"I only get dressed once a day," she explains.
Last week, for example, Dillon dressed as a "successful, middling sort of Chester County farm wife" for a midmorning meeting at the 1696 Thomas Massey House in Broomall, where she tends the kitchen garden and does her programs.
By the time she arrived, she'd already been to Bryn Mawr Trust to do some banking. Later, she planned to "clip the ivy that's trying to eat the sidewalk" in front of her house in Haverford.
That means what the bank tellers saw that morning, and what her neighbors would see in the afternoon, was the same century-busting outfit she wore to the Massey House. And why not? It's comfortable.
But don't call it a costume.
"Wonder Woman wears a costume," Dillon sniffs.
She wears "period clothing," made of linen and hand-sewn by herself. It consists of another of those teenage angst-inducing white caps, a well-worn apron - "I carry wood and plants in this" - two ankle-length petticoats, and a "short gown" worn over and pinned to a shift.
On top, underneath the other layers, she's held together by "work stays" that - unlike their criminally tight cousin, the corset - provided welcome back support.
And no, she's not uncomfortable. "I'm not as hot as people wearing polyester underwear," she says.
Dillon is a historian, a retired elementary schoolteacher (31 years), and an author. She has a political science degree from Bryn Mawr College, and a master's and a doctorate in American history from the University of Chicago and Bryn Mawr, respectively.
Her dissertation was about, what else, 18th-century kitchen gardens in Southeastern Pennsylvania, an interest sparked when she arrived at Bryn Mawr from her hometown of Chicago.
"There was Valley Forge. There was Brandywine. There was this sort of thing everywhere," says Dillon, who is drawn to colonial history for other reasons, too.
She loves the smell of wood smoke. She enjoys blacksmithing, sewing, and cooking, "following clues and looking things up. It's like being a teacher, very addictive," she says.
Dillon fits right in at the Massey House, one of the oldest English Quaker homes in Pennsylvania - and in the garden, where she tills the soil with grubbing hoe and wooden shovel and tends an unruly collection of plants with culinary, medicinal, and household uses. They include Rosa gallica and rue, black currants and root vegetables like Gilfeather turnips, skirret, viper's grass, and lemon balm, whose leaves were made into tea that Dillon says was "good for tired brains."
"A lot of a colonial woman's life revolved around the kitchen garden. She was responsible for the health and maintenance of her family, so you need to know what she does all day to see the whole picture."
Not everyone, as Dillon phrases it, "gets what I do."
Kathleen Wall does. As colonial foodways culinarian at Plimoth Plantation in Plymouth, Mass., where the pilgrims first arrived in the new world, she calls Dillon "a huge influence" on her career.
The two met in 1989 in Indiana, at a conference of the Association for Living History, Farm and Agricultural Museums. At the time, Wall was a costumed interpreter at Plimoth.
"Clarissa struck up a conversation about gardens. I was just bowled over," Wall recalls. Dillon drilled her with questions about research topics and sources, then insisted Wall come to a meeting of the group's foodways committee, which studies history through eating habits and culinary practices.
"I went in and there were all these people and Clarissa was in the thick of it," says Wall, who went on to pursue a foodways career at Plimoth.
Then there was the young guy - "teenagers and young men are the worst," Dillon says - who, upon seeing her in full dress in a restaurant where she was headed to a meeting - shouted out derisively, "You're Betsy Ross!"
She answered him with characteristic zing: "No. And Betsy Ross didn't make the first flag. And that's not her real house. And I never 'do' anybody else. I'm me. I am always me."
"Clarissa is awesome," says Pat Martin, Massey board president, who, in period clothing herself, cooks colonial dinners for guests twice a year at the house.
"It was hard living back then," she says. "You think things just grow out there" in the garden, "but wow, then Clarissa shows you that they had to do this, they had to have a nice garden to have enough food for the winter.
"It gets you out of your century, into another world," Martin says, "but look at today's world and sometimes you think it might be better to go back."
Which is a fair question for Dillon, whose turnip wine and "sweet cyder," quince pudding, beer vinegar, and mutton pie would give any 18th-century housewife a run for her money. So we ask: If you could, would you go back?
Surprise: "Absolutely not.
"I wouldn't be able to own property or vote," Dillon says. "I wouldn't be able to do what I want. And you know what they say ...
"A man may work from sun to sun, but woman's work is never done."
For anyone interested in learning more about 18th-century "domestic arts," here are some options to consider:
Sept. 25. Clarissa Dillon presents "The Sincerest Form of Flattery," a look at how the 18th-century English enjoyed various foods from around the world but didn't have the ingredients to make them at home. Their solution was to create imitations using homegrown ingredients. (For example, they pickled nasturtium seeds to stand in for capers.)
The program will be held at 7:30 p.m. at the Marple Christian Church next door to the 1696 Thomas Massey House, at Lawrence Road and Springhouse Road. Free; donations encouraged.
Oct. 20. Harvest Day Festival, colonial crafts and activities, 10 a.m. to 4 p.m., at the Massey House. Dillon will be in the kitchen garden. Free; donations encouraged. Information: 610-353-3644 or www.thomasmasseyhouse.org.
Oct. 27. Cooking class with Dillon, 9:30 a.m. to 2:30 p.m. at the Massey House, $35. To register, call 610-642-4269.
Historian Clarissa Dillon describes the roses in the colonial-style kitchen garden at the 1696 Thomas Massey house in Broomall. www.philly.com/ginny.
Contact Virginia A. Smith at 215-854-5720 or email@example.com.