Lately, I've been investing in a bit of kit. With some thanks to input from fellow forum members, I've acquired a 9 array, 400nm LED light and a radiation detector (Geiger counter) that detects beta, gamma, and x-ray particles/wave lengths.

First, a bit on the kit. I tried a few of the jeweler's loupes with the diamond lights. These are handy, pocketable loupes with a tiny switch to turn on the 395nm (or 400nm more likely, as they're cheaper to produce) LEDs. The illumination that they provided was inadequate, in my opinion. What I required was a light source that had sufficient illumination to light up the entire face of a dial and hands, simultaneously, so that I could look for consistency between various lume plots. For the initial inspection, I don't believe that a loupe is needed at all. Far better to acquire a multi-LED light source and look with the naked eye. I found a 9 array, 400nm light, which fit the bill and is pocketable. If I need a loupe to inspect a dial or hand set, I already have a watchmaker's loupe and a foldable triplet which are of far higher quality than the cheaper diamond light loupes that are for sale from material houses and jeweler's supply shops.

I wanted a radiation detector that was pocketable, and there are no shortage of various models on the market that meets this requirement. It's not necessary to buy an old, yellow, homeland security type pancake detector with the separate probe. Though if you already have one, it will certainly get the job done. The problem with the cheaper geiger counters is that they are insensitive to alpha particles. Radium, which is what I'm after here, undergoes alpha decay, as its largest single product. Though, its subsequent decay products release alpha and beta particles, so it can still be detected with a simple geiger muller tube. I suspect that investing in a more expensive pocket size version with a pancake tube that detects alpha particles would increase the sensitivity, though I'm not sure whether this is entirely necessary for the rather simple tests that I'm using it for.

So onto the how-to...
After much trial and error, I've come up with a step wise algorithm for working up an "unknown" watch.
1. Open crystal (in well ventillated area if you suspect radium lume... radon gas has been building up under the crystal).
2. Initial test with Geiger counter. If reading is >~4x background, you likely have radium present on the hands or dial. (Note well: a Geiger counter will NOT DETECT Tritium, even though it is radioactive. The reasons are more complex and can be discussed later)
2a. If the test is negative, the watch is either Tritium or Superluminova/Phosphorescent (non-radioactive)
2b. If the test is positive, proceed to 3.
3. Remove the handset from the dial and test separately. If both hands and dial have independently similar levels of radioactivity you've established that they were likely lumed at the same time (a finding which points towards, but does not guarantee originality)
3a. If dial registers high levels of radioactivity and the hands have <~2x background, then you have established that the dial is likely older lume and the hands were later re-lumed using a non-radium luminous compound (or the hands were replaced). This would be the most likely scenario in a vintage watch where the hand lume had crumbled and the watchmaker re-lumed them using modern material to match.
3b. If dial registers <~2x background, pull out your loupe. Is this a redial?
3c. If neither dial, nor hands register >~2x background, pull out your loupe. If the watch should date to the radium era, then both the hands and dial have likely been redone.

Now, onto the 400nm light...
You can repeat the above steps to distinguish between radium and superluminova type lume, as the glow will be quite distinct. However, you will not be able to differentiate between Tritium and Radium on the basis of appearance alone. Hence the need for the geiger counter, as well.

The 400nm light is most useful for distinguishing Tritium from Super Luminova, as the two will have different glow characteristics under this wavelength.
1. Open the crystal
2. Initial visual inspection under evenly applied 400nm light source.
2a. If the hands and lume plots all appear uniform and consistent in color/glow, then you have established that the lume was contemporaneous in both. (Ie, they're either original, or were both re-done at the same time).
2b. If the lume plots from the dial and the hands don't match, one was likely to have been re-done. Until you've done this on many, many pieces, it's very difficult to distinguish with confidence, which of the two glow signatures is likely to be Tritium vs. Super Luminova, but it is possible. Time for corroborating evidence... pull out your loupe. Does the dial appear original? If so, then the dial lume is also more likely to be original and that would point towards either re-lumed or replacement hands.

In both of these tests, it's important to gain some practical experience by starting out on known examples. I've tested my various lume kits and watches that I knew to have been re-lumed to establish a baseline.

A few words of caution: Lume dust must be assumed to be extremely hazardous until proven otherwise. Take care to do this work on a work surface that can be easily decontaminated, and to be appropriately cautious. You may consider using an N95 respirator if you think you're working with particularly dusty, radioactive lume. Skin exposure is likely to be insignificant, but inhalational exposure is a real hazard.

So, what did I learn?
Well with some practice at all of this, I believe that this test will yield a rather high specificity for detecting re-lumed watches. Sensitivity values are likely to lag, as it seems quite plausible for false negative test results to exist, as would be the case in a re-lumed hand set or dial which incorporated crushed up, vintage radium material. To me this seems absolutely non-sensical; who would risk inhaling radioactive lume dust by grinding it up and re-mixing it?! But, I'm sure it has been done by fools who didn't know any better and by diligent fakers/restorers.

The results for most of my own watches were as expected: the known redials and relumes tested as such (clearly with my own interpretation bias), and I was satisfied that nearly all of the presumed-original examples, were in fact, original. However, I was interested to discover that one watch with a radium dial and beautifully color-matching handset was not original; the hands had been re-lumed and expertly color matched. Fooled me.

Is any of this relevant/practical for the average collector? I'll leave the value of "true" originality for the forums and marketplace to decide, but it's an interesting set of tools to add to the tool kit.

*Pictures would add a lot to this discussion. Unfortunately, it's very difficult to accurately photograph these things.

 

Is the radium on one vintage dial actually enough to cause radiation sickness or potentially death?

 

It depends. How much radium is on your dial? What's the method of exposure/ingestion? etc.

In short, no.

There's minimal risk to simply wearing and enjoying a vintage watch with radium lume.
See also: http://omegaforums.net/threads/radi...y-the-us-nuclear-regulatory-commission.15191/

To put it in perspective for you, based on the above report assuming that you wore the radium watch for 16 hrs/day, every day, you'd be exposed to 61 mrem/year.

You get between 2-5 mrems on a flight from NYC to LA, so wearing your watch is the equivalent of taking between 6 to 15 round trip flights per year.

It's the equivalent of getting one abdominal X-ray, or 6 chest X-rays.

Source: http://www.nrc.gov/about-nrc/radiation/around-us/doses-daily-lives.html#2

And, lest we forget, the area of your body with the most acute exposure: your wrist. Not your thyroid, not your brain, not your abdomen, not your junk. Your wrist.

 

A very interesting piece of work. It could lead to some interesting conversations at the airport if you went on an overseas buying trip.

 

"...not your junk".

tehehehe did u get that from the physicians desk reference ?


*edit You're soooooooo getting kicked out of the next watch show / auction you attend.

haha

 

I like how the Hodinkee guys take video footage of them putting on famous watches during the auction previews. I suggest they bring one of these bad boys with them next time. Adds a whole new dimension to the footage, don't it?

 

6 chest xrays a year is non trivial....

 

You can market your Dr. Oppenheimer field kit to WIS and doomsday preppers.

you'll make...billions!