In their hard hats and safety goggles, blue jeans and sweatshirts, they work around the clock making a product that surrounds people every day, yet one that most see right through -- glass.

The employees at Guardian Industries, midway between Selma and Kingsburg, buzz around on fork lifts, operate computers that keep the plant's equipment running, and sometimes work only feet away from a blast furnace that burns at more than 3,000 degrees.

They produce, measure and cut massive slabs of glass, preparing them to be shipped around the country in packs that weigh close to two tons.

For the first time in 18 years, the production line at Guardian Industries shut down on Sunday, allowing for an $80 million dollar expansion project to get underway.

The repairs and expansion will be beneficial not only to Guardian's production, but to local residents as well. Guardian Industries, the 50-acre, 1-million-square-foot plant located just off of Golden State Highway, is investing $10 million on new equipment that will reduce current emissions by 50 percent.

The plant is converting from fuel oil to natural gas for its power and once the 135-day project is complete, the end result will be the most environmentally friendly glass plant in North America.

"In the future, we'll produce a lot more glass, but have half the emissions," said engineering manager Marty Bergman.

Guardian's biggest single market is residential windows, but they also make glass for high-rise buildings, mirrors, furniture and picture frames. The glass is sold as far south as Mexico and as far north as British Columbia and Alaska.

Bergman compares the glass making process to baking.

"We make glass just like making cookies, but with raw materials," he said.

The raw materials that eventually become crystal clear glass start out as sand, dolomite, soda ash, salt cake, charcoal, rouge, limestone, EP dust, and cullet, or recycled scrap glass. After being precisely measured, the materials are transported from the large silos where they are stored into a blast furnace.

At a temperature that can exceed 3,000 degrees, the furnace heats the mixture into molten glass. The glass emerges from the furnace in large sheets, which are then cooled and cut.

When the decision was made to retrofit Guardian's massive furnace, the Environmental Protection Agency mandated that the best available technology be used. Because of California's strict pollution control laws, general manager Don Tullman said that moving the plant to another state was considered.

The $80 million being invested into repairing the plant, which was built in 1978, is not far from the cost of building a new one.

But Tullman said that because Los Angeles is the compnay's biggest market, it didn't make sense to move, in spite of the projection that the new equipment will cost a couple hundred thousand dollars a year to operate.

One of the biggest considerations was the plant's local workforce of 300 employees, made up largely of Selma and Kingsburg residents.

"We've got a great work team here, and most of them wouldn't have moved," Tullman said.

The plant that prides itself on its impeccable safety record, a history free of layoffs and its contribution to the community and local economy.

Within the next few months, Guardian will be annexed into the City of Kingsburg, bringing with it tax revenue that will provide a big boost to the community.

The local plant was the second one built by Guardian Industries. In the past 30 years, Guardian has grown to a company of 60 plants worldwide, 26 of which are float plants -- large plants like the one in Kingsburg where raw glass is made. The company does $6.5 billion in worldwide sales annually, and has plants on every continent but Australia.

In August, the Kingsburg plant was recognized for their outstanding safety record. A huge banner hangs in the plant, stating: "Congratulations Kingsburg -- 4,000,000 hours without a lost time injury."

Because the plant's employees work around a furnace heated to over 3,000 degrees and sharp glass, management makes safety a top priority.

"The number one value here is safety. We're constantly reviewing our processes and our equipment," Bergman said. "Every meeting in this plant always starts with safety."

Th company's commitment has paid off, as their employees will soon be receiving a bonus of about $700 to reward them for their efforts. And last fall, after the four-million hour mark was reached, all employees and their families were treated to a day at Magic Mountain and a night in a hotel.

Once the safety portion of management's daily meetings is completed, they move on to the next order of business -- employee birthday and their company anniversaries. Tullman said that he wants the meetings to be first and foremost about his employees. Issues of production and revenue take a back seat to staff.

"It's a hard place to work, but it's a good place to work," Tullman said.

As Bergman made his way through the various departments of the massive plant Thursday afternoon, he greeted every employee he saw with a smile and a wave. Many shook his hand. Both Bergman and Tullman agreed that they try to maintain a level playing field between the management level and plant employees.

"We're just regular people," Tullman said. "We're blue jeans guys, and that's the image we like to have, frankly."

Of the company's 300 employees, 95 had perfect attendance in 2007.

"We stress attendance, but we reward it," Tullman said. "It's very important for us not to be short on the line."

And before Sunday, that line had not stopped running since April of 1990. The line runs 24 hours a day, seven days a week, 365 days a year -- a schedule that would be daunting for even the most committed employee. Management is always on call, and it's not unusual for them to be called in on holidays. Tullman shared the story of Carlos, an employee who has missed only four hours of work in the past 29 years, and even then, he left only because his father was dying.

In preparation for the major renovation project that got underway this week, between 200 and 300 contractors and over 60 truckloads of steel were brought in, and the old furnace was drained of 1,600 tons of molten glass. The employees that normally work on the line will not be out of work during the 135-day project -- they will be paired with contractors to work on the restoration.

"They're all going to work," Tullman said. "We don't lay off a soul."

Bergman said that the new technology they will be utilizing at the plant will hold Guardian's competitors to a new standard in the future.

"We've literally searched the world for this (technology)," he said.

Guardian welcomes people to call and schedule a tour of the plant to observe first-hand the process of making glass.