Renewed interest in mercerization as a pre-treatment for textile finishing has led to research on the effects of temperature on this process. Mercerization, the swelling of cotton in caustic soda, causes changes in crystallinity from a Cellulose I structure to a Cellulose II structure, along with changes in fiber physical dimensions, increased dyeability, luster and tensile strength. These changes are differentiated by light microscopy, image analysis and FT-IR, and transmission electron microscopy. Cotton yarns were mercerized with an aqueous solution of 23% NaOH and 1% wetting agent. The yarns were treated for 1 hour at 0, 20, 60, 80, and 110° C, and washed in distilled water at the same temperature as the treatment bath. Rapid embeddment procedures have been developed for analyzing the effects of treatments on cotton fiber structure. Cotton fiber cross-sections were prepared for light microscopy/image analysis by encasing the fibers in a tube,1 embedding in mefhacrylate plastic (Fig. la), polymerizing for 30 minutes with UV, and sectioning.