Paper is as a fibrous network where the fibres are joined together in fibre/fibre crossings and the main constituents of the paper dry strength is the joint strength between the fibres and the strength of the individual fibres. To study the link between chemical properties of the interface between two fibres and the physical properties of paper the single joint strength between fibres was measured. The specific strength of each fibre/fibre cross and the influence of chemical treatment of the fibres could then be quantified.