Pitchers are pottery that has been broken in the course of manufacture.
Biscuit (unglazed) pitchers can be crushed, ground and re-used, either as a low-percentage addition to the virgin raw materials on the same factory, or elsewhere as grog.
Because of the adhering glaze, glost pitchers find less use.
[1][2] The crushed material can also be used in other industries as an inert filler.
Archaeologists call ancient pitchers sherds or ostracons; shards or ostraca.