In the masonry of the pyramids plaster is constantly used, both to fill joints as a bedding, and to level up hollows in a face. The plaster used is a mixture of ordinary lime and plaster of Paris, the carbonate and sulphate of lime. How it was introduced into the joints of the pyramid casing is a mystery. The blocks at the base weigh sixteen tons, so that no free sliding to reduce the joint-filling could be done; yet the vertical joint, five feet high and seven feet long, is filled with a film of plaster only a fiftieth of an inch thick. The joints of the masonry in the passages and chambers are all filled with plaster, though so close as to be almost imperceptible. In the core masonry a coarse plaster was poured between the stones and filled into hollows. The flaws and defects in the faces of stones were freely filled with plaster, which was coloured to match the stone. In rock tombs plaster was used to fill up cracks and hollows; and it often remains in perfect condition while the rock around has decayed.
Plaster was also used on the brick walls, which were faced with a hard coat about a tenth to a sixteenth of an inch thick, upon which paintings were executed. By the XVIIIth dynasty this became a mere whitewash over the mud-facing of the wall. In the roughly-hewn rock tombs of that age at Thebes, the jagged surfaces were smoothed by a coat of plaster, often two or three inches thick in the hollows. A strange use of stucco was for a thin coat over sculpture, as a basis for colouring. Such a coat was even laid over statuary. In all ages this hid to some extent the full detail of the sculptor's work in reliefs. In the XIIth dynasty the finest lines were hidden by it; and on coming down to the Ptolemaic times the plasterer ignored all the sculpture below, filling the figures with a smooth daub of plaster on which the painter drew what he liked. It seems strange why the sculptors should have continued to put fine work and detail on to a surface where they were going to be at once ignored. It suggests a rigid bureaucracy in which the sculpture had to be passed by one man, and the painting by another, without any collaboration.
Stucco was used for independent modelling, as in Italy. It was laid on a flat canvas base, stretched over wood, and the whole relief was in the stucco. The chariot of Tahutmes IV is one of the main examples of such work, of which a small portion is shown in fig. 132. The relief is low and smooth, and full of detail; there is none of the sketchy rough tooling, as seen in Roman stucco reliefs. Minute details of dress and hair are all tooled in, and supply some of the best studies of Syrian robes. The varying patterns on the shields of different branches of Syrians, the feathering of the arrows, the shape of the daggers, and the flowers of the papyrus and lotus of north and south, are all most precisely rendered. It would be hard to find any point in which more details could be introduced.
Plaster was also used for casting in moulds, and for making moulds. The death mask of Akhenaten shows how such castings were produced in the XVIIIth dynasty, from a single mould without any undercutting, to serve the purpose of the sculptor as a model. Of later examples of such castings we have here a lion's head and a king's head (figs. 133, 134). They were probably made to be supplied as school copies to the workshops where the sculptors were trained. Plaster moulds are very common at Memphis, and it is said they were even used for casting bronze work. This is very doubtful, as plaster is reduced to powder at 260°C, while moulds for bronze casting must be heated to 15000 to 18000 C.; they are more probably for casting pewter. Plaster moulds were also used for moulding pottery lamps. The oiling of plaster was done on painted plaster statuettes, so as to make them waterproof. They can still be scrubbed in water without disturbing the colour.
132. Stucco relief modelling (XVIIIth dynasty).
134. Plaster castings for studies.
The most artistic use of plaster was for the modelled heads, which were placed on mummy cases in Roman times. Though most such works were rather crude, some are found which show real ability of portraiture. In fig. 135 we have a sympathetic study of the face of a young man. The lips are beautifully true, the modelling of the cheek is quite natural, the nose and brow well formed; only the eyes have been left blank, and marked afterwards with colour. The head, fig. 136, is evidently a careful study, giving the cautious, cold expression of the man. Another face (fig. 137) is subtle, and full of feeling: the faint smile on the lips, the gracious contour of the cheek, the wavy hair, give a memory in death of a real personality. The only jarring feature is the square brow, copied from an unfortunate convention in Greek art. The eyes are here again left blank; but they seem to have been intended to be open, by the slight ridge of the raised lid. Was there a convention of regarding the dead as incapable of seeing, though seen by memory? How far these modelled heads were portraits is answered in a curious way by fig. 138. The light outline there is that of the plaster modelling, the dark outline within it is the skull from the interior of the coffin. It will be seen how exactly they agree; there is a thin skin over the forehead, then a fleshy part to the brow. Along the bridge of the nose the model closely follows the bone; below the nose the angle of meeting of the jaws exactly agrees, leaving a uniform thickness of lips; and lastly, the fleshy fulness of the chin is seen projecting. This agreement is one which the artist could never have expected to be thus tested, and therefore gives us the more confidence in his skill.
137. Modelled heads.
138. Modelled head and skull.