please tell me what this means

[stevemulholland3]

on the bottom of the dial I have:
swiss T<25
i KNOW THE "T" STANDS FOR TRITIUM,BUT WHAT DOES THE "<25" STAND FOR?
THANKS IN ADVANCE,
STEVEN T. MULHOLLAND

[Spark]

Hi Steve,
Here is the answer "Swiss T<25" means that the watch is Swiss and contains a certain quantity of tritium that emits less than 925 MBq (25 mCi).
Cheers,

Mark.

[mike]

As Mark said "SWISS-T<25" indicates a tritium dial emitting less that 25 milicuries of radiation--Beta.

[SPACE-DWELLER]

You can read more about luminosity on this site.

Tritium was banned in 1998 and is a mildly radio-active material emitting beta waves. On watch dials it glows constantly via phospers bonded to the Tritium. Although Tritium is radio-active, it is not harmful on a watch since only small quantities are used and the beta wave activity cannot go past the crystal and watch case. In fact, it only takes a thin sheet of Aluminium to block Tritium radiation.

Tritium has a halflife of about 12,5 years, and after that it will (in most instances) not glow anymore. Tritium markers have also been known to degrade (discolour) by age. Some say UV rays a humidity play a role, it is said.

Here is a good article about luminosity.

[stevemulholland3]

thank you all,and I appreciate the quick responses.
cheers,
steve

[crimscrem]

Originally Posted by SPACE-DWELLER

You can read more about luminosity on this site.

Tritium was banned in 1998 and is a mildly radio-active material emitting beta waves. On watch dials it glows constantly via phospers bonded to the Tritium. Although Tritium is radio-active, it is not harmful on a watch since only small quantities are used and the beta wave activity cannot go past the crystal and watch case. In fact, it only takes a thin sheet of Aluminium to block Tritium radiation.

Tritium has a halflife of about 12,5 years, and after that it will (in most instances) not glow anymore. Tritium markers have also been known to degrade (discolour) by age. Some say UV rays a humidity play a role, it is said.

Here is a good article about luminosity.

So, what does one do when his watch no longer glows? Just live with it?

[armypilot]

Originally Posted by crimscrem

So, what does one do when his watch no longer glows? Just live with it?

You can have the dial relumed, replace the dial, or just leave that vintage dial alone and live with it.....I prefer the latter.

[Spark]

Originally Posted by armypilot

You can have the dial relumed, replace the dial, or just leave that vintage dial alone and live with it.....I prefer the latter.

+1

[mike]

Originally Posted by armypilot

You can have the dial relumed, replace the dial, or just leave that vintage dial alone and live with it.....I prefer the latter.

Me too. Depending on the reference and vintage the impact can be severe.

[JohnEaton]

Originally Posted by crimscrem

So, what does one do when his watch no longer glows? Just live with it?

Fill the watch with tritium gas and don't open the crown