Excavator bucket connectable to a boom has opposing side walls in a fixed position with respect to each other and each having a front edge and a back surface. The back surface is movable between a first position that substantially defines the capacity of the bucket, and a second position toward the front edges of the side walls. When the back surface is moved from the first position toward the second position, retainage that may be adhered to the interior side walls of the bucket is forced out of the bucket by the back surface.