Parts 1 and 2 of the ISO 289 describes the process of Mooney viscosity determination as well as the pre-vulcanization characteristics. The primary difference between the ISO and the ASTM Standard is this: ISO 289 has no provisions for specimen preparation on a mill. The ASTM method, on the other hand, allows the preparation of the milling specimen for a Mooney viscosity test. The use of milling may have an impact on different types of rubber. Thus, the test might produce different results.