Clay Poultices in Salt Extraction from Ornamental Stones: A Statistical Approach

Maria Angeles Vicente1, 3 and Santiago Vicente-Tavera2, 3
1 Departamento de Química y Geoquímica Ambiental, IRNA/CSIC, Salamanca, Spain
2 Departamento de Estadística, Universidad de Salamanca, Salamanca, Spain
3 Unidad Asociada CSIC/Universidad de Salamanca, IRNA, Apdo 257, 37071, Salamanca, Spain
E-mail of corresponding author: svt@gugu.usal.es

Abstract: The extraction of salts by layered (bentonite) and fibrous (sepiolite) clay poultices from stone materials currently used in Heritage buildings was studied. Analyses were performed on stones affected by salts but not submitted to humidity, and also on stones affected by salts and simultaneously submitted to continuous or intermittent humidity during the salt-extraction process. From the experimental results and the statistical analysis, the application of two successive poultices is sufficient for an efficient extraction of Cl and NO3 in the absence of humidity. However, under humid conditions, the efficiency of the method is reduced considerably. For SO42−, the use of hydrotalcites (anionic clays) is recommended for more effective extraction.

Key Words: Bentonite • Conservation • Historical Heritage Buildings • MANOVA-Biplot • Ornamental Stones • Poultices • Salts • Sepiolite • Weathering of Stone

Clays and Clay Minerals; June 2001 v. 49; no. 3; p. 227-235; DOI: 10.1346/CCMN.2001.0490305
© 2001, The Clay Minerals Society
Clay Minerals Society (www.clays.org)