The response of an industrial scale double drum dryer to variation of steam pressure, drums rotation speed and level (height) of the gelatinization pool between the drums is presented. To our knowledge, this is the first time that the gelatinization pool level is treated as an input variable. The output variables are the product's moisture content, mass flow rate and specific load (equivalent to the product's film thickness). The effect of the drum surface temperature and width of the gap between the drums on the behavior of the output variables is examined. A theoretical analysis is presented for the qualitative assessment of the basic process variables that control the film thickness of the product. The role of the thermal inertia of the drum wall to the response of the dryer is discussed. Changes in the thermal efficiency of the dryer are inferred from overall heat transfer coefficients.