What does Scouring mean?
An industrial process where dirt or starch (i.e. oil, grease, sizing) is removed from fabrics.
Style Terms explains Scouring
After has been manufactured, it must be scoured to remove any grease, dust, and grime picked up during production. Scouring most often involves dipping into baths of caustic soda ash.
This is an important step in that it ensures a will fully and evenly take dye.