Coloration of Mn in soda-lime silicate glass by X-ray irradiation was investigated as a coloration method suitable for glass recycling. Mn was initially reduced to Mn2+ With the addition of Fe, Sn or carbon, and the resultant colorless or near-colorless glasses containing no Mn3+ were studied. These glasses turned violet after X-ray irradiation and heat treatment at 200 degreesC due to formation of Mn3+. The color was stable at room temperature and decoloration occurred with heat treatment at 600 degreesC. The addition of Fe or Sn increased the optical absorption by Mn3+ ions. ESR measurement suggests that Mn photo-oxidation occurred through charge transfer from photo-induced hole centers. (C) 2003 Elsevier B.V. All rights reserved.