Working in complete solitude, without even an assistant to grind and mix his colors, in the 16th century Michelangelo painted a work that appeared divinely inspired.

No wonder, then, that the plan to restore the Sistine Chapel has touched off a dramatic controversy and been fueled by anxieties over the possibility of damaging such a masterpiece. But despite the controversy, the world was riveted by one of the most exciting of these discoveries, the unveiling of vibrant color beneath 478 years of pollution, caused by overpainting by restorers of the past and even animal glues. It shocked many who were accustomed to muted tones and somber shades of gray vaulting the ceiling of the Sistine.

To keep further updated on the project, Walter Persegati, Secretary General of the Vatican Museums, will show the process of the restoration in a slide-illustrated lecture, allowing the audience a look at how the fresco must have appeared when Michelangelo first painted it.

The lecture, sponsored by the Smithsonian Resident Associate program, will take place Thursday at 8 p.m. in the Baird auditorium in the National Museum of Natural History. Tickets cost $7 for members and $8.50 for nonmembers. For more information call 357-3030.