Fractional destruction for (left) silicate and (right) carbonaceous grains in C shocks propagating in a cloud of preshock density 10⁴ cm^-3 (top) and 10⁵ cm^-3 (bottom). In the 10⁵ cm^-3 case, the dashed line represents the destruction by sputtering when grain-grain processing, i.e. shattering and vaporisation, is ignored. The intensity of the preshock magnetic field is scaled to obtain critical shocks (see Sect. 2.1 and Table 1).