Determination of cotton fiber maturity and linear density (fineness) by examination of fiber cross-sections. Part 1: Comparison of two image analysis systems used in conjunction with optical microscopy

Researchers from the United States Department of Agriculture and Texas Tech University have published the establishment of a set of reference cottons with known fiber maturity and linear density (fineness) values. Their work was based on careful analysis of the dimensions of a large number of individual transverse fiber cross-sections viewed under the optical microscope to obtain representative values for a particular cotton. Since this set of reference cottons has a high potential value for instrument developments and the world’s cotton industry in general, it was considered useful to independently test both the processes used and the assigned values for this set of reference cottons. Using independently developed software, a careful cross-section by cross-section comparison with the original data identified that the measured fiber perimeter values were in good agreement. However, cell wall area values and, consequently, the fiber maturity (theta) and fineness values were consistently smaller. The difference ranged from up to 40% for the small cell wall area values down to 15% for the larger cell wall area values, with the average difference being approximately 20%. These differences stem from a different interpretation of the outside boundary of the fiber cross-section by the two image analysis systems due to the limited optical resolution of the captured images. This implies that while the ranking of fineness and maturity values originally assigned to the reference cottons is likely to be correct, there may be a significant systematic error in the assigned values of the cell wall area and hence fiber maturity and linear density values.