[time-nuts] Atomic Clocks: It is important that they keep good time, Part 1

[Majdi S. Abbas]

On Mon, Jan 07, 2019 at 02:21:07PM -0500, Bob Bownes wrote:
> 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.

	You might try International Dial Co -- they repaint watch dials; 
if they don't have the die for your dial, they might at least be able to
refer you to someone who does.

> 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...

	They're not surplus, and you can buy plenty of new sights and
sighting devices containing tritium.

	Generally speaking, an artifical sapphire tube is coated with
phosphor, and then filled with the gas.  When it's time to replace
the tube, you either replace the sight entirely, or in the case of
hybrid tritium/fiber optic systems like the ACOG, send it back to have
the manufacturer replace the tube, thus refurbishing the sight.

	Tritium isn't banned...but tritium lume has definitely fallen
out of favor.  I haven't seen any used in new products for about 20
years, and I'd be surprised if it's still made in any significant
quantity.  Watches, gun sights, and even magnetic compasses have moved
on to using the gaseous tritium sources.

	I don't think this is a bad thing.  It's much safer to handle,
without the risk of ingesting or inhaling a beta source.

	And radium is not something you want to handle (although I'd
possibly consider going over a radium dial or hands with modern lume --
more to help seal the old radium paint in, than to restore function,
although it will do that.  IMHO, the best option is still to have them 
professionally repainted.)

	The current generation of photoluminescent lumes are quite 
bright and long lasting after light exposure -- seriously consider 
having any old radium dials and hands stripped and repainted.  I had
a WWII watch dial that was over 4,000 cpm, with lots of visible lume
dust present.  Nice collectible, but not worth the health risks to 
keep original.  It's been refinished with modern materials.

	--msa