[en] 18 contributions on application of natural science methods in tand conservation of cultural objects. One contribution is of INIS interest. (G.Q.)

[en] Samples from the weathered limestone of St. Stephen's Cathedral in Vienna have been analyzed using two different methods. Most samples show a weathering crust protecting the limestone. The chemistry of this crust was one of the most interesting points in this study. Sections through the limestone have been made for electron microprobe analysis. The microstructure and the chemistry of the crust was measured quantitatively. Scans across the boundary limestone/crust resulted in quantitative depth profiles. Many elementary distribution pictures taken in the vicinity of this boundary show clearly that the crust is very inhomogeneous already in small dimensions. The origin of this crust is explained as resulting from corrosion of the limestone with incorporation of windblown particles. Some of the distribution pictures (e.g. Al, Fe, K, Si) point to the presence of particles originating from outside the limestone (pure CaCO₃, with almost no inclusions). Since quartz particles, feldspathic particles, and rust particles are present in the crust, the only explanation is the incorporation from outside sources. Studies of the trace element chemistry of the crust and the limestone have been made using neutron activation analysis, incorporating 28 trace elements. Some of the elements are depleted in the crust, giving consideration to wash-out effects. In contrast, many elements are enriched in the crust. Most of these enrichments seem to stem from concentration effects of the original limestone during corrosion. Some elements, however, are introduced by acid rain or with dust, including Cl, Br, W, and Sb. In conclusion, the results point to a rather complex origin of the weathering crust, since no diffusion effects (like for S and Cl) from the crust into the limestone have been detected. The crust originated from incorporation of windblown particles, corrosion of the limestone, and incorporation of elements from the air and rain. (Author)