The Nymphenbad in the Zwinger is being renovated

Use of the fountain has left visible marks

According to the SIB, years of use have left visible marks on the historic structure. The constant flow of water—from May to October each year—has worn down the soft sandstone, while organic deposits such as lichens, mosses, and algae have eroded the surface structure. “In addition, the leaching of lime from the joint mortar has led to stubborn deposits on the sculptures and walls.”

Sandstone must be desalinated

Various artisanal methods are being used to repair the damage. For example, the problematic layers of lime are removed and dissolved using formic acid, while organic deposits are removed using steam. Another aspect is the desalination of the stone: using compresses made of cellulose and clay, which are soaked in demineralized water, the salts are drawn out of the stone.