Interesting. I was wondering this as well now that time-nuts has gotten me into collecting vintage (pre WWII) chronographs. Some are radium, some not, most are in need of a good repaint either way.
But I do know that tritium gun sights are also a thing. Are those all mil-surplus or using some secret source of tritium paint... BTW, latest acquisition in the Vintage watch collection is a 1916 Waltham, made nearby, with still a local watch shop specializing in them. Looking forward to it's arrival. On Mon, Jan 7, 2019 at 1:48 PM Warren Kumari <war...@kumari.net> wrote: > On Fri, Jan 4, 2019 at 6:59 PM Steve Allen <s...@ucolick.org> wrote: > > > On Fri 2019-01-04T17:05:21-0500 paul swed hath writ: > > > Ed agree with your coment that a 30 or greater year old led may be > > dimming. > > > > Not nearly as much as an entirely different clock illumination: > > radium watch dial paint > > I remember my mom's wind-up travel clock glowing brightly. 50 years > > later there is nothing. > > > > I used to have a Rolex submariner with a tritium paint based dial -- I > really loved the watch, but the tritium had sufficiently decayed that it > would no longer fluoresce - this didn't affect the utility, but made me > sad.... It was made in ~1989 and marked SWISS T < 25 for "less than 25 > milliCurie" (apparently much less, they started out at ~5 milliCurie). In > ~2016, the tritium would have decayed to ~1 milliCurie. Tritium paint is > (apparently) no longer legal in the USA, but when I was in Hong Kong I > found someone who had "new" paint, and willing to repaint the face -- > unfortunately I didn't have time on that trip to have it done, and when I > went back a few months later the shop had closed down... > > There is a (apparently) a group of watch dial enthusiasts who get a > specific brand of tritium based exit sign which has tritium paint embedded > in the plastic (most tritium exit signs are the small gas capsules > instead), grind them up and then extract the paint from the ground plastic > using solvents. I briefly toyed with this idea before deciding this was bad > mojo and sold the watch... > > > > I brought it into the lab just to check that > > it is still radioactive (wouldn't want to have lost that radium > > somewhere). It's the zinc sulfide crystals, the radiation damages > > them and they stop producing light. > > > > Hmmmm. I wonder if that is actually what happens with the tritium paint - > the dial I had would *just* have a visible glow if I had it in a perfectly > dark room and let my eyes adjust for a while. If the tritium level had > decayed from 5 milliCurie to 1 milliCurie I would have guessed that the > glow should just have been 1/5th of original. The dial would still > fluoresce nicely under UV, so I'm not sure what that means... > > W > > > > -- > > Steve Allen <s...@ucolick.org> WGS-84 > (GPS) > > UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat > > +36.99855 > > 1156 High Street Voice: +1 831 459 3046 Lng > > -122.06015 > > Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > > > -- > I don't think the execution is relevant when it was obviously a bad idea in > the first place. > This is like putting rabid weasels in your pants, and later expressing > regret at having chosen those particular rabid weasels and that pair of > pants. > ---maf > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.