This cold snap is slowing the plans of muralists Kaitlyn Dine and Aaron Kane. They need another afternoon or two of warm weather to put the final touches on the piece they are painting downtown.

Their paint — normal exterior latex — gels and eventually freezes, playing havoc for the two illustrators. Dine is a master’s degree candidate at New Hampshire Institute of Art, Kane’s a recent graduate. Luckily, only a few details remain, and it would take a half hour of inspection to find a few paint beads, pencil lines or blotchy shade that begs for a final coat.

The mural graces the exterior window of a bar (Penuche’s Ale House). Bar patrons, downtowners and even graffiti artists have been respectful, Dine said.

“The only thing we’ve really had trouble with is paint freezing,” she said.

The mural is symbolic, fun and even includes social commentary. It depicts Manchester’s transformation from a sepia-toned, 19th century milltown into a colorful, high-tech community. The Millie the mill girl statue overshadows one panel. Another feature? A 60s-era sci-fi robot with a taste for alcoholic beverages — kind of like Dean Kamen meets the Shaskeen?

Its near completion coincides with Artist as Citizen, an exhibit that opened Friday night at the Art Institute’s Roger Williams Gallery on Amherst Street. The exhibit focuses on the public art that originates from the institute — mostly local murals, but also theatre playbills, downtown banners and posters designed for fundraising efforts.

“The community does have a big say in public art,” said Patrick McCay, chairman of the institute’s fine arts department. As Manchester grows as an arts city, he gives a word of caution: quality matters.

“You can pollute a city with bad murals very quickly,” McCay warns. “We want to make sure the quality’s there.”

With that in mind, as the Queen City continues to embrace art and art becomes more public, we’ve got to start thinking about it seriously.

• Get out your checkbook. We’re stingy types here in New Hampshire, so of course we don’t want to pay for anything. But when people demand something for free — whether art, music, food (or news) — it’s worth what you pay for it. Dine and Kane are getting paid for their mural, and Intown Manchester also commissions New Hampshire Institute of Art students to create the banners that hang on downtown lampposts.

Pay for something, and you get a professional product, said Ryan O’Rourke, chairman of the institute’s illustration department. Don’t expect a student to work for free; the school teaches its students about marketing and surviving as an artist.

• Trust the artist. Few people commission a public work and tell the artist “do whatever you want.” And someone paying for art gets to come up with a concept and select a design. Having said that, the creative mind doesn’t thrive if the buyer micromanages the product.

“I tell my students ‘Do whatever you’re engaged with, and put it into the project,’” O’Rourke said. “When you put your voice into it, that’s usually where the best work comes from.”

• Enough history already. Sure, the Millyard, downtown and old buildings are cool. I get it. But they’ve outlived their usefulness as an artistic subject. If the city keeps relying on them for subject matter, we’ll become like a senile person who can only talk about the past.

“A lot of murals and public art dedicated themselves to what Manchester was,” said Ed Doyle, a Manchester arts commissioner and Manchester High School Central band teacher. It’s time to focus on the future, he said, noting the city just elected its first female mayor.

Or how about art that has nothing to do with Manchester? One of the largest murals is on the alley behind the Palace Theatre, where students created hornets.

• Not just murals. Sure, murals are nice, but nothing tops sculpture when it comes to public art. I’ve learned that a sculpture is being planned for the little-used Gateway Park on Granite Street just off the highway.

Sculpture doesn’t have to be big. Jyl Ditbrenner, a math-science teacher at St. Casimir School, transforms abandoned public telephones into scenes that could be called street sculptures. She uses paint and objects fashioned out of plaster. The phone near Santoro’s Pizza on Union Street is an Italian restaurant scene; the phone on Elm Street near the SNHU Arena makes for a musician street scene.

“It’s something that can bring a lot of smiles to public places,” Ditbrenner said. Her take on public art: it can’t be profane.

• Nothing lasts forever. The weather can take its toll on murals, but nowadays they’re sealed so they can last for years. But recycling art is a good idea. Museums swap out their collections. And every year Intown Manchester puts up a new set of downtown banners.

McCay was happy to discuss the durability of mural paint, but less certain of longevity when it comes to the shelf life of public acceptance. Five years? Ten years?

“Nothing,” he said, “is forever.”

Mark Hayward’s City Matters appears Saturdays in the New Hampshire Union Leader and UnionLeader.com. He can be reached at mhayward@unionleader.com.