How to identify a relume by UV light inspection?

SkunkPrince

There are two reasons lume won't lume. No more radiation, or the paint oxydizes. Tritium has a half-life of 25 years; couple that with oxydation, and you get nothing. That your UV source doesn't excite it bears this out.

The half-life of radium might as well be forever; almost always lack of lume is because of paint oxydation.

My personal experience with tritium gas tubes, about ten years is all you'll get between OMG IT'S A FLASHLIGHT to I can't see it glow any more.

My night vision is reaaaaaally good so I can see radium lume most of the time after dark adaptation. Depending on the paint, the results can be anywhere from "there's lume?" to I can read my 1910 alarm clock no sweat.

Glad you had fun with the black light but all of the results are idiosyncratic to the watches and doesn't really tell you much of a general nature.

Dan S

The excitation or lack of excitation of these dials by UV is not related to tritium; it's the response of the particular phosphor formulation to UV or visible light excitation.

Tritium was the power source originally intended to excite the phosphor. Tritiated polymer binder was formulated with phosphor particles (e.g. zinc sulfide) and other minor ingredients (e.g. pigment) to make the luminescent paint. When these watches were new, the plots were luminescent all the time, even in the total absence of UV or visible light excitation since the phosphor was excited by the radioactive decay of tritium. However, since tritium has decayed almost completely after several decades, the phosphor will no longer emit in the absence of external excitation by UV or visible light.

Thus, any emission you see upon UV/vis excitation of these dials comes from the phosphor directly, nothing to do with tritium. Some phosphor formulations have degraded chemically and no longer respond to UV excitation. Other formulations still respond to direct excitation but die off after a few seconds. Yet other formulations die off partially after a few seconds, and then have a residual emission for several minutes. Different manufacturers used different phosphor compounds and formulations, and even changed them over the years. Rolex, in particular, changed their formulation significantly over time, from the 60s to the 70s to the 80s. Thus, knowledgeable collectors are well aware of how Rolex phosphors made in different eras should respond to UV light, but they're not always eager to post this detailed information on public forums, for obvious reasons.

In the absence of this detailed knowledge, the most you can do is look for consistency between all of the lume on the dial and hands. Often you will see that one hand, or one marker responds differently, which gives away a relume. If the entire watch and hands have been relumed using paint that incorporates material recovered from old watches, then it will be quite difficult for you to detect the relume unless you have done tests on many similar watches.

SkunkPrince

Just to elaborate a bit on Dan's good explanation, if UV excites the lume and it persists an hour later, that is almost for sure a relume using Luminova or its Japanese equivalent, whose name I don't recall.

Foo2rama

Why is the freese101 watch not lighting up... I could have sworn they used vintage colored luminova...

Vintagewtchzilla

Also don’t forget that not every uv lamp uses same intensity and wave length.

Yes the freese one is disturbingly dead but i don’t know what basis is used as lume.

Davidt

I can't speak for vintage Rolex, but as long as the remaining paint/phosphor/tritium compound is still in good overall condition (I.e. Not degraded to green mush due to moisture ingress) vintage Omega tritium dials from the 60's/early 70's always exhibit glow when excited by an external source such as a flashlight in my experience.

This may be feint but in original Omega dials from this period it's always there.

Dan S

Rolex lume from certain time periods is completely dead, and from before that period it is strongly excited. The 5-digit dials shown by the OP aren't old enough to demonstrate these changes.

Dan S

The excitation or lack of excitation of these dials by UV is not related to tritium; it's the response of the particular phosphor formulation to UV or visible light excitation.

Tritium was the power source originally intended to excite the phosphor. Tritiated polymer binder was formulated with phosphor particles (e.g. zinc sulfide) and other minor ingredients (e.g. pigment) to make the luminescent paint. When these watches were new, the plots were luminescent all the time, even in the total absence of UV or visible light excitation since the phosphor was excited by the radioactive decay of tritium. However, since tritium has decayed almost completely after several decades, the phosphor will no longer emit in the absence of external excitation by UV or visible light.

Thus, any emission you see upon UV/vis excitation of these dials comes from the phosphor directly, nothing to do with tritium. Some phosphor formulations have degraded chemically and no longer respond to UV excitation. Other formulations still respond to direct excitation but die off after a few seconds. Yet other formulations die off partially after a few seconds, and then have a residual emission for several minutes. Different manufacturers used different phosphor compounds and formulations, and even changed them over the years. Rolex, in particular, changed their formulation significantly over time, from the 60s to the 70s to the 80s. Thus, knowledgeable collectors are well aware of how Rolex phosphors made in different eras should respond to UV light, but they're not always eager to post this detailed information on public forums, for obvious reasons.

In the absence of this detailed knowledge, the most you can do is look for consistency between all of the lume on the dial and hands. Often you will see that one hand, or one marker responds differently, which gives away a relume. If the entire watch and hands have been relumed using paint that incorporates material recovered from old watches, then it will be quite difficult for you to detect the relume unless you have done tests on many similar watches.