Photoelasticity has been used for decades in the experimental measurement of stresses and strains. As data-acquisition techniques only identify the differences between principal stresses and strains, stress-separation techniques exist to identify each of their values separately. A variety of techniques have been developed since the early days of photoelasticity, aiming to automate the measurement process, to exploit the full potential of photoelastic methods, and to facilitate its application. The purpose of this paper is to provide a general overview of the different stress-separation techniques, and their current state of development and usage. The paper presents the publications and the authors who have contributed to the development of new techniques.