A serpentine tube used in the manufacture of a fluorescent lamp is coated with a reflective or phosphor material. A magnetic material and coating material slurry is placed within one end of a serpentine glass tube. A magnet is placed adjacent the magnetic material and coating material slurry and is moved in a path conforming to the shape of the serpentine tube. The magnet causes the magnetic material and coating material slurry to travel along therewith, coating a portion of the interior surface of the serpentine tube with a reflective, phosphor, or other material. In another embodiment of the invention, abrasive magnetic material is placed within the serpentine lamp for removing a previously coated material resulting in an aperture being formed. The present invention is particularly suited to the manufacture of serpentine fluorescent lamps that are used to illuminate flat panel displays.