The Engineer Hydrocarbon AeroGMT II is a classic modern Ball wristwatch: big size, bold styling, an aggressive tool-watch personality and, of course, the signature tritium gas tubes that give Ball watches their ability to maintain high visibility through prolonged periods of darkness. Most other modern watches use Super LumiNova, or a related compound, which has to be charged by ambient light, and which glows with diminishing brightness over time. Tritium, on the other hand, is a radioactive substance (much safer for use in watches than radium) that produces illumination without needing previous exposure to light; as such, it finds uses in many applications in which low light legibility is essential and where materials like Super LumiNova would not be suitable. Other modern applications for tritium gas tubes include aircraft instrumentation and gunsights, as well as numerous novelty applications, like glow-in-the-dark keychains. Before getting into the tritium vials, though, let’s look at the rest of the watch.