A comparative study of different formulations of poultices for soluble salts removal from experimental plasters

Soluble salts extractive capability of some commercial materials currently used in plaster restoration sector (ArbocelTM plus sepiolite; ArbocelTM, sepiolite and sand; Westox-Cocoon®) were tested in the present study, with the aim to evaluate their efficiency, their compatibility with the substrates as well as in terms of costs and duration of intervention. The three poultice products were first characterized in terms of porosimetric distribution. The desalination tests have been performed on samples of plaster specially formulated and made at the laboratory. Experimental specimens were then brought into contact with a solution of Na2SO4 0.3 M. The efficiency rating of these different types of poultice products was carried out, for the whole duration of the test, by means of ion chromatography and electrical conductivity measurements performed on obtained solutions. Between the tested products, Westox-Cocoon® showed the best efficacy in terms of soluble salts extractive capability while the other two products, which were successfully used in previous experiments (Montana et al., 2014), did not have the same positive results in this case study. Furthermore, in a real system it is also necessary to take into account other factors such as easiness of application, capacity of the various poultices, compatibility with the substrate and cost/benefit ratio. Being fully aware that the proposed approach is still preliminary, this paper provides a practical example of standardizing a survey methodology for evaluating the efficiency of salt extraction methods from porous building materials.