Boston’s loudest, most colorful show of the year begins quietly, a few days before the Fourth of July, on a barge in the middle of the Charles River.
Here, workers meticulously lower acorn-shaped firework shells into black mortars, to be launched around 10:30 p.m. Monday at the 43rd annual Boston Pops Fireworks Spectacular.
This year’s fireworks will be more “nuanced” than last year’s, said Ian MacKenzie, chief pyrotechnician at Fireworks by Grucci, which produces the popular display.
“There’ll be highs and lows,” he said. “A lot of contrast.”
Big, loud “salutes” will be coupled with soft, twinkling “willows,” he said.
All told, the fireworks show will cost around $500,000, which includes hiring Grucci, renting the barges, and buying insurance, said Steve MacDonald of Boston 4 Productions, the nonprofit that puts on the event.
This year, however, that money is coming not from a corporate sponsor, but from David Mugar, who has orchestrated the event since its genesis in 1974.
For the first time in years, the event has struggled to find sponsorship, leaving its future in doubt. In his final year at the helm, Mugar decided to pick up the event’s $2 million tab.
“I just couldn’t let people down,” he recently told the Globe.
Mugar will remain on hand as a consultant, MacDonald said. But without him in his official capacity, shows won’t be quite the same.
“There are so many things he was first to do,” MacDonald said.
Preparation for the fireworks is a logistical challenge that begins long before Fourth of July weekend in Grucci’s Virginia and New York factories, MacKenzie said. But after years of practice, the process has become smooth.
“It is a well-oiled machine,” he said.
The only thing he can’t control is the weather.
“We just cross our fingers and hope,” MacKenzie said.
Apart from lightning, strong winds are a fireworks show’s worst enemy, he said. If winds top 20 miles per hour, fireworks are not permitted under state law.
This year’s show will use fireworks up to 10 inches in diameter, which requires a 1,000-foot safety zone around the Charles River barges. That part of the Charles will close around 4 p.m. Monday — boaters won’t be allowed in the safety zone. Fireworks will also be shot from the Massachusetts Avenue Bridge, which will close around the same time Monday.
In his 43rd year as a pyrotechnician with Grucci, Patrick Bosco said he has seen the industry change considerably for the better. It’s much safer, he said, and computerization has turned choreographing a show into an art.
The fuses of each firework are connected, through a labyrinthine arrangement of wires and cables, to computers where technicians sync the blasts with music.
“It’s an artwork,” Bosco said. “It’s not just throwing fireworks into the sky anymore.”
MacKenzie likes to get technical about fireworks, explaining combustion and propulsion to people who ask him about his job. When he delves into the science behind it, he’s used to seeing people’s eyes glaze over, and he often turns to a metaphor.
“It’s a picture we’re trying to paint with the effects,” he’ll say.
MacKenzie was hesitant to disclose too many details about the show to preserve the surprise. And come Monday, there’s a surefire way to know how well they’ve done.
“When we hear oohs and ahs, that’s what does it for us,” Bosco said. “That’s when we know we’ve done our jobs.”Reis Thebault can be reached at email@example.com. Follow him on Twitter at @reisthebault