How safe are our collections?

[G4YVM David]

Whilst i have seen old instruments I have never experienced the glow in the dark effect and it is pretty close to the top of my bucket list now. Must visit some aerojumbles!

[Jon_G4MDC]

Interesting to read the wiki on Radium dials. A 1960s Westclox Big Ben was very impressive in the dark.

I had no idea that one that no longer works is probably still as radioactive as when first made. Zinc sulphide produced the light and that is what degrades not the radium.

[G6Tanuki]

Originally Posted by G4YVM David

Whilst i have seen old instruments I have never experienced the glow in the dark effect and it is pretty close to the top of my bucket list now. Must visit some aerojumbles!

The glowy dials tend to fade rather significantly with age. I've got a couple of WWII-vintage ones here which are highly 'active' but the phosphor has gone the same way as that in Magic Eyes and there's no longer any significant glow to be seen.

[GMB]

Originally Posted by suebutcher

Was thorium the radioactive material in the gas regulator tubes, or something else? Are valves like the 0A2 going to stop working eventually even if they're unused?

There are various materials listed as used. Not sure about OA2 (must check one). They won't stop working in general, but the strike voltage will go up. This kind of thing was mainly done for specialist gas-filled tubes e.g. used for radar, but it may have been done for ordinary voltage stabilisers to make them more predictable.

BTW do not assume that alpha emitters do not emit gamma too. You get secondary nuclear reactions so the end result is often a bit of everything!

Old aircraft instruments are often very radioactive. The worst I have met is the BABS indicator. If you don't have a radiation meter then you can check by shining UV light onto anything that has that characteristic brown/yellow coloured paint. If it does NOT glow then assume the worst!
Later instruments had the phosphors but no radioactive material so needed a UV illuminator to work.

Some of the army sets were bad too. WS62 is very bad!

[turretslug]

I'd heard that the heavy alpha emission of said paint actually fries the luminescent component into inactivity- in other words, be very wary of any brown/yellow paint that doesn't glow.

[G4YVM David]

Originally Posted by turretslug

I'd heard that the heavy alpha emission of said paint actually fries the luminescent component into inactivity- in other words, be very wary of any brown/yellow paint that doesn't glow.

Eek. Maybe I will steer clear at jumbles!!