So last night I put my late sixties Dynamic under a light for about 30 seconds and to my amazement the tritium still had some life. I am going to try to capture a pic. The lume didn't glow for long (30sec?) but it was clearly visible at first. Thoughts and pictures?
I don't think the tritium is still doing anything for a watch made in the 60's. I believe the light you see is just photoluminescence, or light that is emitted when the phosphorescent pigment in the paint is energized. As long as the paint isn't damaged too much by the tritium, I think it should still give off some amount of light indefinitely. Here is my 69 speedy immediately after 30 sec of light. The faint glow doesnt last for very long though.
That is same illumination that I got. So you are saying that there are two elements at work in the lume?
Yes. Radioactive tritium was used to keep lume charged up (glowing) constantly 24/7. Most vintage tritium has died out by now, but the lume itself may still hold a brief charge (i.e.: 30 seconds). This is normal for most vintages but not all vintages.
My speedy which is 46 years old still has tritium that glows for about 20 seconds. First photo under a UV light to charge it. 2nd you can see the difference between the tritium(dial) and the superluminova(hands).
Just a correction, as omegadave mentioned above, the tritium never actually glowed. It emits beta radiation that you cannot see. It was used to excite the phosphorescent material.
I had a late 90's Speedmaster with tritium lume, and it would glow well enough all night that I could read it in the darkness once my eyes adjusted. But my 71 Speedy has no such capability. It will only glow for a few seconds if I charge it under a lamp.
The luminous paint is principally zinc sulfide doped with cupper. Also, the paint has some compound with tritium, a radiactive hydrogen isotope. The tritium emmits beta particles (basically electrons) that impact with zinc sulfide and excites them. Tritium has a semi-life of 12,6 years, so there are so few tritium in a vintage watch now. But all zinc sulfide stands there, so if it is not deteriorated for any other causes (humidity, oxidation of the resine or something similar) it would still glowing when it's exposed to light, but for short time. This is also valid for older paints with radium, but radium emissions are much more energetic that tritium ones, so it usually burn the paint and the zinc sulfide. All my watches with luminous paint still glowing a few minutes when exposed to light.
If you bought your tritium watch in 1980, there should be approx. 12.5 % of the original radioactive activity remaining If in the late sixties, about 6 % remaining
I had a Stocker and Yale military watch with the tritium tubes. Great thing for the first five years or so, and then the falloff in brightness got noticeable. It's for this reason that I loooove Super Luminova and her cousins from other suppliers and why I got my Seamaster 300 with service parts instead of an original. Tom
It's slightly different with radium lume. If the phosphor is not damaged, it would still glow strongly without being exposed to light sources.
Interestingly enough, all of my vintage Omega still glow nicely after being under direct light, yet none of Rolex glow at all and are totally dead.
Yes, I explained wrong. I was refering to zinc sulfide conservation and I forgot this big detail 226 Radium has a half-life of 1600 years, so the situation will be comparable in 16000 years I know that standard glowing paints from 1960-2000 has zinc sulfide doped with cupper for the typical green colour, and modern glowing paints has strontium aluminate doped with europium. But I don't know if older paints with radium has also zinc sulfide doped with cupper or other compounds.
so, are the completely dead ones - the ones that don't glow at all - a sign of being redone? if a dial or hands are real Tritium, should they glow faintly / briefly end of story, or can they be real and still not glow at all?
On all the watches I've tried it on, from various brands, hitting tritium lume with a camera flash in the dark, shows what lume is original and what's not. Redone lume either doesn't glow at all, or glows without a uniform consistency. I'm not saying this is absolutely the case as the sample size is only around fifteen-twenty, but it's always worked for me. Of course the question could be asked 'how do I know the lume is original', but after taking provenance into account and inspecting the dial with a loup, I've never had a dial that I was sure was original not glow. Equally, the ones where I've found issues, were either ones where I already knew or suspected a relume, or further inspection suggested all was not as it should be. It'd be interesting if others have tried this. Does the lume glow on watches you're sure are original. Is it blank on ones you always suspected were redone?
Checking the glow with a strong UV emitting flash might be a decent indicator of the presence of original lume on a tritium-dialed watch, but not necessarily so for radium-dialed watches. I say this based on my own tests, confirming Geiger counter readings on those with radium. The first time I did a UV flash test on my known radium-dialed watches, I was shocked to discover that two of them had ZERO 'glow'.... but when I went to a completely darkened room, I was able to detect extremely faint and brief (<.05 sec) glow. Most of the other radium dials (~30) had brief (albeit <0.1 sec in many cases) fairly obvious glow. The Geiger readings on the weak glowing two were strong and the watches otherwise quite original-looking, so I believe these had the original radium paint. I also noticed that on many of the other radium-dialed watches had much brighter glow in the hands, which I think indicates that the hands alone may have been re-lumed at some point. It's my understanding that a 'refreshing' with the phosphor was not uncommon with radium-dialed watches. The phosphor would degrade quite quickly from the higher energy radiation from radium. I suppose it was much easier to re-phosphor just the hands, or even just replace them. No additional radium was needed to do this! So, at least from my experience, sometimes it can be very hard to detect the glow of original phosphor on radium-dialed watches. A Geiger counter is a much more sensitive indicator for detecting if a dial has been 'cleaned' of original radium. However, no glow on a known tritium watch (because tritium doesn't degrade the phosphor like radium does) would make me quite suspicious .