Sheet packing is often times made in a press, like corrugated matting.
The varieties, however, known as gum core have to go through a
different process. Usually a core is squirted through a tube machine
and the outside covering of jute or cotton, or whatever the fabric may
be, is put on by a braider or is wrapped about it somewhat after the
manner of the old fashioned cloth-wrapped tubing. The fabric is either
treated with some heat-resisting mixture or something that is a
lubricant, plumbago and oil being the compound. Other packings are
made from the ends of belts cut out in a circular form and treated
with a lubricant. There are scores of styles that make special claims
for excellences that are made in a variety of ways, but as a rule the
general system as outlined above is followed.