Differences during the last 15years in materials' composition in Municipal Solid Waste Incineration (MSWI) regarding bottom ash (BA) were assessed as a function of particle size (>16, 8–16, 4–8, 2–4, 1–2 and 0–1mm). After sieving, fractions >2mm were carefully washed in order to separate fine particles adhering to bigger particles. The characterization took into account five types of materials: glass (primary and secondary), ceramics (natural and synthetic), non-ferrous metals, ferrous metals and unburned organic matter. The evaluation was performed through a visual (>2mm) and chemical (0–2mm) classification. Results showed that total weight of glass in the particles over 16mm has decreased with respect to 1999. Moreover, the content of glass (primary and secondary) in BA was estimated to be 60.8wt%, with 26.4wt% corresponding to primary glass in >2mm size fractions. Unlike 1999, in which glass was the predominant material, ceramics are currently the major phase in bottom ash (BA) coarse fractions. As for the metals, respect to 1999, results showed a slight increase in all size fractions. The greatest content (>22wt%) of ferromagnetic was observed for the 2–4mm size fraction while the non-ferrous type was almost non-existent in particles over 16mm, remaining below 10wt% for the rest fractions. In the finest fractions (<2mm), about 60 to 95% of non-ferrous metals corresponded to metallic aluminium. The results from the chemical characterization also indicated that the finest fractions contributed significantly to the total heavy metals content, especially for Pb, Zn, Cu, Mn and Ti. Display omitted •The content of glass in particles >16mm has decreased in weathered bottom ash (WBA).•Entire glass bottles have been easily recycled and extensively substituted by plastic.•There's still a significant amount of glass that's left unrecycled: 60.8%.•Ceramics are currently the major phase in WBA coarse fractions.•The finest fractions are the major contributors to the heavy metals content.