Final answer:
The white paint on the Rosetta Stone was added in 1981 as a protective coating and was removed in 1999 during a conservation project at The British Museum.
Step-by-step explanation:
The white paint that was removed from the Rosetta Stone in 1999 was applied in 1981 as a protective coating. This removal was part of a conservation effort during the 'Cracking Codes' exhibition at The British Museum.
The conservation process involved meticulous cleaning to reveal and preserve the original inscriptions. This included removing substances such as grease from human handling, a coating of carnauba wax from the early 1800s, printer's ink from 1799, and finally the white paint from 1981. A square was left untouched to show the contrast between the treated and untreated surfaces.