A note about safety

Compasses manufactured in the first half of the 20th century up until about 1965 may have luminous paint on the dials, needles or compass points. This paint will usually have a raised profile if applied on a flat surface,  but can also be found in embossed grooves such as lettering or numbers. It will tend to have a 'flat' look as opposed to 'glossy' appearance. It can be almost any color from a a very light greenish white or a brownish or dark red color.

The luminescent material may be radium paint, which is poisonous and radioactive. Do not open the capsules of these older compasses, as the radium paint may be very brittle with age, and may tend to flake and  become airborne. Do not allow children to handle these compasses. Wash your hands immediately after handling them.

As it decays, radium paint also gives off Radon gas which is a hazard in itself. Store radium-painted items in a well  ventilated area to prevent a buildup of Radon. Radon gas is itself radioactive, but it also decays into several other radioactive isotopes. A display case with radium-painted items in it may tend to accumulate a fine coating of radioactive dust, unless it is kept well ventilated.

The paint is generally considered harmless if it is "encapsulated" as in the case of a compass face which is encased in glass. If, for some reason,  you decide to take the compass apart, treat the interior of the compass like  radioactive material. Wear a dust mask, and wash your hands and clothes thoroughly after handling it, and dispose of any cleaning materials properly.  Don't breathe the dust or handle any scrapings. Better yet, don't disassemble  the compass.

Not all radium paint is encapsulated. Several of my compasses have radium paint in exposed areas.  The WW-II German compasses with the large "A" painted  on the cover have found to be 'hot' in exposed areas, including the "A" itself!.  Be very careful handling these compasses. I suggest wearing disposable gloves and discarding them and washing your hands afterward.

Don't assume that if the compass points don't glow anymore, that they are  'safe'. The paint was manufactured by mixing radium with zinc sulfide or another flourescing substance along with a glue binder. The flourescing substance emits light when struck by the radioactive particles. Exposure to light is not necessary to make the paint glow. This paint was used on many different  products made by many different companies until its use was banned. The  flourescing substance may have deteriorated over the years but it's unlikely  the radium has decayed. It's half-life is 1600 years.

  Here is a chart showing the half-lives of Uranium decay products (including radium). This is a logarithmic chart, meaning that the graduations represent larger intervals as you move to the right.

Another problem exists in that not all companies used pure radium in their luminescent preparations. Today it is difficult to tell exactly what you are dealing with. If you have any questions, you should have the item tested. Many hospital radiology departments will do this.

Today, new materials are used in compasses, wristwatches, aircraft instruments, etc.

Some of these are phosphors. These are *not* a radioactive materials. These materials has been used for many years in various 'glow in the dark' applications, including children's toys. It is the stuff that you 'charge' by exposing it to a bright light. The atoms of the various phosphors absorb the photons, and then slowly release them, creating the 'glow'. It is completely safe.

Another new material is a radioactive isotope of hydrogen called tritium. Tritium is a gas and has a half-life of 12.43 years. It decays into a stable non-radioactive form.  In commercial use, the gas is put in tiny vials of borosilicate glass that is internally coated with phosphor and sealed by a laser. These assemblies are referred to as radio-luminescent light sources, also known as Gaslights or Trasers. The vials can be made so small that they can be placed on compass needles and  cardinal points.

Unlike radium paint, tritium gas emits only low energy beta particles  (electrons) that are unable to penetrate the borosilicate glass vials.  This makes their use completely safe. The non-radioactive phosphors used today must be exposed to light or to some other energy source. Trasers glow  constantly by themselves, even in total darkness and require no energy source. Trasers are commonly made with green and yellow phosphors that can most easily  seen. Other colors include orange, red and blue.