AbstractNanoscale porosity is critical for cellulose reactivity and can be detrimentally affected by wet pressing. The present study evaluated how wet pressing reduced the nanoscale porosity of a set of pulps produced from sugarcane bagasse. The pulps were produced using hydrothermal treatments, followed by either 160 °C alkaline (sodium hydroxide) or 190 °C organosolv (ethanol-water) pulping. Pulping times (20, 40, 60, 80, and 100 min) and applied pressures in the pressing step (21, 43, 64, 85, and 107 MPa) were varied, and the resulting samples had their nanoscale porosity characterized using calorimetric thermoporometry. The lowest applied pressure (21 MPa) collapsed a considerable fraction of the nanoscale porosities. Otherwise, when additional pressure (up to 107 MPa) was applied, a much lower reduction in porosity was observed. The findings indicate that nanoscale porosity of pulps can be separated into compressible and incompressible components.