Modelled masses of carbon, alumina, and silicate dust (coloured square) at present in Cas A compared with the masses derived from Spitzer data by Rho et al. (2008; grey shaded area) and Arendt et al. (2014; green shaded area). The initial dust mass formed by the supernova is given as a dotted coloured line. Dust masses derived for the SNR 1E 0102.2-7219 in the Small Magellanic Cloud from Spitzer data (Sandstrom et al. 2009) are also shown (full back line).