Luminous Dials on WW1 Officer's Trench Watches

Luminous Dials on WW1 Officer's Trench WatchesSome vintage watches, especially military watches, had the numerals and hands on the dial
made luminous or "glow in the dark" by painting them with luminous paint.
This paint was not like the luminous compounds used in todays watches; it was made
with a mixture of radium, which emits radioactivity, and zinc sulphide, which
"fluoresces" (glows
brightly) when hit by the radiation from the radium. This paint glowed all
the time, day and night, without needing exposure to sunlight,
and continued to glow for years on end.
However, after some time, maybe twenty to fifty years, the zinc sulfide is worn out or
destroyed by the radiation from the radium,
so the paint no longer glows in the dark - but the radium is still there emitting radiation.
Luminous radium paint on dials was first used around 1910, before the dangers of
radioactivity were fully understood. Although health problems in workers using radium
paints were noticed in the late 1920s, radium paint continued to be used up until
about 1950. If your watch was made before 1950, and has thick
paint, often off-white or yellowish, on the hands or dial numerals, the likelihood is
that the paint was made with radium, even if it no longer glows in the dark at all.
The half-life of radium-226 is about 1,620 years, so over the 100 or so years since
a watch dial was painted with luminous paint, the radium will have decayed about 4%.
Paint that was made with radium 100 years ago will
still be 96% as radioactive today as the day it was made, even if it no longer glows in the dark. Radium and its fission decay products (such as radon-222 gas) have the potential to cause various health
risks, and therefore watches with this paint should be handled carefully and in ways to minimize these risks.There is no need to panic if you have such a watch. They are reasonably safe to
wear on a once-in-a-while basis, but it probably would not be sensible to wear it all the time, i.e. every day, and certainly don't
sleep in it, or keep it on your bedside table. The more significant danger occurs when
working on such a watch, and one should be particularly careful not to breathe in any of
the paint or its dust. The best way to make sure that there is no risk is to have the
radium based paint removed and replaced by a paint that looks the same but is not radioactive.
Naturally this needs to be done by someone who knows what they are doing, so don't try
this at home! However, you also need to be careful that you are not damaging the authenticity of the watch by having this done. I have had an Omega dial where about half the luminous paint had flaked off restored, and now it looks much better than it did before, and the paint reproduces the old paint very well so you wouldn't know that it had been replaced. But the watch shown here is now back from from being restored and the dial painter has used a modern super-lume paint which really doesn't look like the old paint, so it has changed the look of the watch from an old-but-genuine specimen to being a very "clean" looking watch that has obviously been restored. I personally would have liked to keep the "old" look to it. So you need to think carefully before having this work done, and make sure the dial painter can reproduce the authentic look of the watch.The picture on the left shows one of my watches, a black dial trench watch which has
radium paint on the hands and numerals. As you can see, the thick yellowish paint is
quite distinctive against the fine white details of the enamelled dial. This
is typical of radium luminised dials, and should enable you to easily recognise one. I
guess that they made the paint by mixing the radium and zinc sulphide into a varnish or laquer, which
was applied quite thickly to get a good level of luminosity, making it difficult to produce fine detail.
You can see some of the paint has
flaked away from the enamel dial, particularly on the 9, just like a thick varnish would.
Further information for persons working with watches that have this type of luminous paint
on the hands and dials can be found in a UK Health and Safety Executive paper "Hazards from luminised timepieces in watch/clock repair" which can be found by a web search for this title.
I bought a radiation detector so that I can test my own watches for radium based
luminous paint. I am glad that I did - the first watch that I tried it on, the same black dial
trench watch with plenty of luminous paint left on the dial, sent it beserk, as you can see below.
I am planning to get the dial refinished to remove the luminous paint before I wear it. It seems
a shame to remove the historic paint that has been there for so long, but having heard
the frantic reaction of the radiation detector once it gets anywhere near the watch, I don't feel that
I have any choice on health grounds. I now offer a service to test your watch
for radiation, including a certificate stating what I find. This would be useful for
your own peace of mind, or if you are thinking of selling your watch, especially if
you have had the dial repainted to remove the radium. If you are interested in this service, please
drop me a line.
The first picture shows the radiation detector reading 0.14 micro sievert per hour
background level, which is pretty normal, and the alarm level set by the factory at
0.3 micro sievert per hour. The second picture shows the effect of putting the watch
next to the detector: the level jumps to 1.92 micro sievert per
hour and the audible alarm goes beserk. In the manual accompanying the detector, it says
". . . if a dose rate of more than 1.20 micro sievert per hour
is displayed, it is necessary to leave the zone urgently . . ." I certainly
won't be wearing this watch until the luminous paint has been removed, and I will be
treating it pretty cautiously in the meantime!I hope you have found this guide helpful. If you have then I would be grateful if you would register a vote for it. If
you haven't found it helpful for some reason, or if you think that there is something wrong or that could be
improved, then please let me know. Thanks! Regards - David

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