A parent glass in the SiO2–CaO–ZnO–B2O3–K2O–Al2O3 system, deposited and processed by the monoporosa firing method (1085 °C), was coated using a sol–gel procedure and by serigraphy with silica, bismuth oxide, zirconia, and anatase with thermal treatment at 600 °C. The photocata- lytic activity of the samples determined by degradation in the Orange II dye test shows that a first-order reaction according to the Langmuir- Hinshelwood model is followed. From the UV-Vis-NIR results the band gap calculated is around 3.5 eV for the parent glass and that with a silica coating, and slightly lower for the other coatings. The needle-shaped microstructure of the parent glass shows the best photocatalytic results in agreement with the literature. The preserved zircon microstructure can explain the relatively high results for the silica coating, which unexpect- edly showed better results than both the anatase and tetragonal zirconia coatings. Finally, the interaction with the parent glass can explain the relatively high results of the bismuth oxide sample