Upper panel: temperature profiles of the neutral fluid for a shock with n_H   =   10⁵ cm^-3, V_s = 30 km s^-1 and b = 1.5 corresponding to Paper III (in blue) and our current model (in red). Lower panel: evolution of the total grain cross section, ⟨ nσ ⟩, for the same shock models, with and without taking into account the grain mantles and normalized to the preshock values of ⟨ nσ ⟩.