SAVOIR FAIRE What allows me to read the time in the dark?

Reading the time in the dark with ease has been a priority for the brand since 1978, when ‘Heuer’ as it was named at the time produced its first series of dive watches. Luminescence for perfect legibility was one of the six features that imperatively defined their sports watches, in addition to a unidirectional rotating bezel, a screw-down crown, water resistance to at least 200 meters, a sapphire crystal, and a double safety clasp. These qualities remain true until today.

These elements of comfort and security that Super-LumiNova® brings to our lives today are now taken for granted. But it has not always been this easy, and prior to the discovery of luminescent materials, a long process of innovations over the centuries, first by sound and even by touch, attests to our desire and need to know the time in the dark.

Striking clocks that regulated village life in the 12th and 13th centuries continued to strike throughout the night. By the mid-18th century, sophisticated acoustic complications with small hammers and gongs chimed the hour on the hour automatically and later, when activated via a push piece, the number of hours and quarter-hours, and minutes. The first wristwatch example was made in 1892, while, parallel to these striking timepieces, the “tact” watch, invented In 1799 by Abraham-Louis Breguet, allowed the wearer to “feel” the time with their fingers, day and night. 

This all changed with the discovery of radium in 1898 by Marie and Pierre Curie. A radium-based paint developed ten years later was applied to dials and hands through to the 1960s, with eventual reduced quantities of radium and protection and safety controls. This material can still be found on vintage watches that date from the 1910s to the 1960s. From the early 1960s through to the early 2000s, paints containing tritium or promethium were used as low-level alternatives to radium. Tritium dials usually show a small “T” at 6 o’clock, and all are safe to wear as long as they remain closed and intact. 

In 1941, a certain Mr. Nemoto in Japan developed a luminous paint using non-radioactive photoluminescent pigments, officially patented as LumiNova in 1993, acquired that same year by Swiss-based RC Tritec AG that until today produces and distributes LumiNova under the registered name of Super-LumiNova®.

Super-LumiNova® has been used by TAG Heuer since 1998. It’s a strontium aluminate-based non-radioactive and nontoxic photoluminescence of pigments. Painted on dials, hands and indexes, Lumi-Nova photons are charged by light, natural or artificial, absorbing light energy and re-emitting it in the darkness, creating a phosphorescent glow. Brightness decreases as the energy level slows down, with the production of glow depending upon the length of time the protons have been exposed to light. Pigments are available in a variety of colours, and there are also different grades of Super-LumiNova®; these, in addition to the number of layers applied, determine the brightness of the glow.

The TAG Heuer Aquaracer series, starting with its Professional 300 model for diving, illustrates an artful use of Super-LumiNova®. With its green indexes and hour hand, distinct from the diving information indicated by the blue glow of the triangle marker on the bezel, the minutes hand for essential and precise counting, and the tip of the seconds hand to let us know the watch is in perfect running order. 

Similarly, the TAG Heuer Aquaracer Professional 200 Solargraph features the same green Super-LumiNova® on indexes and hour hand with blue glow on the minutes and entire seconds hand. Two perfect pieces for an easy reading of time during all your outdoor activities and adventures.