Investigations using microscopy and x-rays were carried out on sound rocks (trachytic and trachyandesitic tuffs, and pumices) and weathered parts (crusts and honeycombs). The physical characteristics of weathered and unweathered samples (water or solvent absorption, drying, and capillarity) were measured in view of the two most important parameters for in situ conservation of the moai (moisture and physical characteristics of the crusts). Measurements of superficial moisture on moai were made to locate the damp areas that define treatment conditions. These have to be developed in laboratory trials. Some nine products (consolidants and/or water repellents) were tested by artificial weathering following meteorological data. The final selection was based on the results from classical tests. Some treatment conditions are defined.