The rubber is formulated.
Combining the latex (except in latex-free applications) plus other additives
achieves specific qualities for the end compound. Compounds vary
according to the desired properties for the rubber bands.
The rubber compound is processed
through a machine called an "extruder" to form it into tube shape.
It's very similar to the way that manicotti noodles or other "hollow" pastas
are made...only the end result is a lot chewier!
A round pipe or "mandrel"
is placed into a length of the extruded tubing, and then it is subjected
to heat in a pressurized steam autoclave. This pipe forms the round shape
of the rubber band, and the heating process is referred to as "vulcanization."
Vulcanization causes a complex chemical change to occur in the rubber.
But in layman's terms, vulcanizing gives rubber its elasticity and other
desirable properties so that it's useful.
The rubber sleeves are removed
from the mandrel, and the vulcanized tubing is cut into "rings"
using a high-speed cutter. These rings are "rubber bands."
The rubber bands are thoroughly
washed and dried to remove chemicals used in the processing steps above.
After quality inspection, rubber bands are packed into bags or boxes for
distribution. Today, many rubber bands are also imprinted or receive
other "secondary" operations to improve their utility.