

* does tritium lume fail for the same reason? Or because the tritium itself decays?
I would naively expect after a single half-life (12 years) there would still be enough juice to make a glow. After 3 or 4 half-lives, probably not.

 

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SkunkPrince

·Jul 4, 2021

Failure of radium paint is always the deterioration of the luminous material. That said, I have Big Ben clocks from the teens where I can see the lume when dark adapted.

With tritium, it's a combination of a short half-life and also degredation of the luminous material.

The Stocker and Yale watch I reference above was insanely bright when it was new but after 15 years, it was for most practical purposes dead.

 

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timecube

·Jul 4, 2021

SkunkPrince

That said, I have Big Ben clocks from the teens where I can see the lume when dark adapted.

Interesting. I wonder if the paint is lathered on rather thick, or if there's some other reason yours survive.
You wouldn't happen to have a geiger counter?

 

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SkunkPrince

·Jul 4, 2021

timecube

Interesting. I wonder if the paint is lathered on rather thick, or if there's some other reason yours survive.
You wouldn't happen to have a geiger counter?

No, I don't. I think it's a larger amount of luminous material. A 1910s Big Ben is not a small item.

 

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timecube

·Jul 4, 2021

Vintage watches with large radium plots contain much more "luminous material" (e.g. phosphor plus radiation source) than ones with small plots, and are thereby much more radioactive, but IIRC they rarely glow any more than ones with more modest indicators.

It seems like there's some other qualitative difference with your clocks- perhaps a different phosphor mix? Perhaps if the phosphor is thicker it doesn't degrade as quickly? I am just curious how this works. Perhaps @Seaborg would know. (Perhaps not. Radiochemistry may or may not be his particular cup of tea).

 

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PandaSPUR

·Jul 5, 2021

Aside from all the technicalities on how long radium and tritium lasts, it will not produce what you called the "shadow lume" effect.
At least my tritium watch (from Ball) doesn't. Its a constant level of glow that isn't affected by anything other than the slow decay of the tritium itself. Its also not a glow that is visible in a lit room.

Makes me wonder though.. is there anyone other there that uses both types of lume?

 

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Archer

·Jul 5, 2021·Omega Qualified Watchmaker

timecube

It seems like there's some other qualitative difference with your clocks- perhaps a different phosphor mix? Perhaps if the phosphor is thicker it doesn't degrade as quickly?

Not specific to radium, but with all types of applied lume, there are factors that can influence intensity of the glow. Things like the amount (thickness) of the lume, if it is painted on a white background, and physical characteristics such as grain size of the particles can all make a difference. These things make direct comparisons sometimes difficult.

 

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gbesq

·Jul 5, 2021

Interesting discussion. I’ll add to it by asking this question. We know that, unlike radium and tritium based lume, superluminova has to be “charged” by a light source before it will glow. Do we know, though, how long superluminova will continue to glow as long as it’s charged? 10 years? 20 years? Forever? I don’t know the answer, but common sense tells me that the stuff can’t be indestructible. It has to deteriorate sometime. What I do know is that the stuff sure doesn’t patinate like tritium.

 

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Archer

·Jul 5, 2021·Omega Qualified Watchmaker

I've not seen any deterioration on Luminova really in the last 20 years or so, so apparently it will be longer than that at least.

 

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gbesq

·Jul 5, 2021

Archer

I've not seen any deterioration on Luminova really in the last 20 years or so, so apparently it will be longer than that at least.

Al, all I can say is that if you don’t know, then the rest of us are just going to have to wait. 😀

 

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SkunkPrince

·Jul 5, 2021

gbesq

Interesting discussion. I’ll add to it by asking this question. We know that, unlike radium and tritium based lume, superluminova has to be “charged” by a light source before it will glow. Do we know, though, how long superluminova will continue to glow as long as it’s charged?

That cycle is pretty short. It depends on how much of a charge... I did some research into this, looking at the spec sheets, and 20 minutes seems to be the magic number. You need 20 minutes of charge and then it will glow for at least two days, if I remember right. As Al mentioned, it doesn't seem to deteriorate long term as others have.

 

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gbesq

·Jul 5, 2021

SkunkPrince

That cycle is pretty short. It depends on how much of a charge... I did some research into this, looking at the spec sheets, and 20 minutes seems to be the magic number. You need 20 minutes of charge and then it will glow for at least two days, if I remember right. As Al mentioned, it doesn't seem to deteriorate long term as others have.

That sounds about right. I only have one superluminova watch, my 2017 SMPc, but it charges quickly in the sunlight and the lume is fantastic.

 

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timecube

·Jul 5, 2021

I can't say much about strontium aluminate (luminova/superluminova) - I have a 10 year old watch that uses it now, but it's the only one I've seen, but I AM familiar with the older zinc sulphide + copper photoluminescent paints, and can say that 40 year old samples work just as well as fresh ones for "charging" and "discharging".

If they degrade over time it would solely be due to chemical changes. Most (fortunately) seem resistant to that. It's a contrast with radioluminescent paints where the radiation causes both structural and chemical change, and the clock is always ticking on radioactive decay.