ORIGINAL Surface modification of wood using friction Lauri Rautkari Æ Milena Properzi Æ Fre ´de ´ric Pichelin Æ Mark Hughes Received: 18 January 2008 / Published online: 27 September 2008 Ó Springer-Verlag 2008 Abstract The potential of linear vibration friction as an innovative means of producing increases in both surface density and surface hardness was explored. The influence of processing pressure and time on the degree of surface densification, surface hardness and surface elasticity was investigated. It was found that surface hardness (measured as Brinell hardness) was positively correlated with densification ratio. Furthermore, surface elasticity, that is the ability of the surface to recover elastically after indentation during the Brinell hardness test, could be increased by up to 33% depending on the degree of surface densification. The temperature rise due to friction was also studied. During processing, it was found that the temper- ature rise on both the radial and tangential surfaces was positively correlated with the processing pressure and time. Introduction By altering the characteristics of wood by, for example, resin impregnation accompanied by compression of the material, certain mechanical properties can be improved (Navi and Gigardet 2000; Gindl et al. 2004; Blomberg et al. 2005). Both impregnation and compression result in an increase in the density of wood that can lead to an improvement in its mechanical properties, in particular hardness (Navi and Gigardet 2000; Gindl et al. 2004; Zhang et al. 2006). L. Rautkari  M. Properzi  F. Pichelin Architecture, Wood and Civil Engineering, Bern University of Applied Sciences, Biel, Switzerland L. Rautkari (&)  M. Hughes Forest Products Technology (TKK), Helsinki University of Technology, P.O. Box 6400, 02015 Espoo, Finland e-mail: Lauri.Rautkari@tkk.fi 123 Wood Sci Technol (2009) 43:291–299 DOI 10.1007/s00226-008-0227-0