PHILADELPHIA — “That, to me, looks like Egyptian blue,” Lynn Grant said as she scrutinized a painting on mud plaster from more than 3,100 years ago.

Colleague Molly Gleeson agreed, but was curious why tests showed that the paint contained iron — not a standard ingredient in the ancient blue pigment.

A typical interaction for members of the conservation staff at the University of Pennsylvania Museum of Archaeology and Anthropology — with one exception. They were leaning over their microscope in full view of the public.

The Penn Museum recently opened the new artifact lab in an airy, light-filled space on its third floor, surrounded by a glass wall for easy viewing by museum-goers. Someone is always on duty analyzing, cleaning or mending precious mummies and other Egyptian items from the museum’s collection, and twice a day the conservator opens a window to field questions from anyone who happens by.

Public science is all the rage as museums strive to engage a new generation of visitors. In recent years, the Brooklyn Museum, the Smithsonian’s Lunder Conservation Center in Washington, D.C., and the Museum of Fine Arts Boston all have built conservation labs that are open to public view. Some of the natural history museums have been at it much longer, notably Philadelphia’s Academy of Natural Sciences of Drexel University, with the fossil prep lab that opened in the late 1990s.

In the new lab at Penn, most of the 30 items now on display had been hidden away in storerooms of the museum, which is celebrating its 125th anniversary this year.

Many of the objects in the artifacts lab pose some kind of mystery, and were chosen because scholars were eager to take a closer look, said David P. Silverman, curator in charge of the Penn Museum’s Egyptian section.

“The whole idea was to include not only what we wanted, but also what we knew the public would be interested in seeing,” Silverman said.

With the mud plaster painting, the unknowns include the name of the man depicted, and whether the work is entirely authentic. Unlike most of the more than 40,000 items in the museum’s Egyptian collection, the painting was not excavated by scientists, but was purchased in 1925 from a dealer, so information on its origins is scant.

It depicts a man of the elite class holding an ankh — a cross with a loop that represents life — in his right hand. Silverman has vague misgivings about the work, in part because of the man’s angular form. He thinks perhaps it is authentic, but was touched up or “enhanced” long ago by someone with an inexpert hand.

The atypical iron in the blue paint was revealed with a technique called X-ray fluorescence, said Gleeson, the project conservator. The blue pigment also contained the usual copper.

“I need to do more research into what we should be seeing,” Gleeson said.

Other items lying on tables in the lab include mummies, wrapped and unwrapped, intact and not so intact. Several consist of just the heads, the expressions on their walnut-brown faces frozen in time.

Gleeson said the most popular query from visitors is whether the mummies are real. Sure enough, that question came from a group of home-schooled children who were visiting on a recent weekday.