penetrandi – petrooli materjali ebapidevustesse tungimise ja nende märgamise järgnevalt pinnale kantud valgendkriidi märgumisel põhinev kapillaarkatse (vrd õli-valgendkriitproov), liquid (kerosine) purposely introduced into surface cracks and the brought out again would reveal the locations of these cracks on the surface coated with chalk or suspension of chalk in alcohol; used in testing of railroads (compare: oil and whiting penetrant test)