A device for separating and removing a rigid core when building a tire, including a slide table and positioning means which are provided on a support table of the separationremoval device. The fluorescent is a compound comprising each one of I, III and VI group elements having a chalcopyrite structure, has a particle diameter of 0. The optical source is coupled to the at least one sensor by an optical fiber. A method of forming a friction plate for a clutch is also provided.