One method empirically determines a stiffness value for each of two or more different subsets of the bristles of a brush seal, then calculates a variation in stiffness, and then identifies the brush seal as defective if the calculated variation in stiffness exceeds a predetermined stiffness variation criteria. One apparatus includes a load transducer having a contact head sized to contact less than twenty percent of the bristles, a displacement transducer which measures the displacement of the free ends of the contacted bristles, and a clamp for securing the brush seal and presenting the bristles for contact.