It is true that "Nothing is more practical than theory" as Boltzmann said. Provided - however - that the assumptions on which The theory is founded are well understood. But. indeed. engineering costly experience shows that "Nothing can be more disastrous than a theory" when applied To a real task outside of practical limits of the assumptions made. Because of an homonymous identity with the considered problem. J.T.P The growing interest in Isodyne Stress Analysis and the related experience of the author show that the major monograph and reference book on the subject, Isodyne Stress Analysis by Jerzy T. Pindera and Marek-Jerzy Pindera, [27], does not of contain sufficiently detailed data on the theories and techniques experimentation. The purpose of this work is to close this gap. Thus, this work is an extension of Isodyne Stress Analysis and complementary to it. Consequently, only a short outline of the theory ofisodynes is given in Chapter 2. Only the basic concepts and relations are presented to provide the link between the underlying analytical and optical theories and the experimental techniques. One of the major purposes of a preface is to formulate and explain the chosen frame of reference in a condensed form, even when some components of it are discussed in the text. A main issue of the underlying frame of reference pertains to the roles of the abstract thinking and of the observation in cognition of reality.