Dissolution of salts crystallised in building materials using ultrasound: an alternative to NORMAL (1983) standard methodology.
Our aim in the present work is to extract salts from ornamental stone using a faster and less tedious method than the customarily used NORMAL method [NORMAL, Dosaggio dei Sali Solubili, CNR-ICR, Roma, Italy (1983) 13/83]. For extraction in aqueous medium, the latter method requires shaking for 72 h at a temperature of 60 degrees C. Our aim is to attempt to shorten this time to less than 1 h using ultrasound. The results of the present study indicate that there is a good correlation between the amount of salts extracted applying the method described in the NORMAL (1983) normative and the amounts extracted with the method proposed here, subjecting the material to ultrasound (50 KHz) for 45 min.
An integrated analytical approach to diagnose the conservation state of building materials of a palace house in the metropolitan Bilbao (Basque Country, North of Spain).
Raman microprobe spectroscopy and microX-ray fluorescence were used to analyse the original composition and degradation products of the limestone and the sandstones from the facades of one historical building. Carbon particles, gypsum (CaSO(4).2H(2)O) and some nitrate compounds were determined by Raman measurements, while elemental characterisation carried out by microXRF revealed the presence of lead, sulphur and copper as pollutants. On the one hand, the grey sandstone is the most deteriorated and in some cases pollutants reach 3 cm depth. On the other hand, quantification of soluble salts (chlorides, sulphates, nitrates, nitrites, fluorides and carbonates) was accomplished by ion chromatography. Chloride and sulphates are not significant soluble salts in the façades of the building, but the amount of nitrate is even 136 g kg(-1) in some of the most deteriorated samples and of 147 g kg(-1) in black-crusts. Finally, organic compounds (mainly PAHs) were characterised by GC-MS. Concentrations higher than 20 ppm of total PAHs were measured in the black-crusts of the rain-protected facades. The presence of certain PAHs indicated combustion of fuels as the main source of deterioration for the palace house building materials.
Salt weathering on monuments
A detailed discussion of the mechanisms of salt crystallization in stone : the evolution of salt systems on walls, and the relation between room climate and salt crystallisation. A methodical approach to monitoring wall paintings affected by salt weathering is presented with the case study of the church of the Mustair convent (Switzerland). A first restoration was carried out on the fresco mural paintings in 1947-1951 and afterwards, the decay due mostly to salt concentrations and crystallization, increased. Research showed that this was due to reactions produced by alkaline materials introduced during the restoration. The preservation measures include: control of humidity by installation of a trench around the outside foundations, new gutters and protection from melting snow; desalination of the paintings by application of wet blotting paper on the surface; monitoring of the room climate.