Monday, November 2, 2020

With a half life of 1600 years, radium is here to stay


The other day, yet another vintage Rolex came in for repair. The original dial and hands were well preserved with a rather heavy and thick coating of luminous material. A perfect collectors’ example. However, this was a bit worrying as the 1930s luminous material was a mixture of phosphor and radium, and while the phosphor no longer glows, the radium is still as potent as it was 90 years ago.

Clearly before we proceeded with disassembly, we needed to measure the radioactivity level, and the ensuing reading was undoubtedly concerning. 4 micro-Sieverts per hour, about 6 times more than the safe level. I called the customer to let him know that while I have no problem repairing the watch, a restoration would make little sense as, if he were to wear the watch for 8 hours a day, he would be exposed to the same levels of radiation as flight attendants or nurses working in a hospital.

There are two problems with radium. One is the radiation itself and secondly the creation of radon gas. I am not an expert in this field, but it is the radon gas that is far more harmful than the radiation which comes off the watch dial. A single World War II military watch with a heavy coating of radium can blast 20 ┬ÁSv/hour or more, which 40 times the safe level. The same goes for military Panerai watches, and if you have a collection of a few stored in a safe deposit box you are protecting yourself from radiation, but not radon gas. According to well documented medical research, radon gas is the second leading cause of lung cancer, with smoking being the first. Radioactive substances are invisible killers and should be taken seriously. If you have a watch with radium dial, and you come in, I would be more than happy to assist. If you wish to dispose of it, call the specialists:

Here is an interesting article on recent findings of radium in the Swiss watchmaking industry.
"Nearly 1,000 watchmaking buildings and workshops in Switzerland could be contaminated by radium, a radioactive element that was used to add luminescence to watch dials and hands until the 1960s."

And here is the photo of the radiation level of the watch we recently restored. Safe to wear! You can find the link to the entire restoration here:
Finally a whole box of railway pocket watches, again well within a safe level. Bottom line is collect railway pocket watches and avoid military. 

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