PORTLAND — Once the paintings languished in the City Hall attic.

Now two city-owned portraits are returning to life, conserved by a nonprofit with studio space above the State Theater at 142 High St.

“We are trying to be a resource for the state and beyond and have people be aware of the conservation process,” Bonnie Mattozzi of the Maine Project for Fine Art Conservation Project said Monday.

The portraits of U.S. Sen. William Pitt Fessenden and Gov. Percival P. Baxter are the first of 18 Mattozzi and her husband, Domenico Mattozzi, would like to conserve for the city.

To help fund the work, MEAC has organized an appraisal day at the University of New England Gallery from 10 a.m. to 2 p.m. Saturday, Oct. 3. Four appraisers will be on hand to evaluate antiques, art, collectibles and heirlooms. Single items will be appraised for $10, two items for $18 and three for $25.

The Mattozzis estimate it will cost $20,000 to conserve the 22-inch-by-26-inch painting and frame of Fessenden, who also served in the state Legislature and as secretary of the treasury under Abraham Lincoln.

The estimated cost to conserve the 32-inch-by-40-inch portrait of Baxter is more than $12,000. The Mattozzis intend to conserve the paintings, and others, without using taxpayer money.

“It is not as glamorous as the art you see in the museums, but if it is gone, it is gone forever,” Domenico said.

The Mattozzis are careful to stress they and their staff of about six people conserve, not restore, art. This means repairs can be made to the canvas, the accumulations of varnish and dust can be removed, and cracks filled in through painstaking processes.

“You basically try to stop the decay the best you can,” Domenico said. “Everything that is done has to be reversible. In restoration, you can do more damage because you apply things that are not supposed to.”

The couple also work with private collectors and contemporary artists to conserve and suggest ways to ensure paintings will remain in good condition, following guidelines set down by the American Institute for Conservation of Historic and Artistic Works.

The first step is an assessment of the painting and damage done to it, followed by a treatment proposal and then the estimate to do the work.

Fessenden and Baxter had seen better days on canvas when the Mattozzis brought them to the studio two years ago. Most of Fessenden’s face had faded and the Baxter canvas was in shreds.

Conservation work can entail covering a painting with thin layers of Japanese paper while the backing is placed on Belgian linen. Varnish and dust removal is done in small brushstrokes, and paint is used only to fill in cracks and other damage, not to enhance the painting overall. The painting may also be stretched again.

“We use colors that can be removed,” Bonnie said.

The Mattozzis draw from colleges and art schools both near and far for staff and interns, including University of Southern Maine student and Scarborough High School graduate Aileen Andrews, Maine College of Art graduate Melisande Lopez, and Latvian native Katrina Jacques.

Andrews was dabbing lightly at a landscape Monday, adding color with a fine brush.

“It is slow work, but it is extremely rewarding,” she said.

Baxter and Fessenden are now more vibrant, with mostly fill-in painting left in the process, but not quite ready for public display. The progress and process has pleased the Mattozzis.

“These are people who made Portland, Maine, and the country what it is today,” Bonnie said.

David Harry can be reached at 781-3661 ext. 110 or dharry@theforecaster.net. Follow him on Twitter: @DavidHarry8.

The conserved portrait of Gov. Percival Baxter seen Monday at MEAC. The cracks will be filled by small brush strokes of paint.A section of the city-owned portrait of Gov. Percival Baxter before conservation work began at MEAC.A section of the city-owned portrait of Sen. William Pitt Fessenden before conservation work began at MEAC.Bonnie and Domenico Mattozzi show conservation work on a city-owned portrait of William Pitt Fessenden at their High Street studios. The couple would like to conserve as many as 18 paintings for the city.