Semi-empirical alternatives to the traditional Washburn equation have been used to analyse the mercury porosimetry data for a sol-gel silica and five alumina catalyst supports. A combination of different porosimetry experiments, including the conventional primary mercury intrusion and retraction experiment conducted on both whole pellets and a fragmented sample together with a mercury re-injection curve, have demonstrated that a sol-gel silica sphere possesses a so-called "skin-effect." This means that a thin band of narrow pore throats was located at the surface of the silica sphere guarding access to larger pores located within the interior. This particular interpretation of the raw data only became apparent when the new data analysis method was used. In addition, when an alternative expression to the Washburn equation is used to analyse the primary mercury intrusion curves for five alumina samples, the pore size distributions obtained all match a priori the corresponding distributions obtained from nitrogen desorption. This finding supports the view that both mercury intrusion and nitrogen desorption are invasion percolation processes.