Method for introducing a limited amount of mercury into a fluorescent lamp during manufacture thereof includes the steps of forming the lamp with an exhaust tubulation therein open at an end thereof and provided with a ball retention structure, exhausting the interior of the lamp through the tubulation open end, placing a rigid ball of inert material in the tubulation between the ball retention structure and the tubulation open end, the ball having a coating of a selected one of silver, gold, and indium, of a selected mass over a selected surface area of the ball, and mercury on the coated area, and sealing the open end of the tubulation, whereby the amount of mercury retained on the ball and thereby introduced into the lamp is limited by the selected mass of the coating on the ball.