Submitted by Reverend Rob on December 25, 2014 - 1:19pm

A lot has been said over the years about Radium and its ill effects, and how it relates to horology. Watchmakers typically have had to contend with a vast array of toxic materials, Cyanide, Trichlorethylene, Carbon Tetrachloride, Ammoniated cleaning solutions, both water and hydrocarbon based, Rouges and polishing mediums, and of course, Radium.

I recently had the opportunity to use a Geiger counter on a variety of test subjects, and the results have surprised me. 

First I tested a tiny ladies watch, no bigger than a dime, and it topped out at 12.2 microsieverts per hour. This seems to be a kind of average for a lot of non-military watches, and depends, of course, on the amount of Radium appluied to the dial. After being stripped of Radium, the dial still remains hot, as does the movt.

I tested my 1952 Rolex and it kicked out 21.3 microsieverts per hour, which was very high, considering it had been stripped and re-lumed. 

I tested a car clock I had stripped in school, and it still kicked out 18.5 ms/hr. 

An RAF pocket watch bomb timer  put out over 30 ms/hr. and that was just from one hand. 

I recently checked a very thin hand from a Universal handwind from the early 60's and it put out a whopping 52 ms/h. 

For comparison, where I live, background radiation is .1 to .2 microsieverts per hour.

Elsewhere we have covered this quite well, but I will include a few of the facts here. Radium's most stable isotope, used in horology, has a half life of 1601 years. It doesn't glow after awhile because the Zinc Sulfide has degraded. Adding Zinc Sulfide does not make it glow again, as I had theorized earlier. The body sees Radium as Calcium, and imports it into the bones, leaving the exposed person with the terrible ache of Radium sickness, that sometimes doesn't show symptoms for years. The Alpha particles exit the watch case through the front, and very little, if any, goes out the back, being blocked by the dial and movt. I checked quite a few watches for this.

The dose is small, and concentrated to a small area. Full body doses are of course, more toxic, and standards are based on this. 

After much thought on the matter, I decided a few years ago to not ever strip Radium from dials or hands ever again, and I believe this is a good idea. Contamination is almost assured, and ingestion of any particles could cause some serious health issues. 

Additionally, I plan to take this up with my Doctor and radiologist at some point, and see what they think. 

Reverend Rob
Posted December 26, 2014 - 9:12am

Just a useful comparison, here. This is a quote from an ad discussing radiation doses for astronauts en route to Mars in an article dating to May, 2013, in 'New Scientist', by Lisa Grossman.

"NASA currently limits an astronaut's acceptable radiation dose to a 3 per cent risk of exposure-induced death from cancer over a lifetime. That amounts to 0.6 to 1 sieverts for women and 0.8 to 1.2 sieverts for men, assuming these individuals have never smoked and are between 30 and 60 years old."

One sievert is one million micro-sieverts. 

Posted December 26, 2014 - 8:03pm

Boy, I should already be dead... I have stripped and relumed over a hundred pairs of hands and at least ten or so dials. I use the proper protection of a filtered mask but that is all and I know the radium powder floats in my work shop.

I have been very fortunate in working with it and will probably continue to do so until I die, hopefully from old age and not raium poisining.


Geoff Baker
Posted December 27, 2014 - 5:49am

 A red spot, about 6mm in circumference, maybe a 1/4", on my left wrist, right smack dab under where I wear a watch (yeah, I'm old school, I still wear a watch). "Better have Dr. C look at it" said my wife the nurse. Dr. C is the dermatology doctor she was working for at the time. 

"Hmmm, better take that off" said Dr C a day or two later. She cut it off and cauterized the wound, The lab results were back just a couple days later, Sqamous Cell, malignant but once completely removed not a worrisome event.

Now it's just a teensy little scar, barely noticeable but I couldn't wear a watch for what seemed like a month and now I can't get those dials out of my head. I know, I know, highly unlikely that they caused that little spot but I just can't get 'em out of my head now.....


Reverend Rob
Posted December 27, 2014 - 10:19am


It would take 60 years to match the astronaut's 3 percent acceptable dose, and it is not body wide. That would be if the dial and hands were pressed against your wrist constantly. Literally nothing escapes the rear of the watch. The biggest risk is from ingestion, and having the particles absorbed into the body. 

I have stripped dials and hands, and been quite surprised at the amount of contamination that resulted. I've tossed out benchmats, chunks of Rodico, brushes, etc. The worst was the big car clock, it had a lot of Radium paint on it. 

I think it is important to be aware of what we are handling and to take precautions. Since the risk is relatively small, I don't think the watches themselves pose any real risk, it is the flaking or scraping of the paint and possible ingestion, whether by inhalation or otherwise. I rolled up all the debris into balls of Rodico and tossed them. That said, I won't be re-luming any old Radium dials from now on, unless it is to overpaint them with small amounts of new lume, which works ok.