What is GTLS? (Gaseous Tritium Light Source)

Are you wondering what GTLS is?

Here is everything you need to know about the light source illuminating Nite Watches and leaving other watches in the dark.

GTLS is a unique highly specialised technology that uses a combination of tritium and phosphors to create visible light. As a cold light source, it requires no external electrical energy and is used for numerous applications such as emergency exit signs, military equipment, kit markers, compasses and wristwatches. It is a completely self powered, cold light source.

Tritium, also known as super heavy hydrogen, was first discovered by Ernest Rutherford, ML Oliphant and Paul Harteck in 1934. It is the third isotope of hydrogen and is mainly manufactured for industrial purposes. Tritium emits electrons through beta decay and when these electrons interact with a phosphorous material, a fluorescent light is created that can last between 10 and 20 years. When this tritium powered illumination is sealed inside a glass tube, it is known as a GTLS which are up to 100 times brighter over a long period than any comparable technology.

GTLS in Watches

GTLS is installed in watches intended for use during activities where reading the time in the dark is essential such as diving, military operations, security and law enforcement. However, being able to tell the time in the dark is generally a highly desirable feature to have in a watch.

The production of these small vials requires precision technology as they are produced as long cyclindrical glass capillaries lined with phosphorescent material. They are then filled and pressurised by a machine with gaseous tritium and sliced into segments by a laser beam to seal them hermetically.

Inside the vial, the electrons emitted by the tritium gas excites the phosphor to give off the cold continuous light. From the moment the vial is filled, the tritium begins to deteriorate giving off beta radiation (electrons) with a half life of 12.3 years. The tritium activity will be at its fullest when it has just been made and over many years this activity slows down causing the brightness to dim. If the vials are broken, the tritium will slowly disperse and oxidise.

Depending on how many millicuries of tritium is used in each watch; the GTLS is given a rating. For example many of our models feature T25 GTLS, such as the MX10, whereas our first HAWK model features T100 GTLS requiring bigger glass vials and is therefore much brighter.

Depending on the type of phosphorescent material used, GTLS can be created in different colours. Green is always the preferred colour as the human eye perceives green as the brightest. Blue GTLS, which is 60% as bright as green, is often used in diving watches as it remains visible at up to 60m/187 feet in depth – longer or deeper than any other colour.

We use state of the art GTLS by mb-microtec – the world’s leading manufacturer of tritium light sources.

Key facts about GTLS

  • GTLS technology does not require sunlight or any form of external power source in order to operate
  • GTLS are completely self contained pressurised laser sealed glass tubes
  • The illumination is permanently working and will operate without the pressing of buttons and does not need to be turned on
  • It is not possible to see the glow of a GTLS in daylight they will only be visible in half light or full darkness
  • Optimum visibility of GTLS occurs when the eyes are fully adjusted to the dark
  • Green GTLS are the most visible to the human eye and are also the brightest
  • Blue GTLS is 60% as bright as Green and Orange GTLS is 40% as bright as Green
  • Watches images shown on the Nite website will appear to have brighter GTLS than actual watches because of the visual size of the images
  • GTLS can be as small as 0.5mm in diameter and 2.5mm in length
  • GTLS will glow for up to 25 years. After 12.3 years the glow will only be half as bright compared to when the GTLS were first pressurised and sealed
  • If a GTLS breaks it will it will stop glowing but can be replaced
  • Watches that use super luminova or phosphorous paints for illumination require charging by light and may initially appear brighter and larger than GTLS but will fade to nothing in 1 and 4 hours
  • GTLS are a completely safe and reliable form of illumination

Check out our entire collection of illuminating watches by visiting our Store page