PURPOSE: To conduct high density paste filling into porous hoop, powder filler is fed to the porous hoop downstream a gate whick is located downstream of the filling device and spaced a little from the surface of the hoop.

CONSTITUTION: A gate 13' is located at the end of paste filling device and spaced from the hoop surface 1 by a small gap 25. So brushes 8 of the brushing unit 7 forms a thin paste layer 3' on the surface of the hoop 1. A powder feeder 18 is located downstream the gate 13' and supplies powder whose composition is the same as liquid-removed paste. As a result, the thin paste layer 3' becomes highly viscous layer 26, which is then rubbed into the hoop 1 by use of a number of brushes 19 of brushing unit 20.