The negative mold that records the inverse surface of a sculpture and receives casting material to produce a positive replica.
Forma in negativo is the negative mold produced during formatura. Every projection of the original becomes a recess in the mold and every recess becomes a projection.
Once prepared and treated with an appropriate release system, the negative mold receives plaster, wax, or another casting material to create a positive cast.
Etymology
Italian: forma, “mold/form,” + in negativo, “in negative.”
Sculptor Notes
Thinking in negative form is a specialized sculptural intelligence. Undercuts, seam placement, keys, sections, and the order in which pieces are removed determine whether the original and the cast survive intact.
References
https://www.treccani.it/enciclopedia/forma_res-0d8dd9eb-8baf-11dc-8e9d-0016357eee51_%28Enciclopedia-Italiana%29/; https://www.treccani.it/enciclopedia/calco/