After a six-year fundraising campaign, restoration work will soon begin on the 116-year-old rose window from Riverside Presbyterian Church, which was removed from the east wall of the church last week.

For the next four months or so, the circular opening will be covered by plywood. But when the stained-glass window is put back in place late in the fall, it should be strong enough to weather another 100 to 150 years, according to the congregation’s pastor, Rev. Dr. Scott Jansen.

“It will be structurally more stable,” said Jansen. “It will also be a lot cleaner. There’s 120 years of soot being cleaned off, so it’ll look bright and clean.”

Actually, the job includes more than the rose window itself, which depicts the angel Gabriel. It also includes the eight semicircular lobes and eight triangular windows that frame the rose window — 17 windows in all.

Church leaders have been planning the work since 2007, when the stained-glass windows in the church’s bell tower were restored. And they’re not done. Once this effort is complete, fundraising will continue to one day restore the Good Shepherd window and several other narrow lancet windows that illuminate the sanctuary.

In May, the church decided to give the green light to the restoration of the rose window — at a cost of $70,000. Money was raised through memorials, the sale of brick pavers, a capital campaign and a large anonymous donation, which will cover about half the cost, according to Jansen.

The church hired Chicago-based Restoric LLC to lead the restoration effort. That company was onsite June 24 to oversee the removal of the windows, including the rose window, which weighs about 180 pounds and is about 6 feet, 9 inches in diameter.

According to Neal Vogel, principal at Restoric, the rose window is from a separate capital campaign, a bit later than the outside lobes and triangular windows. While those peripheral windows are more ordinary in design, Vogel said the rose window “is an exceptionally well-done piece.”

Vogel said he believes the window may be the work of the New York-based Church Glass and Decorating Company, a rival to Tiffany and Company and a firm that, like Tiffany, also employed a designer named Edward Sperry. The window resembles Sperry’s work, said Vogel.

“Sperry was doing the most exceptional work in Chicago at that time,” said Vogel. “On a scale of 1 to 10, this window is a 9.”

The rose window — which is actually slightly egg-shaped, said Vogel — will be disassembled, cleaned and then reassembled using as much of the original lead as possible. That work will be done by Botti Studio of Architectural Arts in their workshop in LaPorte, Ind.

In addition, the old pine frame will be replaced with a new mahogany frame. It’ll be slightly thicker than the old frame “to meet modern wind loads and codes.” The rose window will not have a protective storm window on the outside. One that was in place for many years, until 2007, was responsible for the deterioration of the pine frame, which was crumbling in some places.

“When we pulled the glass out [on June 24], I was amazed it hadn’t blown out of the opening in a storm,” said Vogel.

In addition to cleaning the glass, part of the restoration will be to reapply Bible verses that had worn off the glass over the decades.

“From the outside, it will look pretty much the same,” said Vogel. “From the inside it’ll look pretty stunning.”