Youtube Video I took of me measuring a vintage Lord Elgin watch using a Civil Defense Geiger Counter
In the old days, people did not appreciate the risks of radioactive material as we do today, as this crazy old TV commercial will clearly show you. This is not to say that all radioactive materials are imminently dangerous and that radiation is not present everywhere. Radiation comes from surprising sources: Your granite countertops, your smoke detector. Certain fruits and vegetables. Radiation is everywhere, and there are different forms of it, but radium is indubitably a risky substance that requires some caution. Whether you are a collector or a restorer of vintage watches, it’s good to have a baseline understanding of the facts and risks of dealing with vintage watches that used radium. But not panic about it either.
How Radium in Vintage Watches Came to Be:
The very first glow-in-the-dark substances really did glow. Like torches. The luminous stuff we have today in glowsticks and watch dials is fairly wimpy compared to what was. And unlike modern compounds, the old stuff did not “go out”. It continued to glow for long amounts of time. Verily, soldiers during WWII were instructed to tape over their glow-in-the-dark watches at night as not to give away their position. That’s how bright and long-lasting they were.
Why was this? Think of your old CRT television set. (Not your flat screen TV, but your clunker fishbowl TV you relocated in front of the treadmill in the basement). The inside of that TV is coated with phosphor, and phosphor glows when it is hit with electrons. That is the magic of early Television in a nutshell: An electron beam shoots out from a magnetically controlled yoke and hits the phosphor screen in the front, causing it to glow bright.
This technology was inspired in no small part by radium dial watches. The principle is identical: Phosphor is illuminated by electrons. Where do these electrons come from? Not your wall outlet as in the case of your television, but from the element Radium. The breakdown of Radioactive substances releases energetic particles into the air.
My Vintage Watch doesn’t Glow. Does this mean it’s radium free?
Absolutely not and this is the crazy part: Phosphorous burns out over the years. Manufacturers ceased using Radium in the 1960s. That was 50 years ago. The life on Phoshorous for all these watches was never intended for more than 20 years. Today all of these watches no longer glow (you can see some faint sparks under a jewelers loupe for some still). But the radium is still there. And the half-life on radium is 1600 years. The Phosphorous is disintegrated but the radium is still factory fresh!Though to look at the dial you may not even guess it ever was meant to glow.
Telltale signs of Radium
The trick is to look for blotchy marks on the dial that look like rust. Or burn marks on the plastic crystal. If you see a halo around the numbers, that means radium did its job bombarding the vicinity of the paint for decades until it left a shadow. In many cases, an old watch forgotten in a drawer will still show the hour and minute it last ran, because the hands burned marks into the plastic from being in the same position for years.
Lovely. Is my Vintage Bulova gonna kill me then?
In a word, Not likely  but there are some concerns to be aware of. [my revised opinion as of 2/12/17) The radiation from a radioactive dial is of the heavy alpha emission variety (slow moving helium atoms that are stopped by your skin) and at very low amounts. It’s not at all like gamma emissions which are the stuff of post-apocalyptic fear (and your dentist’s visit). It is only problematic if you inhale or ingest radium, which as long as its behind glass, is really hard to impossible to do.  Several readers pointed out the decomposition of radium to radon gas, which is cause for concern as it fills up the entire room regardless of being cased. Concentrations depend on a variety of factors, obviously probably best not to surround yourself with too many radium dials if this is concerning.
And even then your death from direct exposure is still not a statistical certainty. This was the tragic case of the Radium Girls. In a time with absolutely no industrial regulation 4,000 of these women were taught to sharpen their radium paint brushes by licking them (a technique known as lippointing). Essentially through repeated direct ingestation of radium over the years sickened many and some developed necrosis in the jaw, bone cancer, and death. That is the most extreme case ever. (and some good came out of this dark chapter, as workplace safety laws came into existence as a result.)
Because inhalation or ingestation is a concern, you should only worry if your watch dial is exposed from having the case broken. And the way you deal with that situation is to immediately bag it up in a ziploc bag, wipe down immediate surfaces with a wet paper towel, toss it, and wash your hands. You want to avoid touching the dial. But even if you do touch the dial, just wash it off. All you want to do is minimize the chance of radioactive dust spreading that you might inhale.
How prevalent is this problem in vintage watches?
As a restorer and collector, this is my unscientific assessment: Any watch made before 1960 has a 1 in 5 chance of having radium, with the greatest propensity being in sportier military-inspired watches (small size, round faces, wide numbers) from the late 40s to early 50s. This has been my observation measuring every project I have gotten using a geiger counter. (a Civil Defense beauty. Victoreen CDV-700 made in the 1960s. It was meant for measuring radioactivity in food storage!). As a rule, I measure every watch I work on because appearances are deceptive. Even the white faced tank watch with the gold indices might have radium dots embedded at the end of the chapter marks)
What precautions do you take as a restorer?
I often avoid radium projects as much as I can because of the extra risk they pose when the dial is uncased an exposed. In some cases, I will work on them if I think the project merits it. In this case, I use gloves (you should always use gloves anyway) and an N95 mask. Tools and surfaces are wiped down using rodico and tape, surfaces might be wiped down further with soapy water, and all of this is disposed in plastic bags which are sealed up with more tape.
Do you sell vintage watches with Radium in them?
I trend towards mid-century pieces where the problem is less prevalent…so not many, but yes. And when I do, I identify the presence of radium in the listing because it’s the right thing to do. Also because I own and enjoy such watches myself and treat them with the respect they are accorded and I encourage enthusiasts to buy them with healthy caution and just enjoy them. As I stated, the prevalence of these watches are high. Your grampies and grannies wore them for many years. Epidemiological studies would have turned up a problem if there was one, and certainly among watch repair people. In no way would I ever attempt to minimize any dangers, but just encourage a healthy understanding of them. We all varyingly risky habits, and certainly smoking will kill you faster than an old Elgin.