1. What Is Vacuum Metalizing As can most probably be deduced from the name, the term ‘ metalising ’ (also spelt as ‘ metallizing ’) is used to describe the process of coating a thin layer of metal onto the surface of a non-metallic substance. One of the oldest known examples of such a process is the technique of ‘silvering’, a practice first used in the nineteenth century by the German chemist Julius von Liebig, and which has been used ever since in the process for the manufacturing of mirrors.