Why the Fabric Underneath Your Head Matters at All
Cotton pillowcases have a short, irregular fibre structure. Under a microscope the surface looks like a field of tiny hooks. Hair cuticles, which are themselves layered scales lying flat along the shaft, catch on those hooks every time you shift in your sleep. By morning a single strand may have been snagged and released hundreds of times. The result is not dramatic breakage in one place but cumulative cuticle lifting across the length of the hair. Lifted cuticles scatter light instead of reflecting it, which is what dull hair actually is. They also let moisture escape faster than a sealed cuticle would.
