The glass tube manufacturer employs 21 members of Local 219 of the Glass, Molders, Pottery, Plastics and Allied Workers Union.
Union shop steward Jill Sanderlin, who ran a picket line outside the Wheaton Avenue facility, blamed a proposal to turn three union inspector positions into salaried non-union positions.
"That's not fair," said Sanderlin, a 17-year-employee. "In essence, it seems they're trying to break the union."
The union's five-year contract expired at the stroke of midnight Monday. Talks got under way Tuesday.
The 42-member labor force is equally divided between union and salaried positions, Sanderlin said. The firm has laid off 180 workers in the last two years.
"The issue is one of economics," said Joe Plumbo, the company's owner and chief executive officer. "And it's one of the fox watching the hen house, of union job watching union job. We compete globally, and we can't have that."
Plumbo, who pitched in with packing work, said he does not expect the strike to end quickly.
"It's an easy choice for me in a sense, because the economy has me against the wall," he said.
Millville resident Frani Alcorn, an inspector for 11 years, said inspectors were asked about the idea but never given guidance as to what would happen to their pay levels.
The hourly base rate for the position is $11.12.
"Once you're out of the union, they don't have to pay you anything," Alcorn said. "We were afraid they'll offer less money. You have to go with your gut."