Ion implantation is a powerful technique to modify the contact angles of surfaces. However, a change of the contact angle with the passage of time, called ageing, is observed on most surfaces. This paper aims to better understand the mechanism leading to the ageing of quartz surfaces implanted by argon ion. Coupons of quartz have been irradiated by 3 keV Ar ions to a fluence of 1.8×1016 Ar cm−2. Some implantations were performed under oxygen partial pressure (∼5×10−5 Torr). The samples have been characterized at different periods of time after implantation by means of contact angle hysteresis measurements, angle resolved x-ray photoelectron spectroscopy (ARXPS) and lateral force microscopy (LFM). A more hydrophilic surface was observed immediately after implantation. This effect was strongly enhanced by the use of an O2 partial pressure. With the passage of time, the contact angles increased both in ambient air as well as under an Ar atmosphere. Characterization by means of XPS has shown a decrease of the relative concentrations of the more polar molecules containing oxygen (C–O, C = O and (O–C = O)–O) which could partly explain the increase of the contact angles with time. On the other hand, a higher ratio of the signals SiO2(104 eV)/SiO2(103 eV) is observed for samples implanted with O2which could be responsible for their higher level of wettability. A model using the ARXPS measurements suggests that for the samples implanted without oxygen, the ageing could also be caused by the spreading of a natural carbonaceous surface layer dispersed into islands after the Ar implantation. This layer being more hydrophobic than the SiO2 surface, its spreading would increase the contact angles. Characterization by means of AFM–LFM shows that the surface is composed of two areas having different friction properties. Their distribution is in agreement with the covered surface fraction given by the model for the samples implanted without oxygen and aged in Ar.