Hornification in cellulose-rich materials, such as wood pulps, reduces their ability to re-swell in water, weakening fibre networks and paper strength. This study explores a novel method to measure hornification and examines its underlying mechanisms. Hardwood and softwood pulps were subjected to sequential high-temperature drying cycles, with hornification assessed through water retention and xyloglucan adsorption. A strong linear correlation was found between decreasing water retention and reduced accessible surface area for xyloglucan adsorption. Distinct linear relationships emerged above and below 100°C, suggesting different hornification mechanisms at varying temperatures. Additionally, hornification reduced softwood fibre width and shorter fibre length in hardwood pulps.