an air chamber 45 located beneath the coarse mesh screen or perforate plate 23 of the microwave oven 11 in this manner the heated up air passes into the microwave oven 11 and ensures further heating of the cotton bale 12 and the removal of water vapor escaping as a result of the heat treatment of the cotton bale 12 such water vapor initially ascending to the connecting pipe or stud 17 and then being suction extracted by a blower or fan generally indicated by reference numeral 50 the microwave generators 25 each preferably have a maximum power output of about 1 2 kilowatts and this means that with a total of twelve microwave generators 25 it is possible that a cotton bale 12 weighing approximately 220 kilograms and having an original 6 water content can be dried in about 14 minutes to have a residual moisture of 4 water if even dryer cotton is required for instance cotton with a residual moisture of 1 the treatment time is extended to about 35 minutes it is actually not the residual moisture in the cotton itself that is important what is important is that the moisture of the honeydew deposits or contaminants which moisture may initially be much higher than the average moisture in the cotton bale 12 is itself reduced this being particularly favorably achievable by means.