PURPOSE: To prevent the deterioration of withstand voltage by putting the fine pieces or granules, of an easily electrified member and a magnetized member, in the inner side of a bulb or a bulb structure to be vibrated or rotated, and eliminating an adherent substance sticked on the inner side of the bulb or the structure by the friction of the vibration or rotation.

CONSTITUTION: Fine pieces or granules of an easily electrified member are put in the inner side of a glass-made bulb structure such as a panel and a funnel of a black-and-white picture tube or a color picture tube just arrived. Then the inner surface of the bulb or the structure is rubbed with these fine pieces or granules by vibrating the bulb or the bulb structure or suitably tilting them to be rotated. In this case, a substance, easily electrified of static electricity, having low hardness, and containing no halogenation element such as Cu, F, and Cl, like formal resin and acrylic resin etc., is used as the easily electrified member. One end opening such as the bulb is closed, and then the bulb or the structure is washed with flowing water or hydrofluoric acid water etc., or by a pure-water shower or a supersonic wave.