This document establishes the methodology to measure the quantity of water absorbed by a defined surface of a porous inorganic material used for and constituting cultural property, by contact sponge method. The method can be used on porous inorganic materials which are untreated or have undergone any treatment or ageing. The method can be used both in the laboratory and in situ on flat surfaces. NOTE 1 Treated materials are those which have been subjected to cleaning; to the application of water repellent, consolidating and/or biocidal products; to artificial aging tests, etc. NOTE 2 The test is not intended to be used on surfaces which are severely deteriorated, where application of the sponge is likely to cause material loss. The operator is expected to ensure good contact with the perimeter of the container. The test is not accurate when applied to rough surfaces.