As a brand who sells both T25 and T100 Tritium illuminated watches, we often get asked what the difference is between the two options and which is better.

Firstly, what is Tritium illumination?

Tritium, also known as super-heavy hydrogen, emits electrons through beta decay and when these electrons interact with a phosphorous material, a fluorescent light is created that can last up to 20 years.

When this Tritium powered illumination is sealed inside a glass tube, it is known as a GTLS (Gaseous Tritium Light Source) which is up to 100 times brighter over a long period than any comparable technology.

To produce a GTLS vial, glass is lined with phosphorescent material, then filled and pressurised by a machine with gaseous tritium and sliced into segments by a laser beam to be sealed hermetically.

Inside the vial, the electrons emitted by the tritium gas excites the phosphor to give off the cold continuous light.

Tritium illumination is widely regarded as the World’s best and most reliable form of watch illumination available which is we choose to use it in every Nite watch.

So, what’s the difference between T25 and T100?

All watches that utilise Tritium illumination carry a “T” rating. This T rating refers to the total watch radiation content which is measured in millicuries. All watches with a T25 rating contain up to 25mCi of radiation content and similarly, watches with a T100 rating contain above 25mCi and up to 100mCi.

And therefore, the individual tubes in a T100 rated watch aren’t necessarily any brighter than those in a T25 watch, it just means that there is more Tritium content in the entire watch.

OK, so which is better?

The straight answer is… it is up to you.

Some people prefer T25. Some people prefer T100. Some people like both.

The T25 watches often offer a much more subtle glow and appearance. This is especially useful if you are trying to keep covert at night which is one of the reasons our field watch, the MX10, is T25 rated.

Meanwhile, the T100 watches offer maximum visibility in the dark, which is ideal if you are dependent on checking the time at a glance, such as in our dive watch, the Alpha series, which are all T100 rated.

We hope that has helped answer any questions you had about T25 vs T100 Tritium illumination, but if you do have any more questions then please do let us know by sending us an email to theteam@nitewatches.com, or giving us a call on 01202 487757 where we will be more than happy to discuss it in more detail with you.

You can also check out our collection of watches to see which illumination options you prefer.