Normalised spectra of Haro 6-10 N (top) and Haro 6-10 S (bottom) obtained with TIMMI2 on February and December 2002 and with MIDI on December 2004, with the computed maximum optical depth. A second-order polynomial has been fitted to the data between 8.8 and 10.2 μm (dot-dashed lines) to compute the maximum optical depth (τ). For comparison the ISM silicate profile from Kemper et al. (2004) is overplotted (dashed red lines).