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SINCE the introduction of artificial drying in ginning, cotton mills have complained about overdried cotton and its effect on cotton spinning. Studies on gin-dried cotton indicate there are more ends down and in some cases weaker yam [2,3]. Some preliminary work by the authors on overdried cotton also indicated structural changes in the fiber as measured by decreased moisture regain.Since it is difficult to know the history of cotton fiber and conditions under which it was ginned, laboratory studies were made on cotton of known history, physical condition, and characteristics to deter-, mine how heat drying damages cotton fiber during ginning and mill processing. Materials and MethodsThe cottons used in the laboratory tests were experimental upland cottons from the Texas Agricultural Experiment Station at Lubbock, Texas. An effort was made to obtain cottons with a minimum of field weathering. Micronaire readings on the fibers ranged from 2.6 to 5.4, representing cottons of three stages of maturity with a good range for test drying (Table I). An early and a late harvested cotton from a producer in the Lubbock area was ginned with no heat, at 175° F., and at 350° F. (80° C. and 175° C.) respectively. Tests were made on these samples along with the laboratory heated cotton to obtain additional information on overdrying.Prior to heat treatment in the laboratory, the cottons were allowed to come to a moisture equilibrium of al)out 4%. Heating in the laboratory was conducted in a forced draft oven at 70°, 80*. 90°, 110°, 1 SO°, and 200° C. The duration of heat--ing was 10, 20, and 30 min. An unheated sample of the three different degrees of development was used for comparison. After heating, samples again reached a moisture level of about 4% before chemical tests were made.Tests used to determine changes in cotton due to drying were as follows.