or preparation, sizing, priming. Layer or several initial layers of material applied to the support in order to obtain a proper surface to receive painting pigments. If the ground consists of several layers, the final layer is commonly known as the imprimatura or priming (v.), in modern literature. The ground of panel paintings and paintings on canvas generally consists of white, calcium-based mineral substances - like gesso or crete white - and of adhesives with an animal glue base. The quality of the materials used and the correct execution of the ground is fundamental for the conservation of the painting throughout time. Due to the location of the ground between the support and the pictorial layers, the ground's binder must contain a sufficient absorbent capacity, for permeability and elasticity. This is in order to respond to the movements of expansion and contraction of the support, thus limiting the transmission of the pictorial layers. The practices are described in full length by Cennino Cennini, who in stating the various fundamental stages for a ground made of gesso and glue, hands down traditional customs of the Mediterranean countries.