Special Dyeing of Cotton on the Seed Gives Visual Evidence of Changes During Fiber Development

Abstract

A process of differential dyeing employed to distinguish between thick- and thin-walled cotton fibers has now been utilized to show visually that the drying of normal cotton fibers for the first time-as when the boll opens in the field -greatly affects their dyeing properties. The effect was observed as a pronounced color difference when one lock from a nearly mature boll, cut open in the laboratory, was dried and another lock was kept wet, and both were dyed in the same dye bath at the same time. The dried cotton dyed mainly red and the undried dyed green. The change in the cotton cellulose which caused the difference is undoubtedly submicroscopic, and takes place in addition to the changes visible in the microscope which are familiar in fibers that have dried normally on the plant. A significant feature of the submicroscopic change can be inferred from the dyeing behavior considered in relation to current views of the mechanism of direct dyeing—that is, undried fibers from a cotton boll are shown by a new tech nique to be more porous than fibers which have dried in the boll, and the thin-walled fibers in ordinary cotton are simi larly more porous than the thick-walled fibers, at least while wet in a hot dye bath. It follows that the differential- dyeing effect with cotton fibers is determined by cellulose structure in combination with specific properties of the two dyes employed.