ST. PAUL — The exhibit “Lost Egypt” has returned to the Science Museum of Minnesota, and this time, visitors can actually see it. The last time it was here, it was being built behind closed doors in the museum fabrication shop.

“Lost Egypt” highlights a part of the museum invisible to the public: exhibit design and development. The museum’s exhibit services division employs more than 100 people, ranging from writers to model builders to carpenters and audio-visual specialists.

“We’re one of the biggest players nationally in making exhibits,” said Paul Martin, senior vice president of science learning. “And we have one of the oldest and most prolific touring exhibition programs in the museum field.”

The museum created its first traveling exhibit, on wolves, in 1982. It toured for 10 years before settling at the International Wolf Center in Ely. Since then, the museum has produced 25 touring exhibits. Five currently are on tour, including a large one that explores race and a small one about infectious-disease detectives.

The museum also is one of only a few in the country that regularly build permanent exhibits for other museums. Contract and touring revenue combined brought in more than $7 million in 2011, a figure that has steadily increased and which accounted for about a fifth of the museum’s overall $36 million budget last year.

When the Science Museum was gearing up to move into its new building in St. Paul overlooking the Mississippi River in 1999, Martin and other staff noticed an unsettling pattern. A number of other science centers were being built around the country at the same time. They would hire a lot of exhibit developers to fill the empty exhibition halls, and then those people would be let go when the museums were up and running.

“We had staffed up for this building,” Martin said. “And we knew when we opened, we’d have more staff than we could use here. So in the mid-1990s, we started to look for work with other organizations.”

Martin’s staff made exhibits for the Lemelson Center at the Smithsonian and the California Science Center in Los Angeles, creating a business and building their own expertise at the same time they constructed, say, magnetic racetracks and tidepool displays for other institutions.

The most recent big project was a four-year, multimillion-dollar contract with the Perot Museum of Nature and Science, slated to open in December in Dallas.

“We were building a museum from scratch, and we were looking for the experts to help us,” said Perot’s chief executive, Nicole Small, who is heading up the new $185 million center. “Minnesota kept coming up and coming up and coming up in conversation. I’d say the Exploratorium (in San Francisco) and Minnesota are two of the finest in building hands-on exhibitions.”

Dallas also is working with two private exhibit-design firms, but Small said Minnesota offered the advantage of being able to test exhibits on visitors.

“We love the fact that they had an existing museum and could prototype exhibits on their museum floor,” she said.

The Science Museum of Minnesota designed and built exhibits to fill four galleries. Most of the displays have shipped out, but a few last pieces were being finished last week in the museum shop, which takes up nearly the entire bottom floor of the museum.

Mark Hegnauer was attaching a top to a black kiosk that will sit in the Dallas museum’s sports gallery in a display that will let people “race” against various animals. Like many exhibit builders, he has a background in theater. In his case, he was a prop manager at the Guthrie Theater. Cliff Athorn, director of exhibit production, is a former production manager for the Minnesota Opera.

Nearby stood a prototype of an interactive display about toilets in space for “Journey to Space,” which will premiere in St. Paul in 2014 before touring. The museum got a grant from NASA to work on it with the California Science Center, which just acquired the retired space shuttle Endeavour.

Across the room under a wall of neatly shelved lumber were displays of what looked like fat hockey pucks connected by wood rods for a small exhibit on nanotechnology. The Science Museum will be building 70 replicas of the exhibit to send across the country, paid for by the National Science Foundation, which is eager to raise public awareness about a field it has given substantial funding to in the past decade.

“That’s never been done before,” Martin said, “where there have been that many small exhibits distributed to so many museums.”

The next big thing on the horizon is “Maya Worlds,” an exhibit about the ancient city-states of Mexico and Central America. It will open in St. Paul in 2013 and then go on tour — becoming the museum’s largest touring exhibit to date, on the scale of some touring exhibits developed by for-profit companies, such as “Real Pirates,” which just closed in Minnesota.

The Science Museum came up with the Maya idea and approached the Denver Museum of Nature and Science, which has Mayan artifacts in its collection. Museums in San Diego and Boston also joined the partnership.

“The opportunity came here to us, and coming from Minnesota, I didn’t have to question the source,” said Larry Ralph, director of education enterprises and temporary exhibits at the Museum of Science in Boston. “It looked like it could be a big one, it looked like — we don’t like to use the word ‘blockbuster,’ but this is clearly a topic that we know will interest our members.”

A scale model of the Mayan exhibit, made with foam core walls, was spread over a table in an upstairs design office last week.

“We work a lot with computer models,” Martin said. “But there is nothing like a physical model. It’s so much easier.”

As if to prove the point, someone had been fussing with the “Death and Rebirth” room, rearranging miniature Mayan temple reproductions and display cases like someone moving furniture in a dollhouse.

With so much happening, “Lost Egypt” feels like, well, a previous lifetime to the museum staff. The exhibit was the result of something called the Science Museum Exhibit Collaborative. The Science Museum of Minnesota is a founding member.

Each museum produces an exhibit with input from the group, ensuring top-quality shows that everyone is interested in booking. Titles would be familiar to regular museum visitors. The Museum of Science in Boston developed “Star Wars.” The Fort Worth Museum of Science and History offered up “CSI: The Experience.” The California Science Center did “Goosebumps: The Science of Fear.” And the Science Museum of Minnesota created “Robots and Us.”

The Center of Science and Industry in Columbus, Ohio, had a great idea for an exhibit on ancient Egypt but didn’t have the staff to create it, so it turned to the Science Museum of Minnesota.

“They had more production capabilities for building and designing than we had,” said John Shaw, director of experience production at Columbus. “It was a no-brainer decision for us.”

About 20 people at the Science Museum of Minnesota worked on “Lost Egypt” in 2008 and 2009, from writing the text to building vitrines for some 60 artifacts, including a mummy, as well as scarabs, amulets and pottery. Staff also dreamed up interactive displays to help visitors imagine both life in ancient Egypt and the work of modern archaeologists.

“One of the big ideas was how did people actually build the pyramids?” said Mark Dahlager, director of exhibit design and development. Egyptologists believe the pyramid builders moved the massive blocks of stone on lubricated wood skids. “We wanted people to experience this somehow. We didn’t just want them to read about it.”

Dahlager’s team came up with an exhibit that lets people pull small replicas of pyramid blocks, one on a skid and one without skids. It’s a simple and elegant experiment that took months to refine and test on museum visitors here.

Just as important, the team came up with practical and safe solutions for breaking the exhibit down quickly and moving it.

“Transporting a mummy is something everyone is very nervous about,” Dahlager said.

During the past couple of weeks as the exhibit has been installed, members of the exhibition staff have been slipping away from their cubicles to check it out.

“It’s really exciting for people to see what they worked on,” said Dahlager, “finally all set up in one place.”