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.