  This paper discusses the possibility of identifying the shear and structure
relaxation kernels in glassy materials by means of a single, simple and
non-intrusive experiment. The material should be thermorheologically simple and
the kernels expressed in the form of Prony series. The experiment considered
consists in measuring the thickness variations over time of a flat sample
cooled symmetrically from both side from a temperature above the glass
transition temperature down to room temperature. The comparison of experimental
observations with theoretically calculated responses allows the identification
of the coefficients of the Prony series for the shear and structure relaxation
kernels using a least-square type method. This paper illustrates the success of
the method with `artificially' created experimental observations and with up to
two exponential terms in the Prony series for the shear and structure
relaxation kernels.
