Cu-doped and Cu/Al-codoped high silica glasses (HSGes) are prepared by doping Cu2+ ions or codoping Cu2+ ions and Al3+ ions in porous glasses and then sintering at 1200 degrees C in air and the reduction of Cu2+ ions is observed in Cu/Al-codoped HSGes. With increasing the Al/Cu molar ratio, the color of the samples changes from brown to colorless gradually. Strong and broad glaucous emission from the monomer and dimmer Cu+ ions are observed when exciting the colorless samples with ultraviolet light. Absorption, photoluminescence, electron spin resonance (ESR) spectra and X-ray photoelectron spectroscopy (XPS) are carried out to investigate this phenomenon. The mechanism of this change is presented. (C) 2009 Elsevier B. V. All rights reserved.