Glasses from the Na2O-B2O3-SiO2 system, doped with Al2O3, ZrO2 and TiO2, were thermally (in the temperature range of 420-700 deg C) and chemically treated. During thermal treatment, separation of the borate phase from the silica skeleton occurred resulting in the formation of an interconnected microstructure. The borates were in the form of small drops jointed to each other. In the course of chemical treatment, the borates were leached in water and water solutions of acids or bases with the glass becoming very porous. The experiments showed that ZrO2 and TiO2 caused an increase in pore diameter at definite leaching times. Al2O3, however, decreased it, so that glasses doped with Al2O3 have a greater specific surface. In this case a double-pore distribution occurred.
