For three weeks in the shadow of Mount Pilatus and snapped by thousands of Japanese, Andreas Küng has observed, recorded, photographed and mapped the 30 metre high scaffold-clad rock face. He is the project leader at the Expert Center for Monument Conservation at ETH Zurich. On behalf of the City of Lucerne, he and his colleagues have made a precise inventory and analysis of the condition of the famous sightseeing attraction. The intention is to use these to develop immediate actions and a conservation and maintenance plan.

The main problem: water

The immediate actions included breaking off pieces of rock that were in danger of falling down, and sawing off and poisoning small trees. Otherwise their roots would have broken open the rock face. Cracks were sealed with mortar to prevent them breaking open any further and a rather large slab of rock was secured with metal anchors.

Andreas Küng graduated in Geology at ETH Zurich before he started work as a historic monument conservator. While still a child he collected stones and went rock-climbing. This is why at the age of 48 he wears a climbing helmet instead of a builder’s safety helmet. His knowledge is useful to him for this historic monument because it is at the same time a geotope: “The ‘Lucerne Sandstone’ that is revealed here was deposited in the Molasse Sea 20 million years ago and solidified. The sandstone strata were tilted at an angle of 50 degrees during the formation of the Alps.”

From seashore to mountain rocks

The profile of the strata is still recognisable today. “The lion was chiselled from a particularly homogeneous, solid sandstone that was deposited close to the shoreline,” says Küng, and points to small holes and passageways on the lion’s belly. “This is where small shrimps once dug their burrows.”

During the construction of the memorial it was already clear that the dying lion is particularly in need of care. The biggest problem: water leaking through from the rocks. Repairs and restorations were carried out on many occasions. In 1893 Ludwig von Tetmajer, an ETH professor and head of the EMPA (the Swiss Federal Laboratory for Materials Testing and Research), arranged for a tunnel as high as a man, 30 metres long and with several intermediate floors, to be dug in the sandstone all round the lion’s recess. The tunnel cut off the water-bearing strata to allow the seepage water to flow away. Furrows were also cut into the rock to channel rainwater and drain it away through copper spouts.

Salt terraces in the stalactite cavern

“The first time we opened the tunnel it was like being in a stalactite cavern: the pipes had burst and cascades of water were splashing down the walls.” The ‘cave explorers’ also discovered small stalactites hanging down from the roof, while salt terraces like the famous salt terraces of Pamukkale in Turkey were forming on the floor. “The majority of the damage had occurred because the monument had not been maintained adequately.” Because one of the rainspouts had broken off, rainwater had dripped over the lion’s belly repeatedly for decades. At this point the rocky outer skin was crumbling off like baked flaky pastry.

“Whenever water runs over stone, magnesium, calcium and sulphate ions dissolve out. As soon as the water evaporates, salts such as magnesium sulphate and calcium sulphate, i.e. gypsum, crystallise and are deposited. After each downpour of rain the gypsum layer becomes thicker until the surface crust bursts open.” However the monument expert was reassuring: all that needed to be done was to seal the “open wounds” with mortar and to ensure that water no longer reached them.

Atmospheric pollution plays a negligible part. “Sulphur oxides have scarcely harmed the lion and have decreased greatly in recent years.” Even the pigeon droppings don’t worry the lion. There were several pairs of pigeons nesting in the drainage tunnel and staining the lion’s mane with grey streaks. “It’s much more an aesthetic problem,” adds Küng. “So an invisibly thin wire netting will probably be stretched in front of the recess.”

The lion is in comparatively good shape

Although the lion looks much the worse for wear and is suffering from open wounds, Küng’s conclusion is that the monument is in quite good condition: “The rock face and the lion show the usual effects of weathering, and the lion itself is in a protected position in the recess.” The front left paw, which protrudes from the recess, is the only part that is exposed to the wind and weather. This is why it has already been renewed several times. “Tetmajer’s water drainage concept has proved successful,” continues Küng. “If we repair the components again and maintain them regularly, the lion will be adequately protected.”

The Expert Center, which made this inventory and condition analysis and is now developing suggestions for maintenance and conservation, is an advisory and research institute for historic monument preservation. With its laboratories in Zurich and Lausanne, it is closely linked to both ETHs but is supervised by a foundation. The contract for co-operative work between the Expert Center and ETH Zurich initially runs until the end of the year. A decision regarding an extension has yet to be taken.