Long Island is home to one of the most prominent architectural glass industries in the country, encompassing huge state-of-the-art computerized glass-cutting factories servicing skyscrapers and small businesses that replace kitchen windows.

It’s an industry that uses new technology to give glass properties such as greater insulation, or the ability to instantly switch between clarity and opacity. It also relies on demanding physical labor that poses risks of severe injury from gigantic sharp sheets of glass.

Demand for architectural glass is rising as construction grows. But the recession reduced the number of companies making the glass used by the industry as its raw material, leading to price increases.

And now the local industry faces the challenge of a new competitor: In April, WHTB Glass, a Beijing-based company that bills itself as the largest fabricator of architectural glass in China, closed on the purchase of vacant land in Shirley where it plans to build an $18.9 million fabrication and distribution facility, its first U.S. location.

According to estimates by USGlass magazine, an industry trade publication, the Island is home to at least 392 glass fabricators — companies that layer and cut glass to size — and contract glaziers — companies that install glass as construction subcontractors.

“The first major reason why Long Island is such an important region is access to the quality fabricators that are there,” said Debra Levy, publisher of USGlass, based in Stafford, Va. “Long Island is really dotted with a lot of quality glass fabricators and glass installers.”

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Long Island glass companies have estimated combined annual revenues of $700 million, Levy said, and employ about 19,500. “Many times Long Island firms are the first ones that get to fabricate and install glass in applications that haven’t been used before,” she said.

The Island’s prominence in the architectural glass industry is tied to its proximity to New York City. The region has a large, dense population, and a steady flow of commercial and residential construction.

Long Island has its own trade group and has hosted Glass Expo Northeast, a biennial trade show, for nearly 20 years.

“The architectural glazing industry is feeding a lot of families in the Long Island area,” said Gary Buonavita, vice president of the Long Island Glass Association, the local trade group, and New Jersey sales manager for Solar Seal of Connecticut, a glass fabricator.

Architectural glass — defined as any glass made by melting sand into ribbons of raw glass that float on top of molten tin in large manufacturing tanks — is used as an exterior or interior building material. It is a $42 billion industry in the United States, according to USGlass.

The local industry got its start in the late 1940s as glass shops were founded or relocated from the city to service the growing residential real estate sector, Levy said. It grew as developers began building industrial and office properties here in the ’60s and into the ’70s.

Industry experts said Long Island’s largest glass firm is Oldcastle BuildingEnvelope of Hauppauge, which is owned by Irish construction materials giant CRH plc, whose sales last year were 23.64 billion euros, or about $26.8 billion at current exchange rates. Floral Glass, a 49-year-old family owned business, was Long Island’s largest glass fabricator before it was bought by Oldcastle in 2004.

Other significant companies by size, age or technology, according to Levy, Buonavita and other industry experts, include Champion Metal & Glass Inc., a contract glazier in Hauppauge that has been ranked among the top 50 glaziers in the U.S. by USGlass, founded in 1993; Lynbrook Glass & Architectural Metals Corp., also in Hauppauge, a high-rise contract glazier and distributor founded in 1931; Quality Enclosures Inc., a Central Islip-based fabricator of tempered glass shower doors that started in 1963; and Glass America USA Inc., a West Babylon-based fabricator and distributor of architectural glass to the Northeast market founded in 1996.

Architectural glass comes in one of three basic types: monolithic, laminated or insulated.

Monolithic glass is a single panel, and is the building block of the other two. Depending on project specifications, it can be tinted, given a metallic coating that reduces UV penetration, or strengthened by a heat-treating process, or tempering.

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Laminated products are two or more pieces of glass sealed together with polyvinyl butyral in the middle, making it more resistant to impacts.

Insulated products have open air between two glass panels, which can be filled with various gases to either reduce sound or prevent loss of interior heat or cooling.

Working with glass is labor intensive, and occasionally dangerous.

A sheet of architectural glass, depending on the size or amount of layers, can weigh nearly 1,800 pounds. Fabricators typically receive sheets of raw glass from manufacturers.

The perception that working with glass is a danger makes it a challenge to find workers, said Scott Willett, the second-generation owner of Twin Pane The Glass Source, in Yaphank, a fabricator. “I think a lot of people are afraid of the idea of working with glass,” Willett said.

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Workers need to be alert. “Safety is a very big issue because a person could be hurt really seriously really quickly,” said Barry Litt, owner of Tower Insulating Glass in North Bellmore, a fabricator of architectural glass for high-end residential construction projects. “You’re dealing with very heavy weight and stuff that’s sharper than a razor. You can get cut and not even feel it.”

Inside his plant, hard hat-wearing employees move about the work stations as they lift large sheets of uncut glass. In the middle of the warehouse, glass is carefully set down before a laser-guided system operated by employees cuts it to size.

Litt said the products his fabrication firm makes have been used in high-priced Hamptons homes, and increasingly in Brooklyn and Queens as residential development drives demand for energy-efficient insulated glass.

Selling energy-saving products that are essentially invisible presents a marketing challenge for glass fabricators, Litt said. “They want it to save energy, they may want it to reduce UV penetration, and they may want it impact resistant,” said Litt. “Last but not least ... they want it as clear as possible.”

Some companies, such as Plainview-based Innovative Glass, seek to use new technology to drive demand.

Innovative, founded in 2003 by former consumer electronics entrepreneur Steve Abadi, sells liquid crystal, electronically activated privacy glass. The company contracts fabricators to “sandwich” paper-thin liquid crystal film between sheets of glass.

When electricity is applied, particles inside the film “line up,” making the glass clear. When deactivated, the film immediately reverts back to an opaque white frost. Abadi said his products, which also include adjustable tint glass, sell for as much as $250 a square foot to general contractors using them in buildings.

New technology allows a greater variety of products to be sold to builders, said Ali Ghahremani, president and founder of Champion Metal & Glass.

Ghahremani, who started Champion out of a spare bedroom in his home in 1993, said his company employs 110 and does more than 90 percent of its work in Manhattan. For the last five years, the company has been installing glass storefronts on more than 350 retail businesses under the new World Trade Center.

Inside Champion’s 40,000-square-foot shop, employees measure, cut and weld together aluminum framing systems that will eventually hold panels of glass in front of stores and outside offices. USGlass estimated Champion’s 2015 revenues at $28.7 million.

For Craftsman Storefronts & Glass Inc., based in Bay Shore, “Seventy percent of our work is between Nassau and Suffolk,” said John Sullivan, vice president.

Sullivan said the company, which had about $11 million in revenue in 2015 and is well ahead of that pace this year, gets a lot of work from high-end renovations and store openings, such as the Lord & Taylor in Manhasset and the 3-story addition for Memorial Sloan Kettering Commack.

One challenge for fabricators and glaziers is the rising cost of raw glass. In North America, there are only six major manufacturers left after a consolidation during the recession. While commercial construction has rebounded, raw glass making has struggled to keep up, leading to multiple price increases a a year, as high as 15 percent each.

Many in the industry believe that WHTB might become a direct competitor to Oldcastle. A spokesman for Oldcastle declined to comment.

WHTB plans to build a 50,500-square-foot fabrication and office facility on a 4.23-acre vacant lot along Ramsey Road near the Long Island Expressway in Shirley and hire more than 140 employees, according to a tax assistance application submitted in January to the Brookhaven Town Industrial Development and local attorney Bram Weber.

For others, a new company brings more options.

“To have more qualified players in the mix is always to our advantage,” Ghahremani said.