Abstract Research of correlations between insulator macroscopic properties (electric strength, mechanical toughness, friction, radiation damage sensitivity, etc.) has shown that parameters related to polarization and energy dissipation processes are relevant for these properties. The investigation of the charging effect under an ionizing beam could be a way of characterizing polarization and relaxation processes leading to breakdown, fracture, etc. The physical basis which allows to understand the degree of insulator charging phenomena is reviewed. A universal concept of trapping as well as the nature of the energy which is stored in a charged dielectric are recalled. Basic principles of charging and detrapping were verified on well defined materials. It was observed that the relaxation of the mechanical energy consecutive to an abrupt variation of the polarization is a major cause of defect generation leading to failures. Results achieved by electron spectroscopy are reviewed. It is shown that there exist spectroscopic observations which can be related to parameters governing electric and mechanical strengths.