Radioactive watch: Before we begin, please remember that radium is a dangerously radioactive substance and repeated exposure is very dangerous. Horrible things happened to watchmakers who used the material in painting hands and numerals and devasting diseases like jaw and stomach cancer often plagued assembly-line workers in the days when radium was still in popular use.
Read the book Radium Girls for more info on this topic.
Radium was commonly used on many watches built during World War I. These watches, called Trench Watches, had luminous faces for reading in the dark trenches along both sides of the battlefield and often featured big, bold numerals and hands to maximize the radium’s surface area.
Radium became more popular in the intervening years and almost every watch between 1917 and the early 1970s used a form of radium paint.
According to the EPA, radioactive antiques are still highly dangerous and were made more so by safety failures in the painting process:
Radium is highly radioactive. It emits alpha, beta, and gamma radiation. If it is inhaled or swallowed, radium is dangerous because there is no shielding inside the body. If radium is ingested or inhaled, the radiation emitted by the radionuclide can interact with cells and damage them. During the production of radium dials, many workers who painted clock or instrument dials with radium developed cancer. To create fine tips on their paint brushes for small surfaces, many radium dial painters licked the bristles of their paintbrushes. In doing this, they often swallowed some of the radioactive paint. In the body, radium acts similar to calcium, so the radium that workers ingested was deposited into their bones. Many of these workers developed bone cancer, usually in their jaws. Eventually, scientists and medical professionals realized that these workers’ illnesses were being caused by internal contamination from the radium they ingested.
What does a radioactive watch look like?
A radium watch may still be radioactive years after manufacture. Radium retains its fluorescence for a long time and many radium dials might still have a charge in them. They tend to “burn” over time, turning the hands a dull brown. Plastic crystals can often exhibit a burn-in from the paint.
Radium-based paint was banned in the 1960s and all of the paint was phased out a decade later. The easiest way to tell if a watch is radioactive is to pick up a simple Geiger counter. This will tell you definitively if a piece is radioactive. Further, here are some rules of thumb to tell whether or not your watch is radioactive.
- If it was made prior to the 1960s then it probably used radium.
- In the early 1960s some watches were marked T (T- SWISS MADE -T appeared on the bottom edge of the dial.) This kind of watch used tritium. Watches with the R marking still used radium.
- Alphahands writes: Rolex (and Tudor) timepieces will have additional symbols to indicate different levels of radium. The “exclamation point”, where a small dot is below the index marker at 6 o’clock (first seen in 1962), indicates that the piece is following Atomic Energy Commission regulations from 1960 and has lower radiation levels. The underline on the dial (seen starting in 1963) was used to indicate still lower radiation levels, in line with <25 millicuries of tritium.
- Miltiary watches used starker symobosl like the nuclear triangle and to signal some radioactivity.
How do radium watches work?
Old radium watches are constantly radioactive if the paint is still extant on the face. That said, watches only glowed when the radium was mixed with zinc sulphide or another fluorescent compound. Many of these watches are probably burnt out because the fluorescent compound is no longer light-emitting.
Further, the radium is often covered in varnish which becomes weak and will flake off hands and numerals. These paint flakes are equally dangerous and care should be taken not to breathe them in.
How to fix a radium clock or watch
Do not touch or change a radium dial. If you want to replace your hands or face, the best bet is to have a repairer repaint the dial with nonradioactive paint. That said, you probably shouldn’t touch a radioactive dial at all as many collectors prefer the patina and changes that these timepieces go through over time. Again, these items are very dangerous, and constant exposure is dangerous.
A good watchmaker can remove the old radium paint and replace it with modern luminescent substances, allowing an old trench watch to have a second life. Do not attempt this yourself as the material is still radioactive and getting the right look and feel is very difficult.
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About the Author / Author Expertise & Authority
John Biggs: I live in Brooklyn, NY and write about technology, security, gadgets, gear, wristwatches, and the Internet. After spending four years as an IT programmer, I switched gears and became a full-time journalist. My work has appeared in the New York Times, Laptop, PC Upgrade, Gizmodo, Men’s Health, InSync, Popular Science, and I’ve written a book called Marie Antoinette’s Watch about the most famous and mysterious watch ever made. I am the former East Coast Editor of TechCrunch.com.