LED spotlights illuminate stalactite cave
The key to an extraordinary and sustainable nature experience: LED spotlights from dot-spot illuminate the Devil's Cave Pottenstein
Created by nature over thousands of years in absolute darkness, only light makes true beauty and monumental splendour visible. The rich stalactite ornamentation of the Devil's Cave in Pottenstein in Upper Franconia, the largest of the approximately 1,000 caves in Franconian Switzerland and one of the most beautiful show caves in Germany, has been restaged for visitors from all over the world using lighting technology.
They were getting on in years - the lights that used to amaze thousands of visitors to the stately stalactites and stalagmites on 1.5 kilometres of circular path through the cave. The extreme environmental conditions in a dripstone cave challenge materials and technology to the utmost. Very high humidity of up to 98%, stalactite water containing minerals and a permanent temperature of around 10° Celsius place the highest demands on the corrosion resistance and durability of the material as well as on the luminaire concept. Thus, only LED technology, whose emitting light does not contain any UV component and does not emit any heat, preserves the cave in its original state. In the past, conventional light sources promoted an unnatural and thus undesirable growth of moss and algae in this location. In addition, the heat radiation of the luminaires in combination with the high number of visitors induced an increase in temperature of up to 3° Celsius, especially in summer. The increased temperature influenced the growth of the stalactites. Therefore, as early as 2007, luminaires with conventional light bulbs were replaced by LED luminaires. Over the years, however, these luminaires had lost luminosity. In addition, the further development of LED technology promised new lighting possibilities.
Since April of this year, the numerous halls of the Devil's Cave are now staged by 262 LED luminaires from the Franconian luminaire manufacturer dot-spot. The manufacturer of LED luminaires and lighting solutions for demanding outdoor and damp locations develops series and special luminaires for use in gardens and landscapes, in architecture and in shipbuilding. The luminaires are manufactured in the company's own factory. Out of conviction, dot-spot manufactures the housings of recessed floor spotlights and surface-mounted spotlights for permanent use in the various areas from corrosion-resistant V4A stainless steel 316L. This is an indispensable prerequisite for use in this very special environment, says dot-spot founder and managing director Thomas Hödel. V2A stainless steel would be attacked, aluminium would dissolve over time. Painted steel would also rust quickly. In this respect, the dot-spot luminaires are predestined for this extraordinary place of use.
Following the lighting concept conceived years ago by a lighting artist and in place since 2007, monochrome spots with colour temperatures of 3,000 Kelvin, 4,000 Kelvin, red and blue, as well as spotlights with RGB and RGB+white colour change are used today. The lighting concept is optimised by the type and number as well as the positioning of different surface-mounted spotlights from the Franconian luminaire manufacturer. The clarios flex beam surface-mounted LED spotlight from dot-spot offers particular variability: by turning the front luminaire unit, the beam angle of the spotlight can be variably adjusted from 10° to 45° while still on site. In this unusual environment, the interplay of light and shadow can thus be adjusted during installation and even changed at a later date.
For illumination of small niches and for even more focused accents, the miniaturised clarios-mini LED object spotlight complements the luminaire portfolio used. With a beam angle of only 6°, the small spotlight professionally sets the stage for the column-shaped stalagmites and stalactites, clearly outlined and light-technically delimited from the illuminated surroundings.
The individual luminaires and the sequence of scenarios are controlled via a DMX signal. To fully exploit the potential of the new luminaires, Horncolor Multimedia from Puchheim reprogrammed the scenarios and created new, impressive worlds based on the existing concept.
The DMX control units together with the control gear required to operate the low-voltage luminaires find space and special protection in a box, the so-called Multibox from dot-spot. The special feature of this box: The Multibox does not let any moisture into the box due to the integrated membrane, but it releases possible condensate into the environment. Thus, the operating and control devices are optimally protected for permanent use.
The passages of the cave that follow the enormous 25-metre-wide and 14-metre-high portal, the "gateway to the underworld", are illuminated by LED high-voltage spotlights, also developed and manufactured by dot-spot. The luminaires of the clarios eco230 series are connected directly to the 230V mains supply. An operating device required for the low-voltage spotlights, which cannot be accommodated in these areas, is not necessary.
However, karst caves such as the Teufelshöhle in Pottenstein do not only place extreme demands on the material. The installation is also an absolute challenge. In Pottenstein, this was professionally mastered by R & S Held Elektro from Betzenstein. The ground is not level at any point. The stalagmites and stalactites, which grow only about 1 centimetre in 100 years, must not be damaged either by the installation of the luminaires or by the laying of the cables or by the movement of the installers themselves. One improper installation of the lights in an awkward location, one carelessly discarded tool or one wrong move and something could be destroyed that took millennia to come into being.
Since April 2019, the Devil's Cave in Pottenstein has been shining in new light again. With around 140,000 visitors per year, the cave is one of the most visited show caves in Europe.
Project stakeholders
Operator: Zweckverband Teufelshöhle, Pottenstein
Luminaire manufacturer: dot-spot GmbH & Co KG, Schwarzenbruck
Electrical installation: R & S Held Elektro GmbH, Betzenstein
Programming: HORNCOLOR Multimedia GmbH, Puchheim