Chemically inert and different coloured glasses were prepared by inserting up to 10 wt.% steel plant fly ash into different kinds of inorganic matrices. Three different matrices were tested: municipal incinerator grate ash, glass cullet and a low cost CMAS devetrifiable glass. The experimental techniques used to characterise both the starting and the heat treated (glass-ceramics) glasses were differential thermal analysis, durability and release tests, X-ray diffraction, scanning electron microscopy and colour analysis (CIELab method). The results reached suggest the possibility to recover the steel ash both as a starting material in glass and glass-ceramic formulations and as a colouring agent in place of a pure iron oxide into a colourless base system. (C) 2002 Elsevier Science Ltd. All rights reserved.