Maximum velocity (top), kinetic energy (middle), and Lorentz factor (bottom) of accelerated silicate grains, with the grain size increasing from thin to thick. The dashed red curve in the top panel shows the evolution of the shock velocity. In the bottom panel, the dashed blue and dotted green lines correspond to the maximum Lorentz factor obtained with the escape condition (Eq. (20)) and with the loss condition (Eq. (13)), respectively.