It's dark inside Hawaiian Hall, the gloomy, aging heart of the Bishop Museum.

For the moment, that's probably a good thing. The stuffy, shadow-streaked interior masks a beautiful, but deteriorating Victorian-era structure sorely in need of repairs.

Paint flakes hang off the ceiling in hand-sized chips.

Koa wood trim — on display cases, windows and railings — is faded in some places and oxidized in others, a mottled acne of hardened varnish and more than 100 years of dirt and dust.

Fans bolted onto iron railing grates buzz the air in an anemic attempt to cool a building without air conditioning or any form of climate control so necessary to preserve artifacts. The extension cord from one fan snakes up a cast-iron column to a ceiling outlet.

And some of the original beauty of Hawaiian Hall was muted by attempts to modernize it: Skylights are covered and windows shuttered.

But the Bishop Museum is about to start a $20 million restoration project that will give Hawaiian Hall and several adjacent structures a much-needed facelift. When finished, visitors will have access to more of the museum's beloved artifacts in an environment better suited to long-term preservation.

The project will require the museum to close Hawaiian Hall for about 18 months, beginning tomorrow. Two of the adjacent buildings that make up the Hawaiian Hall Complex — Polynesian Hall and the Vestibule/Picture Gallery — also will be closed at various points. The Kahili Room, however, will not close.

To ease the blow of closing the complex for such a long time, the museum will waive admission today.

It is a job long overdue. Museum staffers consider the Hawaiian Hall Complex, with its distinctive, quarried blocks of volcanic stone, their largest artifact.

"It's still beautiful," said William Brown, president and chief executive officer of the museum. "It's still an extraordinary place. What we are doing is, for the first time in decades — and for the first time ever in terms of some basic things — restoring and improving the whole complex."

The cornerstone of the project will be climate control and new electrical wiring that will replace a system installed in the 1960s, when electricity was first introduced into the complex, Brown said. Only the smaller Polynesian Hall and nearby Kahili Room have air conditioning, installed in 1972.

The change to Hawaiian Hall will cool visitors accustomed to 80-degree temperatures in the summer, but it will come with a $17,000-a-month electric bill.

More importantly, the air conditioning will reduce threats to preservation.

Initially built to use natural ventilation and light, Hawaiian Hall is open to breezes, artifact-eating insects, humidity and the rise and fall of temperatures. Temperatures in display cases can top 80 degrees — not bad if they stay that way, but higher than the preferred constant of 70 degrees, Brown said.

Access will be improved for the 300,000 to 400,000 visitors who tour the museum each year.

For the first time, the complex will have an elevator that will link floors from the three different buildings that went up between 1898 and 1903. It will have to be built outside them in what is now a courtyard in the back because none of the floors in the different buildings are aligned.

The changes will allow the museum to modernize exhibits in Hawaiian Hall that have not been changed in decades. Brown can point to display-case materials that are 30 years old, a gem collection that looks more like a youth science project than a professional museum exhibit, and empty display drawers begging for artifacts.

"Frankly, the exhibits are kind of tired," Brown said. "And they will be everything but tired when they're done."

The current patchwork of displays from different eras will be replaced with a modern interpretive approach and the ability to easily create new exhibits drawn from the museum's 24 million artifacts, Brown said. Hawaiian Hall and Polynesian Hall will be able to display twice as many objects.

"It will be much more inviting," Brown said. "It will be warm and lit in a way that shows the colors. We'll still keep the basic historical feel. I don't think we'll feel old-fashioned in a bad way."

There was talk during the 1980s of remodeling Hawaiian Hall but funding was spent on other tasks. When Brown arrived in September 2001, he knew he had to first finish the $17 million science adventure center despite the desire to tackle the Hawaiian Hall Complex.

The center opened in November, allowing Brown to concentrate on fund-raising for the remodeling. So far, Brown has raised $10 million for the $20 million project — from the Legislature, the Office of Hawaiian Affairs and a variety of foundations. He's confident the public will pony up the rest.

But the museum waited until today to tell anyone except potential donors what is about to happen. Even its 30,000 members have not received official word — that will come in the next membership newsletter.

Clare Hanusz, whose family has had a membership for about a year, wondered what she was going to tell her two young children. The Manoa mother takes them to the museum several times a month, and every visit includes a stop at Hawaiian Hall for a hula performance.

Still, Hanusz understands the museum's need.

"If you look up at the ceiling and if you look at the windows, you can tell that the years have taken their toll on the building," she said. "And it's unfortunate that the facility will need to be closed for so long to make repairs. But I trust they know what they are doing."

Down on the central floor of Hawaiian Hall, where the hula shows entertain longtime residents and tourists alike, the restoration will be done with a dose of caution, given the public's long familiarity with the hall's central features: An authentic thatched hut obtained on Kaua'i in 1902, a model of a heiau made with rocks from Big Island heiau, and an enormous sperm whale skeleton hanging from the ceiling.

All three will remain.

DeSoto Brown, who is not related to the museum president and serves as collections manager for the museum's archives, said they are central icons of a building that represents an era.

"As it is restored, we have to be respectful of its age," DeSoto Brown said. "We have to not alter it from its original appearance. This is not only a renovation, it is a partial restoration, too. We can't arbitrarily — and we don't want to arbitrarily — make drastic changes."

During construction, every item on display will be removed and everything about how the museum tells the story of Hawai'i will be thought through before it goes back on display, DeSoto Brown said.

"Every single case will be re-designed," he said. "It's a huge job we are putting a lot of thought into."

That task is both exciting and daunting, and the possibilities can give Betty Lou Kam, the museum's vice president for cultural resources, a kind of nervous excitement, like someone suddenly able to tell a really good story after years of waiting.

"There are so many expectations for the museum," she said. "Expectations of those on the outside of the museum and those in it. We want it to be the best it can. We want it to be meaningful and we want it to be sensitive. All those things are important."

Kam knows better than most what's at stake.

She can open practically any drawer and box locked away in the museum's special, climate-controlled storage room. She can stare into the shell eyes of a woven war god — one of only 17 left in the world — and ponder its history. She can view braided human hair lei worn by the most powerful of Hawaiians.

But she can't display any of them for the public, can't put them in an antique display case in a building that is "sweltering hot" in the summer, and certainly can't risk putting them in a hall that leaked until a year ago and sprouted mold during the recent March monsoon.

"The objects have to be appreciated," she said. "They have stories to tell. If they are stuck in the storage area, they are not telling their stories to people who are interested. There is something about coming up and seeing something. The encounter motivates you to want to know more about it and why."

Reach Mike Gordon at mgordon@honoluluadvertiser.com.