Left panel: surface concentration of Fe as a function of T_eff in clusters (M 3, M 13 NGC 288) from Behr (2003) with original Fe concentration between  − 2.3 and  − 1.3 dex the solar one. Models are shown for those two metallicities. Each color-coded segment represents the evolution of the surface Fe concentration. The line is solid for the time interval from 10 to 30 Myr after ZAHB, but dotted from 0 to 10 Myr. Right panel: surface concentrations of Fe as a function of T_eff in the cluster NGC 2808 from Pace et al. (2006). The color-coding is defined in footnote (5). For most models the spanned time interval is approximately 30 Myr.