On Mon, 10 May 2021 11:15:02 -0500, AMuzi wrote:

On 5/10/2021 9:44 AM, Tom Kunich wrote:

The radioactive paint on the dials of my Seiko has long ago worn off.

Actual radium was dropped a very long time ago (mid-1950s).
It doesn't 'wear off' under your crystal. With a half life
of a few thousand years it's pretty dependable as most
products go.

The 'modern' chemicals only glow for 8~12 years. Gas glow
only lasts until the battery is out.

There's also phosphorescent paints:
https://www.seikowatches.com/us-en/customerservice/faq/general-information-9
1. Longer output duration
It glows at its full brightness after a brief
exposure to sunlight or artificial light (more
than 500lux) for about 10 minutes. The light
lasts for about 3-5 hours in the dark, which
is more than 10 times longer than conventional
luminous paint.

However, I have a partial workaround. I sometimes carry a UV
flashlight.
https://www.ebay.com/sch/i.html?_nkw=uv+flashlight&_sacat=0&rt=nc&LH_PrefLo c=1
(Get the model that has a single UV LED, not the models with an array
of small UL LEDs). It really lights up any kind of phosphorescent
(long glow time) or fluorescent (very short glow time) paint, powder,
or additive. Works well on luminous watch dials. Also, with a
suitable dye, UV flashlights are great for finding oil leaks:
https://www.ebay.com/itm/182246980328

--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558