Have you ever thought about what substance is used to make the numbers or index markers and hands of a watch glow at night? Well I have and here is what I’ve discovered.
In 1898 Marie and Pierre Curie discovered the element Radium. By 1914 an American company called the United States Radium Company was selling a paint infused with radium. At that time the danger posed by the radium was not well understood. Of course, radium is highly radioactive, emitting alpha, beta, and gamma radiation — the effects of which are particularly deleterious if inhaled or ingested since there is no shielding within the body. Indeed, the body treats radium as it does calcium, storing it in bone where it may cause bone degeneration and cancer.
After 1968 radium was no longer used in watch dials. Nowadays, many watch companies use various types of phosphorescent pigments, otherwise known as lume. These pigments operate like a rechargeable light battery. After sufficient exposure to sunlight, fluorescent, ultraviolet (blacklight), LED, incandescent and/or other light sources, they glow in the dark for hours. The most common brand is called Super-LumiNova manufactured by the Swiss company, LumiNova AG. Seiko uses it’s own formulation called LumiBritre. Most importantly theses pigments are totally safe and emit no radiation.
A few watch companies equip their watches with tritium lighting. This form of radio luminescence is made using glass tubes with a phosphor layer in them and tritium gas inside the tube. Such a tube is known as a "gaseous tritium light source" (GTLS), or beta light (since the tritium undergoes beta decay), or tritium lamp. Alhough these watches contain a radioactive substance, it is currently believed that this form of self-powered lighting does not pose a significant health concern.
There are numerous online sources which can easily provide more information on other materials used in the watch industry.
In 1898 Marie and Pierre Curie discovered the element Radium. By 1914 an American company called the United States Radium Company was selling a paint infused with radium. At that time the danger posed by the radium was not well understood. Of course, radium is highly radioactive, emitting alpha, beta, and gamma radiation — the effects of which are particularly deleterious if inhaled or ingested since there is no shielding within the body. Indeed, the body treats radium as it does calcium, storing it in bone where it may cause bone degeneration and cancer.
After 1968 radium was no longer used in watch dials. Nowadays, many watch companies use various types of phosphorescent pigments, otherwise known as lume. These pigments operate like a rechargeable light battery. After sufficient exposure to sunlight, fluorescent, ultraviolet (blacklight), LED, incandescent and/or other light sources, they glow in the dark for hours. The most common brand is called Super-LumiNova manufactured by the Swiss company, LumiNova AG. Seiko uses it’s own formulation called LumiBritre. Most importantly theses pigments are totally safe and emit no radiation.
A few watch companies equip their watches with tritium lighting. This form of radio luminescence is made using glass tubes with a phosphor layer in them and tritium gas inside the tube. Such a tube is known as a "gaseous tritium light source" (GTLS), or beta light (since the tritium undergoes beta decay), or tritium lamp. Alhough these watches contain a radioactive substance, it is currently believed that this form of self-powered lighting does not pose a significant health concern.
There are numerous online sources which can easily provide more information on other materials used in the watch industry.