Watch Luminous

A luminous watch is the one where hands, indicators glow in the dark. It makes telling the time super easy, even when there is no light around. In watch industry, Lume is shorthand for luminescence substances glowing solution that is applied to watches to achieve ‘glow-in-the-dark’ effect.

Prior to 20th century, there was no practical solution for reading the time in darkness on watches. In the early 20th century, with the development of luminous substances, watchmakers successfully applied this new technology to watches. 

Luminous watches became a crucial tool in World War I, enabling soldiers on the battlefield to tell time in the dark.

Nowadays, watches with luminous are still popular because of their practicality and aesthetic appeal, particularly their ability to be easily read in low-light conditions. The luminous material on the dial, hands, and markers allows users to quickly tell the time in the dark. This functionality is particularly useful for professionals like pilots, divers, and military personnel, as well as for everyday activities like checking the time during a movie or while camping. Besides, luminous details add a visually interesting element to a watch's design, enhancing its overall appeal and making it a desirable feature for watch enthusiasts. 

Over 100+ years, luminescence substances in watch industry have evolved from the use of radium in the early 1900’s to today’s various luminescence materials such as Super-LumiNova, Chromalight, LumiBright etc. 

LumiNova was invented in 1993 by the Japanese firm Nemoto & Co., and quickly became the gold standard for watch luminescence. After that, Nemoto & Co. established a join-venture with RC Tritec AG called LumiNova AG, Switzerland to manufacture 100 percent Swiss made afterglow pigments branded as Super-LumiNova. 

Super-LumiNova is a brand name for non-radioxic, non-toxic strontium aluminate-based photoluminescent pigments. Super-LumiNova’s core technology utilizes europium/dysprosium-doped strontium aluminate (SrAl₂O₄:Eu²⁺, Dy³⁺), patented and trademarked as Luminova® by Nemoto & Co., Ltd. in 1994. Nemoto began licensing this technology to watch brands in 1998,with Super-LumiNova being one licensee. This technology (SrAl₂O₄:Eu²⁺,Dy³⁺) formulation delivers significantly brighter and longer-lasting luminescence than traditional zinc sulfide pigments — being approximately 10 times brighter, lasting 10 times longer, and costing 10 times more, accounting for Super-LumiNova’s premium pricing.

The luminous color of Super-LumiNova is determined by the luminescent properties of its phosphor (strontium aluminate doped with europium/dysprosium) and added fluorescent dyes. The default color after Super-LumiNova baking is green (C3). All other observed luminous colors are achieved through fluorescent dyes, which alter the excitation/emission spectrum and limit the amount of light absorbed and released by the phosphor. Consequently, all colors except C3 exhibit reduced lumen performance compared to C3. This is why C3 is indeed the brightest.

Super-LumiNova, when properly applied and charged, will glow brightly for a few hours and remain visible in the dark for up to 10 hours. It does not degrade or age over time and will continue to glow for the lifetime of the watch as long as it's charged. The intensity of the glow will decrease over time, but it will still be visible in low-light conditions for a significant period. 

Super-LumiNova offers three grades: Standard, Grade A, and Grade X1. Not all color variants are available in all three grades. While initial brightness shows no significant difference between grades, Grade A and Grade X1 exhibit significantly slower light intensity decay over time, meaning Grade X1 remains visible the longest.Super-LumiNova technology introduced Grade X2 to enhance readability in low-light conditions.

RC Tritec AG recommends a maximum coating thickness of 0.30 mm for Super-LumiNova pigments,as exceeding this limit prevents ultraviolet light from penetrating effectively to reach and activate the underlying pigment layers.

Rolex introduced its proprietary Chromalight luminescent technology in 2008 with the Deepsea watch, applied to hands, hour markers, and the luminous dot on the rotating bezel. Its composition is an aluminum-strontium-dysprosium-europium complex developed in-house by Rolex through sophisticated processes to ensure exceptional performance. Chromalight emits a distinctive blue glow, with brightness and longevity significantly surpassing traditional phosphorescent materials: Luminescence duration is nearly doubled, intensity remains stable over time, and brightness is exceptionally uniform and vivid. It exceeds horological industry standards in persistence and consistency. This design is engineered specifically for deep-sea dive watches, ensuring legibility in extreme darkness.

LumiBrite is Seiko’s recent development in Seiko luminous paints, delivering substantial improvements over conventional products. It offers four core advantages: significantly longer afterglow, glowing for 3–5 hours in darkness (>10× longer than traditional luminous paints); higher brightness surpassing both conventional phosphorescent and radioactive materials; a non-radioactive composition ensuring safety and eco-friendly; and an extended lifespan that maintains quality long-term, enabling semi-permanent use.

Phosphorescent materials were discovered in the 1700s, with centuries of research and refinement.

1866: Zinc sulfide (ZnS) was reported, requiring activators (e.g., Cu, Ag, Mn) and complex purification to produce phosphorescence under blue/UV light.

1898: The Curies discovered radium. Radium decay releases ionizing radiation that excites fluorescent chemicals (e.g., ZnS), causing radioluminescence. However, radium is highly radioactive and toxic.

1953: Gaseous tritium light sources (GTLS) emerged. Tritium undergoes β-decay, releasing electrons that phosphoresce the coating. These offered weak light output and carried leakage/radioactivity risks.

1993: Employees of Nemoto & Co., Ltd. developed strontium aluminate pigment and patented in 1994. its commercial trademark became Luminova®.

1998:Nemoto & Co., Ltd. licensed strontium aluminate technology to other manufacturers/watch brands (e.g., Super-LumiNova and Seiko’s LumiBrite).

Luminescence refers to phosphorescent pigment which repeatedly absorbs light (usually daylight or UV light), stores the energy, and then slowly glows in the dark for minutes to hours or longer.

Luminescence technology has transitioned from hazardous to safe. Today, strontium aluminate (Luminova®/SrAl₂O₄:Eu²⁺,Dy³⁺) is the brightest, longest-lasting, non-radioxic phosphorescent material commercially available.

Today, there are many well-established luminous brands and a wide variety of colors available. Super-LumiNova stands out as the industry leader and is the top choice for many major watch brands. However, Seiko LumiBrite and Rolex Chromalight are proprietary—they are not sold to external watch manufacturers. Additionally, there are many other luminous brands from Japan and China.

So, how should watch brands select the right luminous material when designing and producing their watches?

If it’s a professional dive watch, high-performance lume is essential. We strongly recommend Super-LumiNova or premium Japanese alternatives. If the watch is not a dive model and lume is only needed for occasional low-light readability or decorative purposes, Japanese or Chinese luminous brands may suffice.

For watches with a factory price (wholesale price) above $50, Super-LumiNova is worth the investment. However, for budget-friendly watches (factory prices under $20), it’s more cost-effective to use Japanese or Chinese lume brands and allocate funds to other components. For example, a Rolex Submariner dial with Super-LumiNova C3 may cost 3-5 times more than the same dial using alternative luminous materials.

A single watch often has multiple luminous parts—dial indices, hands, and bezel markers—and their glow must match in color and brightness. This requires:

However, achieving this is challenging for most of watch factories because their watch components are typically sourced from different suppliers. Even if the same Lume brand is used, variations in application techniques and mixture ratios can lead to inconsistencies.