This work looks at a range of copying processes used between 1950 and 1970 and which can be gathered under the heading 'Thermography'. Thermography is a broad term covering those processes which utilise heat to produce their image. The main aims of the work were: to examine how and when each process was used; to determine the chemistry of each process; to examine the permanence of existing copies produced using the various processes; and to look at possible ways of improving the preservation prospects of these copies. These aims were addressed through both primary and secondary research mechanisms. Research included examination of documentary source material, seeking out persons with first hand knowledge of the development of the processes, as well as analysis of extant copies from the various processes. Finally a series of preliminary experiments into the aging properties of the papers and the possibilities of preservation through the use of protective materials were carried out.