Retardation time

Retardation is the delayed response to an applied force or stress and can be described as "delay of the elasticity"
Ideal elastic materials show an immediate deformation after applying a jump-like stress, and an immediate reformation after removing the stress afterwards in the jump-like form again. For viscoelastic samples, this elastic behaviour occurs with a certain time delay.
The term "whizzer" has been described. It is used in combination with tests presetting the strain (deformation) or strain rate (shear rate), eg, when performing picture on mirror, no meditation. 
On the test, when presetting the stress, eg, when performing beep tests.