The instantaneous sublimation (phase change from solid to gas) of the CO2 grain upon impact absorbs most of the heat from the very thin top layer of the surface coating or pollutant. Maximum heat is absorbed due to latent heat of sublimation.
The very rapid transfer of heat from the top layer of the coating into the grains creates an extremely large temperature difference between successive micro-layers within the coating. This steep thermal gradient produces localized high shear stress between the micro-layers. The shear stresses produced also depend on the thermal conductivity and thermal expansion/contraction coefficient of the coating, as well as the thermal mass of the underlying substrate. High shear generated over a short period of time causes rapid interlayer microcrack propagation, leading to contamination and/or ultimate bond failure of the coating to the substrate surface.