View of two engineers, Stanley Bilker (background) and Ralph Harper (foreground), operating the calender sheeting machine at the the Naval Air Experimental Station's Rubber Compounding and Processing Laboratory. The calender was a National Rubber Machine 6" x 12" three-roll type used to process rubber into continuous sheets of a pre-determined gauge and to friction and coat fabrics. Roll temperatures ranged from 50 to 350 degrees Fahrenheit and were controlled manually by circulating water, steam, or a mixture of both. This photograph was included in a 1949 Naval Air Experimental Station report on compounding rubber.