ISO 6914:2013 describes three methods for the measurement of the change of stress in a test piece at a given elongation for the purpose of determining the ageing characteristics of a rubber.

Method A is intended for measurement under continuous strain conditions.
Method B is the preferred method for measurement under intermittent strain conditions.

In the case of both methods A and B, a stress relaxometer is used to record the stress at the temperature of ageing.
Method C is an alternative to method B for measurement under intermittent strain conditions in which the test piece is removed from the ageing environment for measurement of the stress at standard laboratory temperature.