This paper reports the preliminary results of a research aiming at assessing the consolidating and protective effectiveness of a water mixture containing lime water + acrylic emulsion + potassium siliconate. This mixture is particularly useful in the case of exfoliating and crumbling stone, such as Bologna sandstone, because it permits cleaning by pack technique after preconsolidation and does not produce a darkening effect. Consolidation effectiveness was assessed by measurements of ultrasonic velocity tests carried out both in situ and in the laboratory, and by determinations of pore-size distribution. The agreement of laboratory and in situ results confirms the usefullness of the ultrasonic non-destructive testing for evaluating the filling of the pores and therefore the consolidation effect of a treatment.