The Italian definition of stucco marble is “scagliola ad imitazione del marmo”, meaning literally “scagliola with marble imitation”. It has a complex composition, and its many variations are a function of period, region and, probably, individual manufacturing practices. The main ingredients of stucco marble are gypsum (sometimes with the addition of lime), perhaps with additives (e.g. alum, borax), water, a binding medium containing protein and/or organic pigments and an organic surface coating to give it the characteristic high gloss. There are two different ways of colouring the stucco: addition of pigments to the glue (a method to obtain a uniformly dyed mass), or addition of dry pigments to the fresh stucco paste. To obtain the effect of a natural stone, small balls of paste in different colours are formed, layered, kneaded, and cut transversely. The ground for stucco marble is usually masonry, with plaster covered by the usual adjustment layer. The stucco marble layer is attached with glue while damp and pressed with a metal trowel (brass, copper or steel). The characteristic of the stucco marble technique is the special treatment of the gypsum mass that hardens when dry because of the addition of various substances. The paste has to be plastic enough to allow kneading and set hard enough to be polished and smoothed. The goal is to obtain on the one hand the highest degree of hardness of the stucco paste, and on the other, to retard the setting of the gypsum. Therefore, the primary requirement is the right calcination (burning) of the gypsum. Once the desired quality of gypsum powder is obtained, the next step is the setting in water: substances retarding the setting and facilitating hardening are added to water. The smoothness and glossiness typical of marble is obtained through grinding and polishing. The surface must be very well smoothed until it becomes hard. After scraping with a knife or a wooden spatula, holes or pores are filled with a mixture of gypsum and glue if necessary. After each grinding step this procedure must be repeated. The grinding is done with the use of a lot of water and various grinding stones. For additional gloss, oil is applied to the surface. When it is all smoothed, it must be left to dry and then rubbed down with a linen cloth. Further wax treatment is often added: in case, solid wax (or wax in turpentine) is applied to the surface, which is then buffed with a linen cloth. Stucco marble is frequently confused with stucco lustro which is based on lime plaster and belongs primarily to the fresco technique. Stucco marble was used to imitate marble in wall decorations, from the seventeenth to the twentieth century in Europe. Wittenburg (1999). [J. Cassar, R. de Angelis]