Where did all the radium watches go?

April 29, 2013 3:47 PM

Is it legal for me to purchase a used radium watch? If so, where can I find one? If I had one, how hazardous would I be to the people around me, if at all?
posted by rtimmel to Technology (13 answers total)

The National Association of Watch and Clock Collectors have a forum where they occasionally talk about issues like these. Here is one of their threads: Radium dial - danger? [upshot: bare dials can be dangerous, having one as a wristwatch, not so much]. Here's another posting on a watch forum: Radium Paint [upshot: okay if you're not opening it up, don't wear it 24/7]. The New York Times also confirms this.
posted by jessamyn at 4:02 PM on April 29, 2013

Best answer: There are lots and lots of them around. You could get one on ebay, or at any junk/antique store near you. After you've seen a few it's easy to pick them out by the "burnt" look of the hands and dial. There's not much use though - they no longer glow much or at all, because the radium has burnt out all the phosphor.
posted by fritley at 4:03 PM on April 29, 2013

Best answer: Do you mean the watches that used radium to make their dials light up? Then sure, they're legal, since the total amount of radium was miniscule --- just a tiny bit of radium paint on each number, usually.

As to where to find one: you're talking older watches, probably at least 50-60 years or more; more than likely the vast majority broke long ago; they were manually-wound watches, and it's really easy to overwind them or just have the parts wear out, at which point they'd be tossed and replaced. You're not talking about high-end expensive merchandise, you're talking about cheap everyday items.
posted by easily confused at 4:03 PM on April 29, 2013

Best answer: You'd be looking for a pre-1968 watch, and it probably won't glow that much.

Over time, the intensity of the glow from the paint will decrease because of the damage caused to the ZnS crystals by the alpha particles. Since radium-226 has a 1600 year half life, its decay is not a significant factor. Robley Evans once told me that he could estimate how old radioluminescent paint was by examining the size of the ZnS crystals under a microscope. As I understand it, the crystals actually begin to fragment because of the damage caused by the alpha particles. The damage presumably prevents electrons in the conduction band from reaching the activator sites (e.g., copper, silver) where the light would be emitted. The higher the activity of the radium-226 (and the brighter the luminescence) the faster the deterioration. One early report by Charles Viol stated that the reduction in the luminescence was due, at least in part, to a radiation-induced discoloration of the zinc sulfide crystals.

posted by zamboni at 4:07 PM on April 29, 2013 [1 favorite]

Oh, and the people most at risk from radium watches were the women (rarely men) who painted on that radium: they used to lick their paintbrushes between each dip in the paint to make the brushes form a sharp point.....
posted by easily confused at 4:08 PM on April 29, 2013

Best answer: This article on watch luminosity may also be of interest.
posted by zamboni at 4:09 PM on April 29, 2013 [1 favorite]

Response by poster: Darn. I never thought about anything other than the half-life of the radium (and the mechanicals of the watch). So tritium is the only other real option?
posted by rtimmel at 4:17 PM on April 29, 2013

If you do buy a clock with radium hands, make sure there's not an extra vial of radium paint with it. That's partly how the "radioactive boyscout" (http://harpers.org/archive/1998/11/the-radioactive-boy-scout/?single=1) got so much radium paint.

What's more common recently than radium and is still radioactive (and so doesn't need to be "charged") is tritium. I'm not aware of many new watches that use tritium paint, but if you go back 10-20 years it was common. Unfortunately given the half life of tritium that means that they've mostly lost their glow. New watches are available with tritium gas tubes, and those are extremely bright, and should last 10-20 years. Tritium is also extremely safe as long as you don't eat it since it's an alpha source, and alpha radiation is stopped by a sheet of paper (or watch crystal/gas tube, in this case).
posted by unix at 4:18 PM on April 29, 2013

You might be interested in Theo. Grey's annotated periodic table of elements, particularly the hydrogen (tritium) and radium entries.
posted by Blazecock Pileon at 5:08 PM on April 29, 2013

I've had a couple of tritium-tube luminescent watches. The glow of the hour ticks of my mbMicrotec's have just about faded out completely after 15 years, and my year-old Mondaine glows perfectly. Accepting that the watches will lose their glow after 10-20 years is ok by me. I've read several docs and the tech seems quite safe. I luv the glow of individual elements on the watch face and the convenience of having lighted hour hands, even when it's on the nightstand.
posted by artdrectr at 5:21 PM on April 29, 2013

Yup, it is a beta emitter. The much heavier He atom left behind doesn't end up going anywhere in much of a hurry.
posted by Good Brain at 10:25 PM on April 29, 2013

I have this neat tritium stick thing I keep on my keyring that makes my keys very hard to lose. Just turn off the lights and look for green."

Is this also available in iPhone case form? Yup.
posted by zamboni at 5:44 AM on April 30, 2013

FWIW I bought this tritium watch about 1.5 years ago so there are still companies out there making new ones. (Although I think that particular model is no longer made)
posted by reptile at 6:48 AM on April 30, 2013