Patent ID: 6905385

Claim:
A method for introducing a limited amount of liquid mercury into an envelope of fluorescent lamp during manufacture of the lamp, the method comprising the steps of: forming the fluorescent lamp with an exhaust tubulation therein, the exhaust tubulation being open at an end thereof and being provided with a ball retention structure proximate the open end; exhausting the interior of the lamp envelope through the exhaust tubulation open end; placing a rigid ball of inert material in the exhaust tubulation between the ball retention structure and the exhaust tubulation open end, the ball having a coating of a metal comprising a selected one of silver, gold, and indium, and alloys thereof, of a selected mass over a selected surface area of the ball, and having mercury on the coated area of the ball, such that a limited amount of the mercury is retained by the metal coating; and sealing the open end of the exhaust tubulation; whereby the amount of mercury retained on the ball and thereby introduced into the lamp is limited by the selected mass of the metal coating on the ball.