The changes induced to paper microstructure by accelerated ageing were studied using an automated gravimetric technique based on water vapour adsorption. The technique can be used especially in applications involving the adsorption and desorption of water, such as paper recycling, hornification, ageing and aqueous conservation treatments. The logistics for the calculation of the specific surface area of the examined samples are presented, and the f-plot technique was applied for the visualization and interpretation of the results. These indicated that ageing reduced the adsorption and the swelling capacity of the paper, resulting in a more compact structure, increasing crystallinity and promoting hornification.