Development of diffuse double layers in column-wicking experiments: Implications for pH-dependent contact angles on quartz

► Applying the classical Washburn equation contact angles show a minimum at the iep. ► Permeabilities and rate of capillary penetration are influenced by pH changes. ► Changes in permeability can be explained by an electroosmotic counter-pressure. ► An equation is derived, taking account for electroosmotic counter-pressures in capillary rise. ► Applying the derived equation results in expected contact angle-pH patterns.