Science: Rubber from Rubber

As scrap rubber piled up in reclamation heaps last week, many a citizen wondered how—and even whether—you could separate the rubber from a raincoat. It is possible and simple, explained rubber technologists last week.

In rubber-reclaiming plants the scrap is first sheared and hashed into tiny pieces.It is then sifted past magnets, which draw out any bits of iron. Next it is dumped into a "digester" tank where 1) caustic soda (sodium hydroxide) is added to destroy all cloth fibers and to remove free sulfur (added originally in vulcanizing); 2) coal-tar oils are added to soften the rubber. These added chemicals...