Applied with care, egg tempera emulsion paint forms the basis of a stable, easily removable retouching system. The whole egg is used, diluted with up to 50% purified water. Dry pigments are ground into the medium, further diluted with water and applied on top of previously sealed fillers. Changes in tonality occur during rapid drying by warmed air, light burnishing and saturation by a resinous varnish. More than one layer of retouching is required to obtain the desired effect.