[M-IS05] Geomaterials in cultural heritage: weathering, investigation techniques, and conservation

[MIS05-03] Diagnostics and restoration of Lion statues made of porous limestone, a case study from Hungary

Balázs Szemrey-Kiss, Tamás Zomborácz¹, *Akos Torok¹ (1.Department of Engineering Geology and Geotecnics, Budapest University of Technology and Economics)

Keywords:limestone, diagnostics, restoration, non-distructive tests

The Chain bridge, which was opened in 1849, is a symbol of Hungary, and it connects the two sides of the river Danube in Budapest. The current study focuses on diagnostics and restoration works of lion statues on this bridge. Each of the statues has three major parts, which were mounted together. The project was initiated in 2021 when the restoration of the bridge began. In the first phase of the programme, the identification of stone types and the possible provenance analysis of the porous limestone were made. It became clear that the lion statues were made from a highly cemented good, quality of porous Miocene limestone quarried a few kilometres west of Budapest in the Sóskút area. The weathering conditions were assessed not only by visual inspection by also by small-scale sampling and on-site diagnostics using non-destructive tests such as moisture content and strength. The latter was determined using Schmidt-hammer and Duroskop. The results confirmed that the sculpturist used an exceptionally high-quality, durable lithotype of porous limestone. The reddish discolouration of the stone surface was also analyzed using a portable XRF spectroscope. Weathering forms included black weathering crusts and missing parts, a few microcracks and the later use of stone inserts. The statues were dismantled and cleaned using poultices and at selected zone laser cleaning during the restoration works.