Following their discovery in 1856, the frescoes significantly faded. The paintings depicting the life of
Christ were to be preserved in an authentic state and not restored, reflecting their historic and artistic value. The
Swiss technique of
Bildtapeten, or picture wallpaper, was introduced to the church as a way to display a clean mural without restoring the original work. Depending on the visitors, the
Bildtapeten could be raised and lowered from a mechanism installed in the ceiling. For example, the
Bildtapeten might be lowered for mass to provide a complete picture of the paintings, then raised to reveal the original frescoes when art historians or other experts are inspecting the walls. Academic painter Carl Schilling began creating and installing the
Bildtapeten in 1889 and completed the project in 1891. In 1909, the
Bildtapeten was removed after a part of the mechanism broke. A
restoration that included partial repainting and artificial patination was completed by Victor Mezger between 1921 and 1922. A subsequent rise in visitors damaged the frescoes, requiring the church to closely monitor their state. This increase has led to climate change within the church building. As more bodies enter the church each year, the
humidity and
pollution levels in the building increase. This humidity and pollution created an environment ideal for the growth of
mold and
bacteria, further damaging the frescoes. The frescoes are monitored by
Landesamt für Denkmalpflege and the
University of Stuttgart, Institute for Materials of Architecture. These groups collect data on
indoor climate,
microclimate impacts,
air motion,
radiation, and visitation. These data were expected help prompt new methods by which to regulate the indoor climate, including visitor access. ==See also==