A new experience in trumpet ownership. When you get a valve job done, an abrasive is used to lap the newly larger pistons for the perfect fit in the freshly honed casings. The abrasive consists of tiny crystals of industrial gemstone. Sometimes some of it lodges itself here and there in the trumpet. If after a valve job you suddenly find your valves frozen or nearly so and moving only with force and making a scraping sound, some of the abrasive has entered your valves and a thorough cleaning is need to get rid of it. FYI . . .