The emulsion layer is manufactured in a series of kettles for mixing, digesting, and blending. In each process, thermometers record temperatures to ensure they fall within a certain range and are constant to yield a high quality, uniform product. First, halide salts with emulsifying gelatin are placed in kettles and silver nitrate is poured in to make a solution of silver halide. Next, the emulsion is digested and following that, more gelatin is added and the mass is cooled in a refrigerating room until it has the texture of a stiff jelly. This is then processed through a machine to be cut up into shreds and then repeatedly washed. When washing is complete, the shreds are drained, and passed through a vacuum filter to eradicate dust and dirt. Finally the emulsion is melted and spread over the cellulose-nitrate base using special equipment.

 

These machines, such as the Coating Machine Head diagrammed above, are located in long alleys where only washed and conditioned air is permitted to enter; air conditioning methods regulate subtleties in the temperature and control the humidity of the air along the alley as the base is coated with the emulsion and then the long sheets of film slip over a chill roll and are carried down the alley in festoons for drying and curing. The film then proceeds to the slitting machines to be cut into the appropriate width for motion pictures.