From The Collaborative International Dictionary of English v.0.48 [gcide]:
Depolishing \De*pol"ish*ing\ (d[-e]*p[o^]l"[i^]sh*[i^]ng), n.
(Ceramics)
The process of removing the vitreous glaze from porcelain,
leaving the dull luster of the surface of ivory porcelain.
--Knight.
[1913 Webster]