The flue curing process for tobacco is practiced today in nearly the same manner as when tobacco first became of commercial importance, with no definite procedure being followed. A scientific study has proved that the curing process is accurately defined within narrow limits, and that control rather than art may be more definitely relied upon.

Tobacco curing differs from a true drying process in that both physical and chemical changes are involved. Since it is impractical to evaluate the chemical changes because of their complexity, the physical changes were investigated, for they govern both the chemical and physical changes which take place.

Drying rate curves for each period of the curing process were obtained over a wide range of constant conditions of temperature, relative humidity, and air velocity. Correlation of these curing curves indicate the narrow limits of the conditions required for satisfactory curing, and the critical points beyond which resulted in poorly cured tobacco.

From the results obtained, air conditioning improves the process by (1) reducing the time approximately one-half, thus doubling the capacity of the barns; (2) the production of uniform quality tobacco completely eliminating loss from improper curing; and (3) large reductions in labor and fuel requirements.