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 (Na<sub>2</sub>SO<sub>3</sub>) or ammonia is added to prevent coagulation.
When the latex arrives in the factory, sodium bisulphite (NaHSO<sub>3</sub>) or sodium metabisulphite (Na<sub>2</sub>S2O<sub>3</sub>) are added to prevent enzymatic reactions and discoloring.
Sodium para toluene thiophenate (an aromatic mercaptan) is often added as a bleaching agent.
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. The sheets are then hung in a heated drying shed and, after drying, sorted by grade and packed for shipping.
There are several types and grades of rubber crepe, mainly distinguished by the grade and pre-processing of the latex used in their manufacture.