Transparent liquid without odor, taste or colour. The chemical combination is two parts hydrogen and one part oxygen. In the technique of painting, it is an indispensable element used as a vehicle for the mixing and diluting of colours for fresco and watercolour, as a solvent for glues and gums, and for the preparation of emulsions, etc. In restoration, it is employed as a solvent in numerous operations, and particularly in the interventions of cleaning mural paintings, drawings on paper, textiles, etc. In all of these operations, the water utilized must be pure, that is distilled or ionized, in order to avoid the inconveniences that may be provoked by the presence of salts and dissolved gas.