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Good evening, everyone!
This column discusses mechanical watches from an engineer's perspective. For our 45th installment, we will be discussing:
"The Evolution of Luminous Paint: Tritium, Luminova, and Chromalight"
We'll be exploring this topic.
When choosing a luxury watch, "luminous paint" plays a very important role.
The indices and hands glow softly in the dark. While their function as luminous paint may have been lost, some watches have undergone exquisite aging, increasing their value. Luminous paint not only offers practicality but also greatly influences the watch's overall aesthetic.
This time, we will focus on three representative types of luminous paint that have evolved over time—Tritium, Luminova, and Chromalight—and explain their differences and appeal from the perspective of a watch enthusiast.
Tritium: The "Flavor" of Vintage
First up is "Tritium," a familiar name to vintage enthusiasts.
It was a luminous paint used in many mechanical watches from the 1960s to the mid-1990s, characterized by containing radioactive material. Dials often bear markings such as "T SWISS T" or "T<25."
Characteristics of Tritium
・Self-luminous
・Luminosity weakens over time
・Some exhibit a cream to orange color change due to aging
This "aging" is Tritium's greatest charm. Uniformly darkened indices and hands are highly popular, and they alone can increase a watch's value.
However, because it contains a small amount of radioactive material, it is no longer used today due to safety standards.
*1966 Submariner 5513
*1978 Explorer "Ref.1016"
Even within the same Tritium category, the reaction to UV light and the way it ages differ depending on the era and model. These nuances are what truly captivate collectors.
Luminova: The Modern Standard in Watches
Next, we introduce "Luminova."
This non-radioactive luminous paint rapidly gained popularity from the late 1990s as a replacement for tritium. Dials typically feature "SWISS" or "SWISS MADE" markings, and the "T" indicating tritium is absent, with some exceptions.
Even in 2025, it is still adopted by many brands, making it the "modern standard" for luminous paint. Many of you may already know that Luminova was developed by Nemoto & Co., a Japanese company. This makes us incredibly proud as Japanese!
Characteristics of Luminova
・Non-radioactive and safe
・Emits light by storing it (phosphorescent type)
・Emits a bright green light that fades over time
・Generally white to slightly greenish in color
Its practicality as a luminous material is very high, offering excellent visibility in the dark.
However, it exhibits almost no aging like tritium, and its color remains largely unchanged over time. For vintage enthusiasts, this can sometimes feel a bit lacking.
Chromalight: Rolex's Unique "Blue Lume"
Finally, we introduce "Chromalight," which Rolex began to fully adopt around 2008.
This is Rolex's unique luminous paint, and its most prominent feature is its blue emission. Compared to conventional green-glowing lume, it is said to be gentler on the eyes and easier to read in the dark for extended periods.
Characteristics of Chromalight
・Non-radioactive and phosphorescent
・Blue luminescence
・Longer luminescence duration
・Used in many current Rolex models
It was first adopted in professional models like the "Deepsea" and is now used in almost all Rolex watches, including the "Datejust." The sight of the indices and hands glowing in a cool blue in the dark truly gives the impression of a "latest Rolex."
The image above shows a watch with Chromalight indices and Luminova hands. Comparing them side-by-side clearly illustrates the difference in how they glow in the dark. Like Luminova, Chromalight also exhibits almost no aging. It is not a luminous material meant for enjoying future "patina."
Materials like Cerachrom bezels and Chromalight lume have achieved overwhelming advancements in functionality and durability. What kind of evaluation will they receive in the vintage watch market decades from now?
It's enjoyable to choose a watch while imagining such things, isn't it?
Summary
How was that?
You can see how the type of luminous paint can significantly affect a watch's popularity.
・For enjoying a vintage feel → Tritium
・For daily use and practicality → Luminova
・For the world of the latest Rolex → Chromalight
It's not about which is superior, but rather how its value changes depending on which era of watches you want to enjoy. Please choose based on your own preferences.
We hope this article has provided valuable information and piqued your interest in luxury watches, even a little! Also, if you have any questions, please feel free to ask directly, and we will be happy to answer them thoroughly. We look forward to your visit and inquiries!
Stay tuned for the next installment! See you then!
