The building is altered in many places, particularly in the parts made of Vosges sandstone, the stone is made dirty and blackened throughout decades of pollution.

In 1991, the restoration of the building, listed with a preservation order on it since April 1^st 1963, is decided in close collaboration with the «Service des Monuments Historiques de Franche Comté».

The restoration starts with the façade cleaning thanks to a suction craddle fixed to the end of a pneumatic handle set on a lorry.
It is not only fast (no scaffolding) but also not traumatic (no added chemical products) for the epidermis of the stone since a very fine glass powder is thrown out under pressure by rubbing-out.
The protective deposit of the stone is preserved. After erecting a scaffolding, strong enough to support the loads, a stone-to-stone plan is laid down.
After the analysis of their sanitary condition, it allows to spot the stones to be removed.
The journeymen stone masons use 13.60m3 of the limestone from Villebois and 13.70 m3 of pink sandstone from Alsace (Schneider quarry in Bust, Bas-Rhin), grey stone from Adamswiller (Bas-Rhin, Saverne district).
If necessary after carving the stone, the journeyman gives a sheen to it (its composition remains his own secret).