Since he previously hadn’t detected anything (when the instrument was closed) he was sure that alpha particles were causing that large amout of “clicks”, since alpha particles may be completely stopped by a sheet of paper (in his case, by the glass of the instruments), beta particles by aluminum shielding while gamma rays can’t be stopped and can penetrate deeply unless stopped by a thick layer of lead.
#Radium dials portable#
My friend opened the instrument in order to clean it and when he used the counter again to detect radiation, to his surprise, he heard multiple frequent clicks, meaning that the portable device was next to “something” emitting either radioactive particles or rays. The tube amplifies this conduction and outputs a current pulse, which is heard as a “click” if you hear a click every now and then, you should not worry but if clicks become frequent it means you are near a radioactive source). He neared the counter to the glass of the instrument and got no audible tone ( the Geiger counter has a gas-filled tube that conducts electricity when a particle or photon of radiation makes the gas conductive. His Geiger counter is able to detect alpha and bravo particles, and gamma rays. This friend has also a small Geiger counter that he uses to inspect all the items he receives from abroad because he was taught nuclear physics at school. Here’s the reason why.Ī friend of mine, who’s keen on aviation, recently bought on eBay an old ADI (Attitude Indicator). However, former pilots and current airliners crew and frequent flyers could find something interesting in this article. If the glass spheres are ground down by accident the Tritium gas would just fly away presenting no hazard.This post is addressed to the many visitors of this site who repair, restore or simply collect old instruments like altimeters, turn and slip indicator, compasses, etc. The radioactivity emitted by Tritium is low energy (penetrating power) and so it does not pass through the glass. In Tritium fluorescent watches (marked with a T on the dial) the radioactivity is from the Tritium gas that is contained together with the fluorescent material in glass micro-spheres.
This short-lived glow is phosphorescence caused by light, whereas the radium induced glow is usually called fluorescence. If a thin layer of paint such as Luminova is applied over the old dial numbers or hands then it will glow because of the radium underneath, and this glow will be permanent lasting longer than the short-lived glow from exposure to light or ultra-violet rays (sunshine). The radium is still active but not the fluorescent material that was destroyed long ago by the radiation. The only radioactivity in everything that has been mentioned in this post is the very old residual radium paint on the dial and hands of vintage watches. This is a point I still do not grasp: are all luming pastes, even the new ones, radioactive? Are the ones Ranfft sells radioactive? The above dial has a radiation dose rate above the crystal of 40 micro Sv/h. If you do want to get into this game then buy a cheap (post Fukushima) radiation monitor from one of the Japanese eBay sources. Activated ZnS is available in small quantities from: Silver activated ZnS paste would also perform well and be nearer to the original. Then it could be brought to life again to glow all night long by the application of a layer of Luminova paste over the old numbers and hands. Our conclusion is that if you have a radio-luminescent dial in good condition such as this one
He also reported that Luminova was also activated in the same way but with more brightness than the ZnS. I asked Ranfft to test this out and he found that non-activated ZnS applied over an old radio-luminous dial did glow even after several hours in the dark when the light-activated phosphorescence would have vanished. But a dial with a good coating of old luminous paint (see below) can be brought to life again by applying a new overlay of ZnS.
Today an early Radium dial has no more radio-luminescence due to radiation damage to the phosphor (usually silver activated ZnS). The early Radium luminous dials and hands glowed continuously due to the very long lifetime Alpha and Beta emission. These will glow for a few hours after exposure to sunlight (phosphorescence). One is based on the phosphor Zinc Sulphide (ZnS), the other on Luminova. Roland Ranfft is offering two re-luming pastes with excellent instructions on their use (as in Mark's video).
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