Spotcheck SKL-SP2 Penetrant Spotcheck SKL-SP2 is a solvent removable penetrant offering maximum reliability in the detection of surface-open flaws and discontinuities. Spotcheck SKL-SP2 is a solvent removable ( or post emulsifiable) red color contrast penetrant with outstanding penetrating characteristics. It offers maximum reliability in locating surface-open flaws and discontinuities and has been successfully used on non-porous ceramics and other similar materials.