Watches that glow in the dark are not only practical, they used to be e.g. a vital aid for divers. Even today, luminous hands and indices are still essential features of diving watches like the Circula AquaSport. In contrast to the radioactive and permanently luminous substances that were still used until a few years ago, nowadays Super-Luminova is mostly used to light up the hands, numerals or indices of a clock.

What is Super-Luminova?

Super-Luminova are luminescent pigments (not noctilucent pigments!) Based on alkaline earth aluminate, which work in a similar way to small light storage batteries. If Super-Luminova is mentioned, then it is mostly Swiss Super-LumiNova® from the Swiss company RC TRITEC AG, which is 100% made in Switzerland and mainly used by the Swiss watch industry.

So that the pigments can be applied to watches, they have to be mixed with lacquer as a carrier layer. They can then be applied to the pointers, indices and bezel using an allocation pen, the so-called stylograph, screen printing or transfer / pad printing.

Characteristics of Super-Luminova

In contrast to its predecessors Radium and Tritium, Super Luninova is not radioactive. It is also REACH-compatible (i.e. harmless to health), temperature-resistant and insensitive to environmental influences – provided it has been applied correctly.

Durability of Super-Luminova

The luminous pigments can be charged with both daylight and artificial light (e.g. from a flashlight) and then continuously emit the stored light energy, i.e. the afterglow becomes weaker and weaker until the watch is charged again with daylight or artificial light. The charging process itself can be repeated indefinitely, as Super-Luminova does not wear out and does not lose its luminosity over the years.

In order to get a good result when applying the luminescent pigments, various things must be considered, such as the correct mixing ratio of paint and pigments, the ambient temperature, the thickness of the application, the type of drying (bake or in the air), the application of a second layer or how the hands, indices or numerals were cleaned before the luminous material was applied.

Super-Luminova lighting duration

Depending on how intensely the luminous pigments are charged, they can glow for a few minutes or all night. If the luminous markings have been applied in sufficient size and mass, perfect readability is guaranteed throughout the night in accordance with ISO 3157. Incidentally, how thick the luminous material was applied has no influence on the duration of the light – it is a purely optical design element, since numbers and indices appear more three-dimensional when applied in multiple layers.

Super-Luminova Grade

The different quality grades relate to the afterglow power and the duration of the light. Super-Luminova is available in three different qualities:

  • Standard Grade
  • Grade A
  • Grade X1

The Standard Grade has the shortest burn time and X1 the longest.

Grade X1 is easier to activate and after two hours it glows 60% brighter than Grade A.

The most common Super Luminova color variants

Relative Brightness Yield of Super-LumiNova Colours

Super-Luminova C3

C3 is yellowish in daylight and glows green in the dark. With a relative luminosity of 100%, C3 is the brightest Super Luminova.

Super-Luminova BG W9

BG W9 is white in daylight and glows green-blue in the dark. The name BGW is made up of the English color names: blue green white. Compared to C3, BG W9 has a luminosity of 95%.

Super-Luminova C1

C1 is white in daylight and glows green in the dark. With a luminosity of 31% compared to C3, C1 is very subtle.

Super-Luminova Old Radium

Old radium is light orange to brownish in daylight and glows green in the dark.

Despite the wide range of colors (blue, green, violet, white, yellow, orange, pink …), Super-Luminova in green and blue tones are mostly used for watches. The reason for this is that the human eye can best recognize green afterglow when one comes from daylight into a dark room. Once the eye has got used to the darkness, blue afterglow is easier to see.

For the Circula AquaSport we therefore use Swiss Super-Luminova C3 for the hands and indices, as well as BG W9 for the markings on the bezel.

Super-Luminova BG W9 und C3

The predecessors of Super-Luminova

In the past, from the beginning of the 20th century to the 1960s, radioactive substances based on radium were used to make wristwatches glow. These then radiated continuously and without having to be charged, but the coating had (and still has today, due to the long half-life of 1622 years!) unhealthily high levels of radioactive radiation.

At the end of the 50s, weakly radioactive isotopes such as tritium and promethium were used instead of radium, which have a half-life of only 12.5 years and whose rays cannot penetrate the metal cases and glasses of watches.

In 1973 the Japanese company Nemoto & Co. finally developed a long-lasting phosphorescent pigment based on radioactively activated zinc sulfides.

It was not until 1993 that Nemoto & Co. succeeded in developing the phosphorescent and completely non-radioactive pigment LumiNova®. In contrast to the phosphorescent pigments based on zinc sulfide, these pigments were ten times lighter and also glowed ten times longer. Within a few years, LumiNova replaced luminous paints that used radioactive materials.

In 1998 Nemoto joined forces with the Swiss company RC-Tritec in order to manufacture high-quality afterglow pigments, namely Swiss Super-LumiNova®, for the Swiss watch industry.