Reply
Thread Tools Display Modes
#1
Old 08-14-2006, 11:49 AM
Suspended
Join Date: Mar 2002
Posts: 18,476
What Makes Luminous watch hands Glow?

I know they don't use radium anymore (too dangerous). So what substance is used today? My watcg has luminous hands, but the glow is pretty faint-you can make it out at night, but it is by no means very bright. Are non-radioactive materials used?
#2
Old 08-14-2006, 11:57 AM
BANNED
Join Date: May 2000
Location: Houston, TX
Posts: 14,654
Tritium.

Good explanation here . (PDF)
#3
Old 08-14-2006, 11:58 AM
Charter Member
Join Date: Jan 2003
Location: Richmond, VA
Posts: 22,536
There are a few types. Inexpensive watches use phosphorescent materials which "charge" up in bright light then continue to glow for some time in the dark. Others use tritium, a radioactive alpha emitter. These alpha particles are made to excite a fluorescent material which glows; since alpha particles are easily blocked by even a single sheet of paper there is no significant exposure. Another, expensive, option is Luminox. I'm not sure exactly how it works since the page doesn't give out many details--proprietary info, I imagine. They call them "self-powered micro gas lights", whatever that means.
#4
Old 08-14-2006, 12:03 PM
Guest
Join Date: Oct 2000
Location: Yes
Posts: 20,333
Quote:
Originally Posted by Q.E.D.
Inexpensive watches use phosphorescent materials which "charge" up in bright light then continue to glow for some time in the dark.
Such as luminescent, doped Calcium sulfide
#5
Old 08-14-2006, 12:19 PM
Guest
Join Date: Sep 1999
Location: 221B Baker st. Colorado
Posts: 4,056
Quote:
Originally Posted by Q.E.D.
Others use tritium, a radioactive alpha emitter. Another, expensive, option is Luminox. I'm not sure exactly how it works since the page doesn't give out many details--proprietary info, I imagine. They call them "self-powered micro gas lights", whatever that means.
Luminox uses tritium (it's a gas, so "self-powered micro gas lights" is marketing)

Luminox is the brightest watch I've seen, bright enough to cast shadows in a dark room, where some of the other tritium watches are just barely visible at night. Could be the OP has a S&W, I wasn't impressed with their glowieness
#6
Old 08-14-2006, 12:31 PM
Guest
Join Date: Aug 2006
Posts: 60
Quote:
Originally Posted by Q.E.D.
There are a few types. Inexpensive watches use phosphorescent materials which "charge" up in bright light then continue to glow for some time in the dark. Others use tritium, a radioactive alpha emitter. These alpha particles are made to excite a fluorescent material which glows; since alpha particles are easily blocked by even a single sheet of paper there is no significant exposure. Another, expensive, option is Luminox. I'm not sure exactly how it works since the page doesn't give out many details--proprietary info, I imagine. They call them "self-powered micro gas lights", whatever that means.
So presumably if you wanted to tell phosphorescent from tritium, you could tell it from whether it was a constant glow or a fade proportional to the amount of time since light exposure?
#7
Old 08-14-2006, 12:37 PM
Charter Member
Join Date: Jun 2000
Location: Alaska!
Posts: 8,184
Quote:
Originally Posted by Placid Liver
So presumably if you wanted to tell phosphorescent from tritium, you could tell it from whether it was a constant glow or a fade proportional to the amount of time since light exposure?
Or just read the back of the watch.
#8
Old 08-14-2006, 12:46 PM
Guest
Join Date: Sep 1999
Location: 221B Baker st. Colorado
Posts: 4,056
Quote:
Originally Posted by Placid Liver
So presumably if you wanted to tell phosphorescent from tritium, you could tell it from whether it was a constant glow or a fade proportional to the amount of time since light exposure?
That is indeed a way as tritium won't fade overnight
Or the dial may have a "T" on it somewhere (bottom of this dial "T swiss made T") or an "H3" (here )
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 02:16 AM.

Send questions for Cecil Adams to: [email protected]

Send comments about this website to:

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Copyright 2018 STM Reader, LLC.

Copyright © 2017
Best Topics: cough drops diarrhea buy dolphins cantor's diagonal salon sucks sink stops vladimir harkonnen strippper names excessive absence orin incandenza mix tequila with fax max danny thomas glass coffee table trivial pursuit xbox one answers smell gas in my house do elephants have knees songs similar to hey there delilah what is riding dirty michelin pax tires for sale can you track a fedex truck traditional mexican wedding rings how much does cosmetic mole removal cost does chicken bouillon go bad certified mail return to sender unclaimed