What is GETTER?
Getter is a chemical (usually red phosphorus) which is introduced into a bulb and designed to chemically react with stray oxygen rending stray oxygen harmless.
Using mechanical devices such as vacuum pumps is never 100% successful in removing all oxygen, so getter is introduced to finish the job chemically.
Getter can not remove large amounts of oxygen, so most oxygen does have to be mechanically removed before bulb is sealed.
The filament is usually coated with phosphorus, then after bulb is sealed the filament is electrically energized to high incandescence at which time a blue glow appears in the bulb for a second or two. After which the blue glow disappears and the "clean-up" is associated with a pressure drop (vacuum), and the bulb then is ready for use.
reference for this page: GETTER
reference to this page: INCANDESCENT BULB