![]() Radium atoms decay into Radon, which is a gas at room temperature, by emitting alpha and gamma particles as radiation. ![]() Radium luminous paint gives off radon gas which also emits alpha particles when it decays and which, if inhaled, can cause lung cancer, so watches with radioluminescent paint should be kept in a well ventilated space or a sealed container.Degraded paint is more of a problem with very early luminous watches due to their age and the amount of radioactive material used in the paint. If the watch is opened and dust or other decay products are inhaled and enter the lungs, alpha radiation can cause lung cancer. Radiation damage over the years makes radioluminescent paint very brittle and it easily breaks into flakes and dust.Note that very old watches from around the World War One era have relatively large amounts of radioactive material in their paint and give off much stronger radiation than later luminous watches. However, the wearer and those around will be exposed to some extra gamma radiation of varying amounts. Wearing a watch with radioactive luminous paint is not particularly dangerous.The alpha particles are stopped by the case or the crystal, but the gamma radiation easily passes through the case. Radium and other materials used to make radioluminescent paint decay by emitting alpha and gamma particles as radiation.These can be broadly summed up as follows, but for the full detail please read the rest of this page. The risk from these hazards is relatively small, but you should be aware of them. There are several sources of hazards from radioluminescent paint, all of which are due to radiation given off by radioactive decay of elements within the paint and the subsequent decay of the resulting elements. My view is that it is not necessary to avoid watches with radium paint altogether, but it is necessary to understand it and the risks it can pose, particularly if you are going to collect or work on old watches that may have this type of paint. However, here I can take a more measured view of the dangers without being flamed. Radium based luminous paint was banned in the 1960s on health grounds, when attitudes to risk were less precautionary than they are now, so to say that radium paint is less dangerous than mobile phones, which clearly haven't been banned, is plain wrong and highly irresponsible.Ĭaution is rarely a bad thing, but it doesn't get you much kudos on internet forums. It is safe to say that those who don't know what the panic is all about simply don't understand the subject and should be ignored. I even read a comment that the radiation from radium luminous paint is less dangerous than a mobile phone. If you “consult” internet watch forums you will find that some some people get very exercised about the dangers of radium paint, while others don't know what the panic is all about. Note that old radium paint no longer glows in the dark because the radiation burns out the fluorescent material over a short time, about 5 years, but the radium has a radioactive half life of about 1,600 years and therefore remains very nearly as radioactive as when the paint was new. These are called radioluminescent paints because their luminosity comes from radioactivity stimulating a fluorescent material to emit light. There are broadly two types of luminous paint that a watch collector might encounter, modern luminous substances that are quite safe, or earlier paints based on radioactive materials such as radium that need to be treated with caution. Ever since military, and many civilian watches, have had luminous dials. This is discussed in more detail on my page about Trench Watches. Trench Watch with Radium Luminous Dial: Click to enlargeĭuring World War One it was quickly realised that a watch with luminous hands and numbers was essential for an officer in the trenches, it allowed the time to be checked in low light or in the dark without using a light that could have attracted a shot from an enemy sniper. ![]()
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