Macroporous alkali resistant glass has been developed by making additions of zirconia (ZrO2) and zircon (ZrSiO4) to the sodium borosilicate glass system SiO2–B2O3 Na2O. The glass was made using a traditional high temperature fusion process. Differential thermal analysis (DTA) was carried out to identify the glass transition temperature (Tg) and crystallisation temperature (Tx). Based on these findings, controlled heat-treatments were implemented to separate the glass into two-phases; a silica-rich phase, and an alkali-rich borate phase. X-ray diffraction (XRD) was used to identify any crystal phases present in the asquenched and heat-treated glasses. Fourier transform infrared (FTIR) spectroscopy also proved effective in investigating phase separation and crystallisation behaviour. After leaching, a silica-rich skeleton with an interconnected pore structure and a uniform pore distribution was observed. Pore characterisation was carried out using mercury porosimetry. The size and shape of the pores largely depended on the heattreatment temperature and time. ZrO2/ZrSiO4 additions increased the alkali resistance of the porous glass 3–4 times.