Crepe rubber

Crepe rubber is coagulated latex that is rolled out in crinkled sheets and commonly used to make soles for shoes and boots but also a raw material for further processed rubber products.

After the collection of the latex milk, sodium sulphite (Na2SO3) or ammonia is added to prevent coagulation.

[1] Sodium para toluene thiophenate (an aromatic mercaptan) is often added as a bleaching agent.

[1] Colloidal latex is then mixed with formic acid to cause it to coagulate.

The coagulum is processed in a "creping battery", a series of machines that crush, press, and roll the coagula.