The sportier a watch, the more likely it is to use some form of luminescent material. Modern SuperLuminova® coatings are typically found in their most copious amounts on diver’s watches, where they help divers to read the time and the all-important dive-time bezel in the murky depths as well as at night. More all-round watches usually have more subtle applications of luminescent material, reserving it for an insert for the hands or hour markers, for example.
In keeping with its general approach to watchmaking, A. Lange & Söhne, however, does things a little differently. The brand that constructs its movements differently (using untreated nickel silver), decorates them differently (and by hand) and introduces incremental and highly practical improvements to movements (see below) naturally had to find a different way to add luminescence to its timepieces. Thus the “lumen” phenomenon was born, in 2013, with the Grand Lange 1 “Lumen”, which has since been followed by a Grand Lange 1 Moonphase, a Zeitwerk and now, the fourth in the series, the Datograph Up/Down “Lumen”.
Rather than trying to emphasise individual elements on the dial, A. Lange & Söhne takes a totally different approach, aiming to bathe the entire dial in a soft green glow. To create this effect, the dial is replaced with a semi-transparent crystal that filters out most visible light except for the light from the part of the ultraviolet spectrum that is needed to charge the luminescent pigments, which are painted on the dial flange (tachymeter scale), subsidiary counters and hands (unusually, the central chronograph seconds hand is fully coated in the compound). A similar trick is used for the signature A. Lange & Söhne big date, with the digits painted in black on transparent glass discs rotating above a luminescent background. This means that the background can recharge throughout the day and does not lose any of its luminescence when the date changes at midnight.
The added benefit for A. Lange & Söhne fans is that the semi-transparent crystal offers a glimpse of the two discs for the big date function and the workings of the hand-wound L.951.7 Datograph flyback chronograph calibre. When it was first presented in 1999 this calibre set new standards for the chronograph with its flyback mechanism and patented precisely jumping minute counter, which advances by one increment every time the chronograph seconds hand passes the 60th second, even if the chronograph is stopped at that very moment.
The Datograph Up/Down “Lumen” comes as a limited edition of 200 watches in a 41mm platinum case and with a black alligator leather strap. A final detail is found on the dial and gives the watch its “Up/Down” name: a power reserve indicator at 6 o’clock with the German words “auf” and “ab” (up and down respectively) indicates how much of the 60-hour power reserve remains.
