how do you use a black light properly? - I don't completely understand how to examine possibly relumed dials with it. Is there any guide? (I do understand that if the reflection on the hands is brighter than on the dial, the hands may be re-lumed, but how can you check if dial and hands have been resumed at the same time?)

 

1. Turn it on
2. Point it at a watch dial
3. See what you see

 

I like to aim my black light at old concert t-shirts and heavy metal band posters from the 70's and 80's.

 

I prefer to use mine in motel rooms. Never know what you'll find!

 

First thing is that tritium will light up under UV. Lots of other material used to relume dials won't. It's a good check, but not definitive. If you can get up close with uv and loupe, you can see a lot of detail that may help...

 

On a Rolex dial that has be re-finished you can often see the new lacquer coating just stop short of the dials text - you end up with a Lasso around the text area. Like oddboy says, a good check but not definitive.

 

@oddboy makes a good point here: this is particularly true for military/older watches where the luminous material was radium. You can tell what if such watches have been relumed based on this.

Here are my two WWW watches - a Record and a Buren Grand Prix. They both originally came with radium. Depending on repair work though, it is possible hands and dial lume plots get relumed so further issue wear is possible.



Under UV/black light, this image becomes interesting:



The radium lume dots on the Record only glow under light and are very dull, and you can see that there is some extra luminous material on the minute hand. Who ever did it was quite sympathetic in only repairing as much as was needed and to come close to the same colour as well. The Buren on the other hand is almost like a Christmas tree with different lume intensities between the hands and dots, suggesting multiple repairs and lume materials, and the dust on the bottom probably comes from the hand that is missing it.

 

That's a man who has lived through the times....

 

And still having UV Flashbacks

 

I wouldn't if I was going to sleep in the room.
Ignorance is a bliss

 

but how can you tell if something has been resumed - resumed with either tritium or lumina or still has the factory original tritium lume?

 

Luminova will glow brighter. If you put the watch under a blacklight and it has a tritium dial with luminova hands for example, the hands will glow brighter and you’ll easily be able to tell they don’t match.