Why my Rolex Watch Glows – Rolex Luminescence Explained Part III

In Part I and Part II, we discussed the use of radioactive Radium and Tritium on dials and watch hands to provide night time visibility and utility for Rolex. Rolex, along with the rest of the watch industry, moved away from radioactive materials to much safer LumiNova and Rolex’s own Chromalight.

SWISS or SWISS MADE = SuperLuminova or Luminova

The watch and the nighttime instrument companies (eg. aircraft) faced a design constraint of producing luminescent hands and faces for analog dials that was not radioactive and harmful to workers, yet was effective in nighttime uses. The Japanese company, Nemoto, patented “LumiNova” paint back in 1941, but the paint was not accepted into the industry until 50 years later when it was obvious that utilizing radioactive materials was not an option. LumiNova paint was non-toxic, charged/activated by a wide variety of light, and has a steady glow for a long period. SuperLuminova is essentially the same material but the difference in the name is to denote it from by Nemoto’s licensed Swiss-based partner Tritec.

A LumiNova or SuperLuminova dial is distinguished by wither having “SWISS” or “SWISS MADE” at the 6:00 o’clock position in the watch dial. The difference between the use of “SWISS” between the use of Radium or LumiNova can easily be distinguished on the age of the watch. If the watch was made prior to the early 1960’s, the use of “SWISS” denotes the use of Radium. Any watch 40 years old or newer noting “SWISS” on the dial, it’s safe to think that some form of LumiNova is used. SuperLuminova is very luminescent after being directly exposed to light, then the brightness gradually softens after several hours. Depending on the time exposed to light correlates to how long the luminescence lasts. A watch exposed in the sunlight all day, will glow all night.

Although SuperLuminova is used in Rolex dials and hands, the effectiveness of SuperLuminova depends on the thickness of its applied layer on the dial or hands. The smaller DateJust dials and hands will not glow as brightly as the new Explorer II dials that have fat hands and larger hour dots.

The latest Rolex sport watches, the DeepSea, Submariner, YachtMaster IIs, and the Explorer line are all outfitted with Rolex’s Chromalight luminescence. Chromalight is exclusive to Rolex and its relationship to SuperLuminova is unknown, but the “Swiss Made” designation on the dial is still the same so it is assumed that it is a form of LumiNova. Chromalight glows with a blue hue rather than with a traditional green hue. Chromalight appears to glow brighter in ambient light better than SuperLuminova and appears to glow longer and touted to be visible for a full 8 hours, but a SuperLuminova dial will glow all night if exposed to sunlight all day.

All that being said, it appears that Chromalight is going to be another Rolex mainstay and will be another feature that separates Rolex from the rest of the watch industry.

— Featured Photo Credit: Pixabay (cc) Archive.