The invention relates to an uncovering compound for uncovering surfaces of materials with pronounced Si crystals, in particular of cylinder bearing surfaces made from aluminum materials with pronounced Si primary crystals. The uncovering compound according to the invention preferably includes very fine uncovering material, particularly preferably comprising silicon carbide grains with a grain size in the range from 4 μm to 0.1 μm and/or ceramic fibers comprising Al2O3, which is embedded in a visco-elastic plastic carrier compound. The invention also describes a process and a corresponding apparatus in which the uncovering compound according to the invention is used.