The object of this operation is to fill all fissures or cracks in the picture with a composition which is capable of receiving a coating of paint without absorbing it. The composition employed for this purpose consists of a mixture of size and whiting, to -which a small quantity of black is added to give the composition a neutral tint. The " stopping'" as this mixture is called, is pressed into the cracks by means of a palette-knife, care being taken that every fissure is well filled with it. The picture must now be set aside for several days to allow the stopping to become gradually but thoroughly dry. The next operation is to remove the superfluous stopping, which is effected by rubbing the surface of the picture with soft or " velvet" cork moistened with water. The cork must be applied gently and with a circular motion, so that, while removing the superfluity, the cracks may be left perfectly level.