A plaster cast produced from a mold, reproducing the surface of an original sculpture or model.
Calco in gesso is a plaster cast taken from a mold. Unlike the negative mold itself, the cast is a positive reproduction of the original surface.
Plaster casts have been used for workshop reference, teaching, replication, preservation, study, and the transfer of sculpture from one material or scale to another.
Etymology
Italian: calco, “cast/impression,” + gesso, “plaster.”
Sculptor Notes
The distinction between forma and calco is fundamental: the mold is negative; the cast is positive. Confusing the two obscures the actual sequence of sculptural reproduction.
References
https://www.treccani.it/enciclopedia/calco/; https://www.treccani.it/enciclopedia/forma_res-0d8dd9eb-8baf-11dc-8e9d-0016357eee51_%28Enciclopedia-Italiana%29/; https://www.supsi.ch/it/nuova-luce-su-un-maestro-della-scultura-come-vincenzo-vela