The Secret of the Most Readable Dials
Approaches to making dials more readable are many and varied; they can be mechanical, technical, optical, or aesthetic. Here’s an overview of the clever ways watchmakers enhance the beauty of time.
When you see certain pieces succumb to the allure of full black, you can’t help wondering what the watch designers were thinking. Black cases, black dials, black hour markers, and black hands are ideal – if you don’t want to actually see anything. If you do, you’re likely to plunge into dark despair.
Fortunately, readability is (almost) always a concern for watchmakers. Just prior to the advent of the wristwatch, this was illustrated by the introduction of radium to dials, under a patent filed in 1903 by mineralogist George Frederick Kunz – also one of the founders of the carat measurement for precious stones.
Goodbye Radium, Hello Tritium
Although radium was enduringly radioactive, it nevertheless held sway for half a century, into the 1960s. It was abandoned at a very late stage, the impact of the notorious Radium Girls lawsuit in 1927 notwithstanding; it was eventually replaced by tritium, the new symbol of night-time readability for watches – by now being worn on the wrist. Tritium has fewer harmful effects on health, but is also less durable, and requires authorisation in certain countries, making its use in encapsulated form more complicated for brands such as Traser.
Ball Watch is the main brand to use encapsulated tritium hour markers on its watches, thus making the time more legible. The implementation is by MB Microtec, whose gas micro-tubes do not require a battery or exposure to any source of light. However, the light intensity of the gas micro-tubes can deteriorate with the passing years. Tritium is present in the highly stable form of a pure gas, sealed into a mineral glass body. The inner walls of the glass are coated with a luminous material that emits a cold light when excited by the electrons given off by the tritium.
Even though it produces an interesting source of permanent light, the principle is quite complex to implement, requires the hour markers to be quite high, and runs up against certain customs difficulties. For all these reasons, Swiss watchmaking brands scarcely use tritium at all these days; almost all of them prefer the renowned Super-LumiNova, SLN to its friends.
SLN – The True Story
Nemoto, a Japanese company, was the first to develop this non-radioactive substitute, still dogged by a number of popular misconceptions. The first of these is that Super-LumiNova is a better version of LumiNova. That’s mistaken: the two products are quite different, with different compositions and therefore different uses. LumiNova is a bulk industrial substance, used for road signs amongst other things, while Super-LumiNova is used only in watchmaking.
Another oft-repeated assertion is that Super-LumiNova has always been that familiar blue-green colour. That too, is wrong, and for two reasons. While the night-time pigment can be blue or green, in some rare cases it can also be red. This third colour requires more developments and a highly stable physical environment, so it is rarely used in watchmaking. However, in the family of day-time pigments, you can have any colour you like. Combining the best of both worlds can result in hour markers of any hue by day that glow green or blue – or, in the best instance, blue-green – by night.
The third preconceived idea is that Super-LumiNova is a generic and widely-used product. Yes… and no. The 1994 patent covered the design of the material for a period of 20 years; this has now lapsed. However, the joint venture between Nemoto and its partner Tritec anticipated this, and filed other patents in the meantime. As a result, it is now virtually impossible to reproduce Super-LumiNova without infringing these new patents. That said, Billight is one third-party company that has garnered fame for adding a luminous touch to certain timepieces by IWC, Speake-Marin (the Spirit), Chanel (the J12), Zenith (the Pilot) and F.P. Journe (L’Elégante).
Black & White
These tricks of the light are not always enough to provide perfect readability: the mechanics and design of the watch are determining factors, too. There can be no doubt that black and white contrast is ideal. The Rolex Daytona offers proof of this, as are all the so-called ‘panda’ and ‘reverse panda’ dials. The latest Monaco by TAG Heuer takes a leaf from a very similar book with its light grey background.
When it comes to hands, watchmakers don’t hesitate to use their own individual techniques to improve readability. For instance, Grand Seiko is renowned for the Zaratsu finish of its profiles and curves, making them perfectly clear, as on its very recent SLGH005.
More Room, More Readable
From a mechanical point of view, the invention of the large date provides a dedicated disc for tens and another for units on the date display. Each figure thus has more room, making it more readable. A. Lange & Söhne is one of the masters of this practice, as evidenced by its historic Lange 1. The manufacture has extended its knowhow to decimal time, too, as on its Zeitwerk. More generally, window displays provide remarkable performance in terms of readability, as can be seen on Patek Philippe’s most recent Perpetual Calendar 5236P-001, featuring a fine example of an in-line display.
Another trick used to improve readability is the magnifying glass. The first example that springs to mind is the unmissable Cyclops by Rolex, in particular on its Explorer II, but other firms have extended the principle as well. MB&F’s HM3 takes quite a fun approach, using large crystal hemispheres to display its highly luminous hours and minutes.
The Genius of the Independents
Urwerk takes a more technical and more unexpected tack, having found a most unusual way of making the seconds more readable on its UR-111C. The seconds units are arranged on two wheels: 10, 20, 30, 40, 50, and 60 on one side and 5, 15, 25, 35, 45 and 55 on the other. The assembly involves a fibre-optic cluster located one-tenth of a millimetre above the indication. Unlike a magnifying glass, the fibre optics don’t distort the image – they project the seconds onto the frame, so that reading them is simplicity itself.
The same principle of non-distortion has been enlisted for Ressence’s Type 3 and Type 5, with a time module located in an oil bath that cancels out any distortion caused by light or the curvature of the sapphire crystal.