This book is one of a series reporting on international research and development activities conducted by the Schott Group companies. With the series Schott aims to provide an overview of its activities for scientists, engineers, and managers from all branches of industry worldwide where glass and glass ceramics are of interest. Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subject treated. This volume gives background knowledge about the difficult matter of electrochemical behaviour of glass melts and solid glasses, laying the foundations for - a sound understanding of physicochemical redox and ion transfer processes in solid or liquid glasses and the interpretation of experimental results; - control of production processes, including fining, interface reactions and thermodynamic equilibria of glass melts with refractories and the surrounding atmosphere; - the field-driven ion exchange between solutions and glasses or within electrochromic thin-film systems; - fundamentals and application of glass electrodes for pH measurements, as well as information about the presently ongoing redefinition by a IUPAC committee; - mechanisms responsible for glass corrosion; - the concept of optical basicity. The book is conceived as a monograph. The individual chapters, however, are written by experts from the Schott R & D department or their external partners in research. Many practical examples provide the reader with facts to study the various aspects of electrochemical processes in ion-conducting materials.