After spending the better part of a decade restoring the historic Edgartown landmark, muralist Margot Datz considers the Old Whaling Church to be her second home.

“We were living in the scaffolds like we were living in the trees,” she said.

The project began in 2013, when Ms. Datz first started restoring the back wall mural. She had only a grainy photograph from 1865 to base her work on, the last evidence of the original mural by Carl Wendte that had disappeared over 180 years ago.

Together with Chris Scott, executive director of the Vineyard Preservation Trust at the time, the pair traveled to two other “sister churches,” that Mr. Wendte had helped design to gain further inspiration: the Unitarian Church in Provincetown and Nantucket’s Old South Church.

Unveiling will take place this weekend at Minnesingers' concerts. — Ray Ewing

The Old Whaling church itself held few clues to its storied past, but over time Ms. Datz grew to know the space intimately.

“I did find tiny chips of paint that perfectly matched what we had, which was very affirming,” Ms. Datz said.

After finishing work on the main mural in March of 2013, Ms. Datz focused on the recess panels and the vestibule, officially completing that restoration in early December of this year. To achieve the level of depth necessary for a trompe l’oeil illusion, Ms. Datz lined up dozens of individual stripes in alternating shades, creating a plasterwork effect with only paint.

“In the 1840s, this was one of the wealthiest towns in the country, and this church was a grand statement” she said. “But it was also a remarkably modern era, and it was a distinctly modern idea to replace expensive marble and plasterwork with this technique . . . in just paint in one tone there was transcendence.”

The Old Whaling Church was first built in 1843, designed by Fredrick Baylies, Jr. as a place of worship for Edgartown’s Methodist whaling captains. Over time, as the whaling industry floundered and the Island moved to a subsistence farming and fishing-based community, the church fell into disrepair, Ms. Datz said, noting evidence that the ceiling had even caved in at one point and been repaired with tin reinforcements.

In 1980, the Vineyard Preservation Trust acquired the property, and in 2012 put out its ambitious restoration project to bid, ultimately awarding Ms. Datz the project for her prodigious research skills, current executive director Nevette Previd said.

The Old Whaling Church was first built in 1843. — Ray Ewing

Ms. Previd also noted that the updated church is more elaborate in some parts than they were in the original design, especially in the vestibule where guests first walk in.

“The walls were originally supposed to be gray to keep the focus on God,” Ms. Previd said. “But it’s evolved since . . . really, it’s a community building, and this [update] makes it that much more welcoming.”

The final stretch also required additional funding, which Ms. Datz secured herself through a donation from the Kathryn Goodman Foundation.

“I was just a steward of Margot,” Ms. Previd said. “She drove the whole thing.”

The Herculean task of restoring an entire Greek revival church did not come without its trials. The base layers of the walls had been coated in an oil-based paint that didn’t lend itself to being painted over, causing Ms. Datz to experiment with primers and sanding until she found something that stuck. The work was also physically demanding, a challenge the nearly 70-year-old artist did not take lightly.

Behold! — Ray Ewing

“They didn’t think a 60-year-old woman could pull it off,” she said. “It’s a feat of strength and endurance . . . I started doing hot yoga, I could do push-ups on the tips of my fingers . . . I was a tigress.”

Ms. Datz’s daughter, Scarlet Blair, assisted her with much of the project, to the point where Ms. Datz’s granddaughter Georgette set up shop in the halls of the church, playing with dolls and practicing on the piano while her mother and grandmother worked. The scaffolds she painted on were four tiers high, she said, and to thread through them she often had to slide on the seat of her pants.

“I made rubber pants out of garbage bags,” Ms. Datz said, to avoid splinters.

The two women worked in the deep of winter to avoid the tourist season, painting through rain and snowstorms late into the night and sometimes early morning. If it looked like they were going to be snowed in, Ms. Datz said she would prepare a pot roast in the parish kitchen.

“We would call sleeping in the scaffold the king’s nap,” she said with a laugh.

The Old Whaling Church will hold its first event with the finished murals on Friday, Dec. 9 with a performance by the Minnesingers, the Martha’s Vineyard Regional High School choral group.

Although she’s relieved to be finished, Ms. Datz said that neither she nor her daughter or granddaughter will ever truly say goodbye to the place they have left a lasting mark on.

“I loved these walls,” she said. “I’ve touched every square inch of them...Every time we touch, we imbue our environment with love. And even though this isn’t my technique, it’s a very logical thing, it was executed with great care and with great love.”