On the technique of making thin celluloid films

The paper deals with the technique of making celluloid films of thickness of the order of the wave-length of light. In the first part the forming of celluloid films upon the surface of water is described. By this means films as large as 7 by 3 cm., of thickness of the order of 500 Å., were formed. These films, however, were not vacuum-tight. The preparation of films upon a clean mercury surface is then described. These were vacuum-tight to a difference of pressure of several cm. of mercury between the two sides. A description of an apparatus for testing the vacuum-tightness of the films and the maximum pressure that they could support without breaking is given. Further, methods of making coloured films and of forming metallic mirrors upon the surface of the celluloid films by metallic evaporation are discussed. An experiment to see if the films exhibited any "structure" by X-ray analysis gave no results.