Liquid Paper
The story goes that Graham began to use white, water-based tempera paint and a thin paintbrush to cover her typing errors, calling her invention Mistake Out. Initially she kept her idea to herself (her boss never noticed the paint on his documents) and did not actually sell a bottle of Mistake Out until 1956.
Ever resourceful, Graham recruited a team to help her perfect her product. Graham eventually patented the product and renamed it Liquid Paper. However, her invention was certainly no overnight success and she continued to work in the bank, managing Liquid Paper after hours.