Armed with scaffolding, canvas, and a host of tools, art conservators on Wednesday night will begin the delicate process of removing a panel from Pierre Puvis de Chavannes’s famed mural cycle at the main branch of the Boston Public Library.

The panel, known as “Philosophy,’’ has become dangerously detached from the plaster wall that supports it, and conservators plan to use a novel technique to remove it from the wall before preserving the 120-year-old work of art.

“It’s important that we do it, and we do it soon,’’ said David Leonard, interim president of the BPL. “The alternatives are not good, so proceeding down this path is the best option.’’

Like the rest of the panels in the 1896 mural cycle, “Philosophy,’’ which depicts two robed Athenians in the midst of conversation, was painted on linen canvas and attached to the plaster wall using a strong adhesive, a technique known as “marouflage.’’ But while the other murals in the cycle remain intact, “Philosophy’’ is attached to a wall that houses an elevator and ventilation shaft. Conservators believe that over the years moisture from the wall has caused the canvas to detach from the plaster.

“It’s not just that the canvas is coming off, but the plaster is slowly bulging out,’’ said Gianfranco Pocobene, head of conservation at the Isabella Stewart Gardner Museum who is leading the mural conservation effort for the library. “If we sat there and waited another year or two, it could be something catastrophic.’’

Pocobene, who will be working on the mural with his former teacher, Ian Hodkinson, said the canvas was already 75 to 80 percent detached from the wall. He added that the canvas has been temporarily secured with a pair of wood braces. “So yes: it’s urgent,’’ he said.

To complicate matters, Pocobene said, conservators could not simply chisel the rest of the canvas away from the plaster with micro-spatulas.

“After 100 years, that paint structure is very brittle,’’ he said. “When you start inserting tools between the canvas and the plaster, the one thing that’s going to give is the canvas, and that’s where there’s the potential for damage.’’

Instead, Pocobene and Hodkinson developed a technique to remove the canvas from the rear side, taking a portion of the supporting plaster along the way. Working up from the bottom, they plan to pull the mural and a layer of plaster away from the wall, giving them greater access to the mural’s reverse side as they move their way up.

“The whole system is held together by an interlocking rigid panel support system,’’ said Pocobene, who added they would protect the front of the mural with a temporary layer of paper tissue and canvas. “You keep inserting these panels and locking them together, so everything you’ve detached becomes stretched and mounted over a rigid support on the front. You don’t want this thing flopping around as you’re working.’’

That’s the theory, but the technique has yet to be employed on an actual artwork.

“We’ve been doing a lot of mock-up trials,’’ Pocobene said, adding that the entire process could take up to three weeks. “We’ve even put together a quarter-scale mockup of the whole structure of plaster and canvas and how you could detach this.’’

Once the panel is completely detached from the wall, art handlers will move it to the BPL’s Cheverus Room on the third floor. Conservators will restore the panel and mount it on a thin honeycomb support, before reinstalling it in its traditional niche.

Malcolm Gay can be reached at malcolm.gay@globe.com.