Microcrack leveling describes the ability of silicone sealant, when applied, to spontaneously fill and smooth very fine, hairline cracks in the substrate. This property is related to the consistency and fluidity of the sealant. Silicone with good levelling ability can slightly "flow" into the unevenness and pores of the material, thus creating not only an aesthetically smoother joint, but above all ensuring perfect adhesion and sealing of the joint. Materials without this property could form tiny bridges over micro-cracks, leaving unfilled voids underneath, which could reduce the tightness and durability of the joint. It is therefore the ability of the sealant to form a continuous and fully contacted surface even on substrates that are not perfectly smooth.