The upper divisions of wall panelling are especially suitable for a series of shields and badges when they are at a sufficient height to bring the heraldry above the line of the eye. This will probably be in carved work, the most direct and natural way of decorating wood, but shields in colour, flat or in relief, may occupy the panels with very satisfactory effect. A frieze is also an obviously suitable space for such a purpose, whether the decoration be modelled or painted, or both. Among the materials suitable for interior decoration gesso is an excellent means of obtaining relief in work that is to be painted, and it is more readily handled than modelled plaster, from the ease with which it can be kept moist. In early work the smaller details of monuments were frequently modelled in this material, as were the arms on some of the stone shields in Westminster Abbey; and on the decorative panelling, on which jewels and enamels were also modelled and painted. Gesso is simply the Italian name for Plaster of Paris, burnt gypsum, but is technically understood to mean a preparation of plaster or other material which depends for its hardening on the solidifying of some cohesive medium, usually a form of glue, and not on chemical action in the material. Methods of making gesso are described by Cennino Cennini in the MS., written in 1437, in which he describes minutely the technical practices of his time. First the plaster is to be “well washed and kept moist in a tub for at least a month” and is to be stirred up well every day until “it almost rots and is completely slaked and it will become soft as silk.” It was then made into cakes, dried and kept for use. By this process it became what was called gesso sottile, though the term is also applied to the similar preparation of whiting, to be mentioned presently. As to its use, it is directed to “Put some cakes of gesso sottile into a pipkin of water and let them absorb as much as they will. Grind it fine, mix it with fine glue in a pipkin, put the pipkin in water so that it becomes hot but does not boil, for if it did it would be spoiled.” A very important point is the thorough slaking and tempering of the plaster, which continues to improve the longer it is kept. The glue that was used was made from hides, size being made from the fine kinds of skin, vellum and parchment, as the finest kind is made now. Fish glue was also used from very early times.