The koa display cases are all glossy with lacquer and the pillars have been stripped of layers of white paint at the Bishop Museum's Hawaiian Hall, and for a brief period yesterday the sun shone through the windows.

The three-story museum hall has been restored to its past glory, allowing visitors to see the splendor of the 100-year-old architecture. The museum yesterday gave journalists a sneak peek at the nearly completed project, which necessitated opening the windows.

When the artifacts begin returning in March, the natural light from the 67 windows will be replaced by museum-quality indirect lighting as part of the $21 million general museum renovation.

The bulk of the money, $16 million, is being spent on Hawaiian Hall, which is listed on the National Register of Historic Places. Work includes shielding its artifacts from destructive ultraviolet rays. The windows will be covered by wood panels that from the outside look just slightly darkened but from the inside look like paneling.

Bishop Museum closed Hawaiian Hall in June 2006 and will reopen it in August. Hawaiian Hall is in many ways the heart of the museum, with its iconic 50-foot-long sperm whale skeleton suspended from the ceiling and displays of Hawaiian artifacts, including delicate feather capes, woven basketry and polished wooden bowls.

"We tried to keep the windows available to see out of from inside the museum," said John Fullmer, vice president project designer Mason Architects. "But you need to lower the light levels for preservation. We couldn't get the light levels low enough."

The window panels will provide more display space. Touchscreen monitors and video systems will give audiences new ways to access information.

For more than 40 years, the windows were covered by exterior wooden shutters that allowed some light and air to circulate into the building but altered the building's original appearance. Those have been removed, but a skylight — once covered in black plastic — has received a coating that will allow light to come through but block the sun's damaging rays.

The renovation included revarnishing the koa in the building, restoring faux-bronze pillars, installing air conditioning and an elevator, which will allow people with disabilities to see the upper floors.

"When it was first designed, it was lit by natural light," said Betty Lou Kam, Bishop Museum vice president of cultural resources. "We have 200-year-old artifacts that will fade. It would be a loss if a cape or cloak faded."

Hawaiian Hall was built between 1887 and 1903 and was designed by architects C.R. Ripley and C.W. Dickey, Kam said. Initially it was built to house Princess Bernice Pauahi Bishop's personal collections.

"We're trying to restore the hall to what it once was," Kam said. "The work we've done will keep the sense of the building as it was when it was first built."