|1.||a white ground of plaster and size, used esp in the Middle Ages and Renaissance to prepare panels or canvas for painting or gilding|
|2.||any white substance, esp plaster of Paris, that forms a ground when mixed with water|
|[C16: from Italian: chalk, |
(Italian: "gypsum," or "chalk"), fluid, white coating composed of plaster of paris, chalk, gypsum, or other whiting mixed with glue, applied to smooth surfaces such as wood panels, plaster, stone, or canvas to provide the ground for tempera and oil painting or for gilding and painting carved furniture and picture frames. In Medieval and Renaissance tempera painting, the surface was covered first with a layer of gesso grosso (rough gesso) made with coarse, unslaked plaster, then with a series of layers of gesso sottile (finishing gesso) made with fine plaster slaked in water, which produced an opaque, white, reflective surface
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