Softwood fibers pretreated with a monocomponent endoglucanase wereused to prepare a series of cellulose nanofiber qualities using amicrofluidizer and 2 to 34 MWh ton-1 of energy input. The specific surfacearea was determined for the series using critical point drying and gasadsorption. Although the specific surface area reached a maximum of 430m2 g-1 at 11 MWh ton-1, the nanofiber yield and transmittance continued toincrease beyond this point, indicating that more energy is required toovercome possible friction caused by an interwoven nanofiber networkunrelated to the specific surface area. A new method for estimating thesurface area was investigated using xyloglucan adsorption in pure water.With this method it was possible to follow the disintegration past the pointof maximum specific surface area. The technical significance of thesefindings is discussed.