The tubes are then taken to the bottom-forming operation
as required by the particular specification of sack they will become.
Some are sewn closed, making sewn open mouth or sewn valve sacks. The
tubes are placed in bundles on automatic feeders which deliver them
one at a time at speeds of 30 to 50 sacks per minute.
Other tubes are taken to a pasted bottomer and form either
a pasted open mouth, stepped-end pasted valve or a pinch bottom open
For example, the valve sack is pasted closed at both ends
during manufacture with only a corner opening or valve at one end,
through which the sack is filled.