The odor of linseed oil and turpentine wafted up the eastern side of the Raynham Hall Museum in Oyster Bay as workers prepared newly bare wood panels for painting.

“It’s rewarding to feel that you’ve preserved more life into a structure,” said Tim Lee, whose Cold Spring Harbor company, TML Builders Inc., is performing the $200,000 exterior restoration on an addition to the nearly 300-year-old home once owned by the Townsend family, who were merchants and patriots during the Revolution.

What Lee calls the restoration of the “exterior envelope,” which includes not just the wood panels but the doors, windows, molding, shutters and other features, is the first phase of work this year on Raynham Hall, which is owned by Oyster Bay Town.

The next phase is expected to begin in July: a $600,000 renovation of the education building, which sits on the western edge of the property.

The nonprofit Friends of Raynham Hall, which operates the museum, is trying to raise $300,000 for a final phase that would restore about one third of the house that is not currently open to the public.

The Victorian-style addition that Lee worked on one day last week was added in the 1800s to the home, whose original structure dates to 1738, when it was purchased by Samuel Townsend, an Oyster Bay merchant and ship owner.

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Since the beginning of the month, workmen have been using heat guns and both machine sanders and hand sanding to remove the layers of paint on this section of the house before applying the oil and turpentine mixture.

“It’s a way to nourish the wood and give it suction so then when you put on primer the wood has actual pores that will marry with the primer,” Lee explained.

After the primer, Lee and his workmen will apply a modern acrylic paint, but one that matches the original gray color of the building as determined by a microanalysis of scrapings of the original paint, museum officials said.

The reason for the acrylic paint, said John Collins, president of the museum’s board of trustees, is because it’s more elastic and doesn’t peel or change color like oil paint does.

Finding the original color of the paint allows them to undo choices made over time that weren’t historically accurate, said Harriet Clark, executive director of the museum.

“If you have a benchmark that you can start from you have a much better chance having something that is authentic,” Clark said.

The attention to detail in the restoration, which includes installing windows that aren’t perfectly flat like modern ones, and crafting specialized tools to repair and replace original details on the building, are steps done to help visitors experience the building’s remarkable history.

“It’s about transporting people to a different time,” Clark said. “Our community is committed to historic preservation and we want to be the best example of that.”

The restoration will also repair and replace shutters and other historic features that had deteriorated over the years.

“When people come to a museum, it’s implied they’re going to see the real thing, not a reproduction, Collins said. “You want to preserve as much original material as possible.”