CALCO. - It is the reproduction of objects worked in relief, obtained by means of impressions taken from the original with wax, clay, plaster, or another suitable material. The material most commonly used today for making casts is plaster (a special quality for moulders).
The practice of making casts is very ancient; the ancient Egyptians seem to have known II. Luciano, Plutarco, and Giovenale refer to it in their writings. During the Renaissance, papier-mâché or scagliola was also used to make casts of objects, especially those in relief. Also frequent were coloured or gilded casts representing sacred images. Renewed interest in antiquity spread the practice of making casts of ancient sculptures; collections of casts are found in museums and galleries and in schools of archaeology and art history; the oldest of these collections is that begun in Milan by card. Federico Borromeo at the Ambrosiana for artists and scholars.
To reproduce graffiti, especially inscriptions, casts are made with blotting or filter paper or, better still, with the appropriate so-called « carta da c. ».