From Stone Age to High Tech - Wacker Chemie AG

From Stone Age to High Tech

Danger from Microorganisms

Before the Lascaux cave was discovered in the 1940s, it had not been exposed to humans for a long time. Such self-contained biotopes are often a paradise for specially adapted microorganisms, which form a sophisticated ecosystem that leaves the paintings undamaged. If conditions change, different microorganisms that can damage the art works reproduce.

As early as 1960 – only twelve years after the cultural monument had been opened to visitors – green algae could be seen on the walls. The delicate equilibrium previously maintained by the system became unbalanced. Only three years later, the conservators saw themselves forced to start combating the green biofilm growing there. They used a number of agents for this, including various antibiotics and chemicals.

At the turn of the millennium, another threat emerged, this time not green but white. Fusarium fungi colonized the cave, covering the walls with a white fuzz. Since, 2006, black patches have also been weaving their way from ceiling to floor. To combat all these fungi, the conservators again resorted to a cocktail of antibiotics and chemicals, together with elaborate physical cleaning and improved ventilation. Another partial victory in the battle to preserve the 17,000-year-old Lascaux Stone Age masterpieces for future generations.

In 1983, the first visitors walked through the facsimile caverns of Lascaux 2, containing some 90 percent of the wall paintings. This mecca for Stone Age enthusiasts has since been viewed by ten million people. ’Such a stream of visitors is bound to cause damage, so, after the three decades that Lascaux 2 had been open, we were involved in the urgent repair work,” explains Francis Ringenbach, artistic director and head of production at the Atelier des Fac-Similés du Perigord – AFSP. The company developed a process for scanning a cave in three dimensions and using the data to produce a millimeter-accurate reproduction from an artificial stone. The choice of silicone for moldmaking was the result of close technical cooperation between Group Gazechim (a WACKER partner in France) and AFSP.

The silicone elastomer is applied to the polystyrene model to produce a negative mold.

For both Lascaux 3, a mobile exhibition on show across the world since 2012, and now Lascaux 4, the AFSP experts have reproduced the cave complex in panels corresponding to the original Lascaux 1. They invoke in visitors the same feelings that stirred the four teenagers, when, on September 12, 1940, they became the first people in thousands of years to walk through the halls of Lascaux and see with their own eyes the unique character of this Stone Age monument.

The Lascaux cave complex is located in South-Western France, 150 kilometers north of Toulouse. Stone Age hunters probably sheltered here during the last Ice Age, the Würm glaciation.

In the process developed by AFSP, the scientists map out the original Lascaux 1 cave with great precision using a 3D scanner, and take photos of all the walls. This data enables them to make accurate copies of the wall contours using 50 polystyrene panels, into which the shapes taken from the 3D scans are cut. On average, they correspond to about 20 square meters of the original wall surface. The conservators apply a molding compound to the foam polystyrene panels by hand to complete a faithful copy of the original: the master mold. They also manually transfer the colored reference points of the wall paintings

From the 3D Scan to the Replica

The deceptively realistic imitation of the Lascaux cave is the result of state-of-the-art computer technology, years of experience with the materials, and a sensitive artistic touch.

  1. Preparing a Master Mold
    Foam polystyrene blocks are cut to size based on the 3D scan. The technicians smooth over unevenness with a mineral coat. They mark the outlines of the paintings with reference points.
  2. Copying the Master Mold
    A layer of ELASTOSIL® M silicone (yellow) is transferred to the master, copying all the details. It is part of the negative mold.
  3. Preparing the Negative Mold
    The negative mold is stabilized with casting resin and a metal scaffold. Then the polystyrene master mold is removed.
  4. The ReplicaIs Created
    The specialists transfer the veil of stone onto the negative mold.
  5. The Negative Mold Is No Longer Needed
    It is supported by another casting resin coat, while stability is provided by a metal scaffold. The stabilizing casting resin coat and the silicone of the negative mold are removed.
  6. Finalizing the Panels
    After the ELASTOSIL® M coat has been removed, experts apply patina to the imitation stone that remains. Finally, they add the original wall paintings using the reference points duplicated in the silicone as a guideline.