Proplasma

Proplasma (πρόπλασμα), the first sketch for a work in clay, preparatory to its execution in bronze, marble, or other materials. We are told that the proplasmata of Arcesilaus, an artist of the end of the Roman republic, were sold to artists for higher prices than others' finished works; and Pasiteles spoke of plasticen matrem statuariae, &c. This was, however, a late practice. It was after the time of Lysistratus, the brother of Lysippus, that it was so general that nulla signa statuaeve sine argilla fierent. Even then, however, the artist did not, as in modern times, leave the execution of the statues themselves to skilled workmen. (Plin. Nat. 35.45.)

[E.A.G]