Do you know someone who is reluming dial with Tritium ?

[tode1640]

I'm not looking for a "torch glowing", but just natural glowing when you are "activating" the Tritium with a powerful source of luminosity.

There is no need to "activate" tritium. The radioactive tritium in the paint causes the luminous dye to glow in the complete absence of light. You can leave the watch in a drawer for a year, and it will still be glowing when you take it out. The snag is that the half-life of tritium causes it to decay. After 12 years, there will only be half the radioactivity at the start - and that means the glow will be pretty faint. By 20+ years it is barely noticeable. That is why vintage tritium watches rarely glow. I presume that the tritium relume that some modders do replicates the appearance of an old tritium dial rather than a brand new tritium dial (i.e. it will have a yellowed aged look, and won't glow).

old exit signs used tritium

Modern ones still do. They use beta lights, which contain tritium in completely sealed tubes. They will always glow without using any power, and so are useful safety devices. They do need to be replaced every few years, though, because they get fainter as the tritium decays.

Couldn't we commission some mercenaries to hijack a shipment of Russian nuclear warheads, just so we could scrape out the sweet, sweet tritium inside?

Ah, if you are going to do that, what you want is radium! That has a half-life of thousands of years, and was used in watches up until the 1930s. Sadly, the stuff is seriously dangerous to factory workers (many of them died a horrible death, in the days when it was being used). However, the decay is so slow that effectively the watch will permanently glow in the complete absence of light. I have seen a vintage 1920s watch with a radium dial - still glowing as brightly as the day it was made.

[Jkay]

It sounds like some people in this thread think the luminous paint on the hour markers and hands are tritium. That is not the case.

Tritium is a gas. Tritium is mixed with a luminous paste to make the paint for the dial and hands.

The incredibly small radioactivity of the tritium (it can not penetrate the watch crystal or your skin) activates the luminous material of the paste and makes it glow, in the same way that light makes luminova lume glow.

That is why you can still "charge" the lume of a dead old tritium watch. It is the luminous paint that glows, not the dead tritium.

So you are asking why "tritium" ages so differently but that is the wrong question. It is the binder of the paint that yellows. Tritium is a gas and it certainly does not "discolor". Why does any paint binder discolor .. It depends on what it's made from and what it is exposed to over time.

[tode1640]

Tritium is a gas. Tritium is mixed with a luminous paste to make the paint for the dial and hands.

Tritium is indeed a gas - it is, in fact, hydrogen. It is a radioactive isotope of hydrogen, but chemically it is identical to non-radioactive hydrogen. That means it can be incorporated into any compound that contains hydrogen. For example, water is composed of hydrogen and oxygen - so tritiated water is composed of tritium and oxygen. It is identical to ordinary water in every respect, other than the fact that it is radioactive (don't try drinking it!). The mixture that was used to paint watch dials consisted of Zinc Sulphide, a tritiated polymer and various dyes and binding agents. Zink Sulphide is luminous, but on its own it doesn't last long without being continually excited. Tritium would indeed continually excite it. However, when the tritium decays what you would be left with would be something that could indeed by charged by light - but would then only glow very briefly. We are certainly not talking superlume here. This is why 30 year old tritium watches tend to glow slightly at best.

I have no idea what is in the mix that vintage relumers use. I suppose it would be possible to create a superlume that in daylight looked like aged tritium lume. Alternatively it would be possible, and probably more authentic, to create a non-glowing "lume" that looked like elderly trotted lume. If the person making the mix had access to tritiated compounds (which are used for various applications) it would even be possible to mix up a genuine tritium lume. However, tritiated material is not available to the general public - one would need contacts in specialist industries to get hold of it.

Incidentally, I used to work in a lab where we routinely used tritiated amino acids for experiments. This stuff came as a liquid and the bottles were kept in locked cabinets along with a lot of legally required paperwork too keep track of every drop.

[Jkay]

Our modders here can and have created custom modern luminova mixes which are colored to appear as any "flavor" of aged tritium as the owner desires from burned yellow to creamy tan and brown.

They will also at your request dim down the modern luminova to recreate the faint glow of a 50 year old tritium dial.

Oh and thank you for the interesting chemistry knowledge.

[Jkay]

Oh! And yes; if tritium escapes into the atmosphere, it does readily combine with the air to form molecules of radioactive water.

The only way I know of to aquire tritium is to purchase commercial EXIT signs, which contain quite a bit of the stuff, so that they may glow in the event of a power outage inside your building.

[mastersdom]

I re-lume but wouldn't touch Tritium paste. Not worth the risk, even for danger money. Tubes are different of course.

[tode1640]

I re-lume but wouldn't touch Tritium paste. Not worth the risk, even for danger money.

Very wise. It is nasty stuff - that is why the watch manufacturers all stopped using it. It is safe enough once in the watch, but there were significant dangers to factory workers. It isn't as dangerous as radium (quite a lot of watch factory workers died from radium poisoning in the early 20th century) - but it is still unpleasant. I handled various tritium compounds when I used to work in a lab, and you need to be quite careful. The gloves that we wore, and the pipettes that sucked the stuff up would all be sealed into drums and treated as low grade nuclear waste. We only handled it inside sealed cabinets, so there was no possibility of it vaporising and getting into the room, and every microlitre had to be accounted for. It would be far too dangerous to touch at home - even if you could get hold of it.

[Watchmeister]

Great thread. And of course all the scientists have it right, Tritium is a gas and it all about the substrate or bonding agent used. I do think there were wide differences. My '66 5512 glows much better than my PAM 170 which is less than 10 years old and my 23 and 28 glow even less. And I know all the arguments about exposure to air, etc. But I concluded that the bonding agent makes a huge difference. I know a number of folks have suggested that the move from tritium to luminova was safety related but I believe folks moved onto Lume because it's critical properties (brightness, longevity and period of time to degradation) are so much better. Until recently PAM still made dials with tritium markers (and not in tubes) - submersibles, etc. I know radium is a whole other story but I don't think the levels of radioactivity in tritium on a dial are nearly that bad. I do still use tritium (albeit older samples) and find that tritium combined with very low quality lume as bonding agent and a touch of tint or paint to color appropriately and further reduce the glow matches up very nicely with vintage tritium and de facto is tritium. So I go with that. It is funny that even this morning I woke up in the dark and there was the remote to an ancient tube TV in the room with the principle buttons still glowing vaguely. Tritium of course.

[mastersdom]

While I wouldn't work with it myself, I would LOVE to have new tritim lume! Not keen on the tubes unless you can bury them under some paste somehow

[tode1640]

While I wouldn't work with it myself, I would LOVE to have new tritim lume!

Why stop at tritium - radium is vastly superior! You will get a really bright glow that will last the lifetime of the watch (radium has a half life of thousands of years). The snag is that you quite rightly say that you wouldn't work with it yourself. It is possible to work with radioactive materials safely - I have done so. But the precautions would get prohibitively expensive for most commercial manufacturing processes, and the disposal of waste (especially radium) becomes a big issue.

[Watchmeister]

Did one in radium years ago - 3646. I posted it here years ago I think. Only ever found one guy willing to do it and with access to the radium. At the time I had the guy run a Geiger counter or whatever you call it over it before sending it. That stuff does glow forever.

[Jkay]

The women in the watch factories applied the radium lume with paint brushes. To make a super fine point on the brush they would lick it with their tongue over and over throughout the work day, eating huge quantities of radium.

They didn't become deathly ill by simply working with it; they ate it daily.

[Jkay]

Looking into this, it seems that once the dial painters were instructed to not eat the radium and were given rudimentary protective clothing there was not another case of radium caused illness from 1920 until production ceased in 1968.

So it seems pretty darn safe to use, even with 1920s era gloves and handling it directly for decades as a profession.

Research on the "radium girls" at argonne national labs determined that lifetime exposures of 1000x natural levels produced no ill effects in those women.

[tode1640]

So it seems pretty darn safe to use, even with 1920s era gloves and handling it directly for decades as a profession.

The point is, though, that accidents - spills, and the like - can easily happen. Sure, once people stopped eating radium there were no more obvious cases of radiation sickness. Incidentally, the worst problems were not with the brush lickers, but with their supervisors who used to drink the glowing green paint just to demonstrate quite how "non-toxic" it was! However, even after even after the dangers were realised occasional exposure would still have occurred. This won't cause any short term problems - but it is extremely carcinogenic. How many factory workers in the post 1920s period died of cancer? They might, of course, have died of cancer anyway - but some were, no doubt, due to accidental exposures in the factories.

It is quite possible to handle radiochemicals safely. This is often done in research labs, and in some specialised industry. The problem is that in order to do it safely you do need to take fairly extreme (and therefore expensive) precautions. All workers need to have regular medicals, and wear exposure meters. The material itself needs to be handled in sealed cabinets that will contain any vapours and spillage. The workers need to wear protective clothes. The gloves and any equipment that touches the stuff needs to be disposed of carefully (usually by sealing it up and dumping it into a disused coal mine!). There needs to be a lot of paperwork done to track the usage of radioactive material. The work environment needs to be continually monitored, and regularly decontaminated. There need to be emergency procedures in place, in case of any spillage or leak that breaches the normal safeguards. All of this is now a legal requirement for any industry that wishes to use radioactive material. This makes it prohibitively expensive, for many purposes. I am pretty certain that the reason that radium and tritium are no longer used in watches is simply because of the expense of handling it safely in factories.

Research on the "radium girls" at argonne national labs determined that lifetime exposures of 1000x natural levels produced no ill effects in those women.

These sort of studies are notoriously difficult to interpret. So called "safe" levels of radiation exposure are often educated guesses. The problem is that cancer is triggered by errors in cell division - one cause of which is radiation. Everyone is continually bombarded with natural radiation, and everyone is at risk of cancer. Exposure to additional radiation does increase the risk of cancer, but it isn't a linear relationship (a thousand times the natural level of radiation doesn't translate into a thousand-fold increase risk of cancer). However, there is a relationship, but it can take decades before this becomes apparent. Therefore, it is extremely difficult to do these sorts of studies and even more difficult to interpret the results. Hence the view of most Health and Safety regulations, that exposure to radiation should be minimised.

Radium and tritium (particularly tritium) are also particularly insidious - because they are easily absorbed into the body, which would mean that the exposure to radiation becomes internal - which is harder to spot and far more dangerous than exposure to an external source.

Edited June 25, 2012 by tode1640