This paper reports on a long-term research programme undertaken at Camberwell College of Arts, which aims to study in detail the effects of aqueous conservation treatments on the mechanical properties of paper. Consideration is given to the material nature of paper and the difficulties associated with paper testing. Emphasis is placed on the need for careful specimen preparation and the control of test conditions. The results of a preliminary study on the effects of washing paper are reported. The main changes observed were a reduction in the elastic modulus, and an increase in the extensibility, compared to untreated paper. These changes were attributed to a relaxation of frozen-in strains and a reduction in the proportion of fibre bonding area of the paper sheet. No significant difference between the tensile strength of paper before and after washing was observed.