WD-40
WD-40 is a multi-purpose solution used for rust and corrosion protection, moisture displacement as a penetrating oil, and for cleaning. It is manufactured by the WD-40 Company in the United States. The "WD" in the name stands for Water Displacement, which helps to prevent rust in parts it's applied to.
Cleaning
WD-40 is often found in old typewriters, particularly American makes, due to its ubiquitous nature in the United States, where it is often used for lubrication. Used in typewriters, it may cause typebars to gum up and become immovable. It is often the cause of the ubiquitous typewriter symptom "[sticky keys]]".
WD-40 is often frowned upon in typewriter repair because of its paraffin-wax content. When left on a typewriter for a prolonged period of time, particularly in tight spaces like the segment, WD-40 will attract dirt, dust, and grime before becoming a sticky solid.
Use
WD-40 can be used to dissolve and remove old WD-40 before flushing with another solvent like mineral spirits or lacquer thinner. WD-40 is often used to clean crinkle paint and metal parts when applied with a rag or gentle brush.
