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Luminous tubes for watch faces
Beginner's Guide

Luminous tubes for watch faces

Tuesday, 13 November 2018
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Timm Delfs
Freelance journalist

“Unlike a watch, a sundial never stops.”

A freelance journalist working from Basel, Timm Delfs is also the owner of Zeitzentrale, where he sells all sorts of timekeeping instruments including his particular favourites: sundials.

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3 min read

The enormous advantage of the luminous elements developed by MB-Microtech lies in their continuous luminosity that does not need any activation, whereas SuperLuminova-coated watch hands only remain luminous for several hours after having been exposed to light.

Last October CEO Roger Siegenthaler inaugurated the newly built manufacturing building of the enterprise MB-Microtec in Niederwangen on the outskirts of Bern. Indirectly the event was also a celebration of the 100th anniversary of the enterprise that was founded in 1918 by the chemists Walter Merz and Albert Benteli. Their company started by developing special glues to bond luminous substances like radium and later tritium to dials and hands for watches and compasses. Their products were also widely used by the aviation for on-board instruments and by the weapon industry for aiming gauges. The well-known glue trademarked Cementit, which is still in production today, was a by-product because the amounts of glue needed for luminous substances was very small, and the best thing to do with the excess volume of glue was to fill it into tubes and sell it separately.

Seconds hands are being equipped with Trigalight at MB-Microtec
Seconds hands are being equipped with Trigalight at MB-Microtec

In 1968 Merz + Benteli was split into two independent entities, Merz + Benteli and MB-Microtec. While the former went on specialising in glues for universal purposes, the latter continued developing luminous elements. Radium had long been abandoned in favour of tritium due to the former’s high radioactivity and the inherent danger for collaborators and clients. Tritium is an element that is much less radioactive and was widely used in watchmaking before the advent of the inert Luminova in 1998, invented and marketed by the Japanese company Nemoto & Company.

Trademarked “Trigalight”

MB-Microtec succeded in staying faithful to tritium because they had long before developed another way of making use of its qualities while at the same time avoiding the dangers in production and application. The solution lies in the use of glass tubes coated with zinc sulfide on their insides and filled with gaseous tritium. Once filled, the tubes are hermetically closed at both ends by melting the glass with the aid of a laser. The trapped gas reacts with the zinc sulfide coating making it emit light constantly during at least 20 years, a process often referred to as GTLS (Gaseous Tritium Light Source). The radioactive decay of the tritium gas makes the tritium atoms emit electrons that hit the zinc sulfide coating and make it emit photons. But don’t worry about the radiation: it is as faint as the radiation of a fruit like a banana.

This is how the Traser P68 Pathfinder Automatic Blue presents itself during the first few hours at night
This is how the Traser P68 Pathfinder Automatic Blue presents itself during the first few hours at night

MB-Microtec produces these luminous glass tubes in different colours and diameters ranging from 0.3 mm to 5 mm. Free forms like balls and lens shapes are also possible. The thinnest tubes are so lightweight that they can be used for the hands and dials and watches. MB-Microtec delivers them to 50 different watch brands, the best-known ones being Luminox, a member of the Mondaine Group, MB-Microtec’s own watch brand Traser and Ball Watch. The miniature glass tubes are fixed in recesses in the hands and faces of these watches. The enormous advantage of these luminous elements that are trademarked “Trigalight” lies in their continuous luminosity that does not need any activation, whereas SuperLuminova-coated watch hands only remain luminous for several hours after having been exposed to light. After that period of time their luminosity drops below visibility. Trigalight-equipped watches are therefore ideal for the use in environments without much light like caves and wherever light sources should be avoided like in military operations. It is therefore not surprising that the first people who incited MB-Microtec in 1989 to start producing watches were members of the US Army. One of them, Barry Cohen, is also the founder of the watch brand Luminox.

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