May 3, 2015
by David Bredan
Seeing how tritium gas tubes are made will surely remain among the coolest experiences I have had on these horology-related manufacture visits. Tritium gas tubes are these extremely tiny (about 0.5mm thick and at least 1.3mm long) glass tubes that are filled with (mildly) radioactive tritium gas – although, as we will see, there is a lot more to them than that. What these tubes do is that they are guaranteed to glow brightly and continuously for at least 10 years, without having to be charged by external light (like the luminescent material used on other watches), or needing to be activated with electricity or otherwise. These little tubes just glow, unstoppably, for up to 20 years, no matter what.
The company that is manufacturing these tubes is called MB-Microtec, situated near Bern, Switzerland. They are the only company on the market today that is capable of manufacturing these barely visible glass tubes and filling them with tritium, thanks to their special know-how for working with glass cylinders of this size. Therefore, MB-Microtec is claimed to be the sole supplier to any and all watch brands who use tritium gas tubes for their watches. As such, if you have such a watch in your collection (or plan on acquiring one), the glowing tubes you see on the hands and indices of the watch were made here, and in the way that you will see more about below. The company is also the manufacturer of its own watch brand, Traser.
Because of it being a totally independent light source, tritium gas tubes make for a reasonable alternative to lume paint. The reason for that is, as you know, “lume” needs to be charged by an external light source for it to then glow for around 10-12 hours before going completely dark once again – and remain like that until the next exposure to a strong source of light. By contrast, tritium tubes keep on glowing for years and years, all by themselves.
What you need to know is that tritium will not shine as bright as high-quality lume (like C3 Super-Luminova), but when you compare the two after around 20 minutes has passed since the charging of the lume, you can expect the tritium tubes to be noticeably brighter – and, you can rest assured, they will stay that way. So, if you enjoy the bright, vibrant glow of freshly charged lume, then tritium may not be what you are looking for – but if you want to be able to read the time early in the morning or 2 hours into a movie in the cinema, the latter is your best bet.
If you think about it, there are countless interesting ways an item with continuous and extremely reliable glow could prove to be useful. MB-Microtec was founded in 1969 (it was 1989 when the Traser brand was established), and its main profile is as a manufacturer of tritium gas tubes of all sizes is, in fact, not based on making the tritium gas tubes used for watches, but instead the manufacturing of slightly larger tubes that are used for the sights on pistols and guns. Specifically, an approximately 1-inch-long tube, most often in the color of red, is placed at the end of the barrel of the gun, while two green pieces are placed into the sight located at the other end, closer to the shooter. Therefore, when the police officer or special forces soldier goes into a dark room, he/she knows exactly where the gun is pointed, thanks to the glowing bars at the two ends of the gun. And because these pieces glow continuously, they can rely on the pieces always being visible in low-light situations, as opposed to luminescent paint that needs to be charged and fades over time.
Tritium gas tubes supplied for watches are the second greatest part of the company’s sales, followed by tritium equipped compasses and other equipment for military uses as well as “EXIT” signs for airplanes and buildings – signs that have to be legible even during a power outage and in complete darkness. The list goes on, but it is a cool thing to think about how useful a permanently illuminated accessory can be.
So, how do these tubes work exactly? The glass tubes are first internally coated with phosphor powder, then filled with tritium gas (an isotope of hydrogen gas), and last, are laser sealed, locking the gas inside. When the phosphor powder coating on the inner surface of the tube is exposed to electrons from the tritium gas, the phosphor is excited to emit light in different colors. It is this process that creates the light that we see coming from the tubes, and it is thanks to this chemical process that the tubes glow for over 20 years continuously, without requiring an external power supply, sunlight, or in fact, any maintenance.
Tritium gas is what we might call “mildly radioactive.” Its half life is 12.36 years – much, much less than the over 1600 years half life of radium, a highly radioactive material that had been used on watch dials and hands over half a century ago (you can read more about that on page 2 of our History of Dive Watches article here). While radioactivity, the way it behaves, and how it affects the human body is an extremely complicated topic, we will try and put it all into perspective.
The radioactivity of tritium is so weak that it can be stopped by a 5mm-thick plexiglass and if you were so foolish and unfortunate all at the same time that you consumed all the tritium in your watch at once, that would account for the same amount of radioactivity (40 mSv, i.e., 40 microsievert) as you are exposed to when flying from New York to Los Angeles. In other words, 40 microsievert is 1/45th of the average annual background radiation that you are exposed to each year. And so, while it certainly is not recommendable to consume the tritium from your watch indices and hands, if it were to happen, you would still be fine.
Now that we know more about tritium gas tubes and how safely they work, let’s finally see how they are made! The tubes start out as “masters,” which are thick walled, relatively shorter pieces of glass, shaped as ovals (as seen in the first picture above), or perfectly round pieces. The master cylinder pieces one-by-one go through a machine that heats them up and sends them through sets of rollers (middle picture above) which are sized in accordance with the desired final thickness of the tube. The result is what you you see directly above: a long (around 3-meters, or 10 feet) piece of glass tube that can be anything between 0.5 to several millimeters in diameter.
The pieces are then cut to around 1-foot-long pieces and are batched up to be sent over to the next department, where they receive their inner phosphor coating. Remember, this inner coating plays a key role in making the tube glow and it has to have a perfectly even inner coating to create the desired visual effect. To achieve that, first, the pieces are put into an acid (as seen directly above), which is then blown through the entire length of the tube with the use of pressurized air. This way, the inside of these tubes become “sticky,” allowing the phosphor powder to stick.
The excess acid has to burned out from the end of the tubes, which is done by hand in the way you see in the first image above. This is necessary so that the tubes can be hung and filled with gas later on. What you see above is the powder (in this instance, in green), that is poured into the tubes from above. The tubes are then bounced up and down a number of times to make sure that the powder is evenly distributed on the inside. The eight available colors are: red, orange, yellow, pink, white, green, ice blue, and blue.
Now that the cylinders have received their inner coating, they are sent over to another room where the real magic happens, as they are filled with tritium. This process is done by three large machines with a batch of about 30 tubes at a time and it takes about 20 minutes complete. The tubes are hung up from their ends which had the acid coating burned away.
What happens is that about 4/5th of the tubes are submerged into extremely cold liquid nitrogen (as you see in the shot directly above), while a worker uses a torch to heat up the container that holds the tritium. As the gas is heated up, it finds its way into the cylinders where it is cooled down extremely quickly.
The final step here involves the workers cutting the strips down individually, using a small torch which melts the glass and, as such, immediately seals the tube as well, locking the gas inside. Seeing the blowing white mist and the bubbling water underneath and around the sticks, in contrast with the blue and orange flame of the small and large torches was quite an experience. It just looked very cool, especially knowing that the result will be glowing for decades on its own, adorning watch dials, hands, or lighting up compasses and even keychains (a fantastic idea that makes finding your keys in the dark so much easier).
Once the long tubes have been filled with tritium and sealed, the pieces make it to the next station. Here, as many as 19 special machines are doing their magic, as they perform that secret operation that allows MB-Microtec to create such small tubes from the larger pieces. This is, of course, a safely guarded secret of the company, and so, while I did see how it happens, it cannot be shared – not that I could provide you the insight necessary without a proper explanation coming from the brand (which, again, was decidedly omitted at this part)… But that is just the nature of trade secrets and painstakingly developed know-how.
Once the smaller pieces are done, they are organized into plates by a machine that only picks and transfers them into these trays, but in the process, also checks each and every one through an automated process for evenness of the coating and closure. As many as over 1,300 pieces can end up in one of these trays.
Excessive care is practiced all around the manufacture with numerous radioactivity measuring devices set on the walls (as seen directly above). Different rooms have different security levels, and I am told the manufacture receives a weekly accreditation and is very closely monitored by official authorities for its processes of acquiring the tritium gas from Canada, as well as for its manufacturing processes. Also, every worker of the company is checked weekly to ensure their health.
As far as the watches themselves are concerned, timepieces often have the T≤25 designation on their dials. That means, that the watch, altogether has a radioactivity level below 1 GBq (we remember seeing Ball make some special watches with T≤100 ratings, i.e., with under 4 GBq). On an excessively nerdy note, we will add that the reason why you see GBq, i.e., giga-becquerel is because it is used here as an SI measurement of radioactivity, while the sievert we referred to further above is the SI measurement for radiation dose. (Feel free to add corrections in the comments below, as this really is beyond our comfort zone.)
The finished small pieces of tritium gas tubes are then either sold directly to brands who purchase and install them on their dials, hands, and bezels on their own, or are transferred to an assembly department where they are fitted to said components by MB-Microtec. Depending on the size of the order and the complexity of the task, either a machine is capable of picking up the pieces one by one from their container tray and then installing them to the dials, or the installation is performed by a worker at the manufacture. What you see above is how the tubes are fitted onto the hands.
First, an adhesive layer is placed onto the back of the hand, then the hand is turned upside down (so that it is the right way up) and the tube is placed into cut-out and hence on the adhesive, securing the tiny glass tube on the hand.
With that, the manufacturing process of the tritium gas tubes ends, as what is left is the assembly of the watch itself. As mentioned above, MB-Microtec’s own brand is called Traser. With prices ranging from a few hundred to a bit over $1,000, the watches are available in the tactical, sport, and elegant collections. My favorite line is that of the “tactical” timepieces, the Traser Special Force 100 that you see above comes with a titanium case and bracelet along with a NATO and a rubber strap and is priced at $650.
I must say, now that I know just how exactly these tiny, barely visible glowing gas tubes on the periphery of the dial and hands were made, I am really tempted to start saving up for a watch with some of these tirelessly shining tubes on it. traser.com