The rubber is then shipped to a rubber factory. Here, the
slabs are machine cut (or chopped) into small pieces. Next,
many manufacturers use a Banbury Mixer, invented in 1916 by
Femely H. Banbury. This machine mixes the rubber with other
ingredients—sulfur to vulcanize it, pigments to
color it, and other chemicals to increase or diminish the
elasticity of the resulting rubber bands. Although some companies
don't add these ingredients until the next stage
(milling), the Banbury machine integrates them more thoroughly,
producing a more uniform product. 5 Milling, the next phase
of production, entails heating the rubber (a blended mass
if it has been mixed, discrete pieces if it has not) and squeezing
it flat in a milling machine.
