If you are in certain Dolce & Gabbana or Louis Vuitton stores, or the lobbies of several Bulgari or Four Seasons hotels, be sure to look up. You likely will see a large, dazzling, one-of-a-kind light fixture, every piece of glass mouth-blown on the Venetian island of Murano, just as it has been done for more than 700 years.

That is why you may see the same sort of chandeliers in paintings by Tintoretto and Titian, Caravaggio and Giorgione.

They all were made by Barovier&Toso, which markets itself as the oldest glassmaking operation on that island of glassmakers.

Its founder, Jacobello Barovier, moved from Venice to Murano in the late 1200s to work in glassmaking, just after the Republic of Venice, as it was at the time, required that all glassmaking be done on the island in an attempt to guard the industry’s trade secrets. He opened his own glassworks in 1295, and it operated independently until 1936, when it merged with the Toso glassmaking business.

Today, visitors to Murano can enter the Palazzo Barovier&Toso store on the Rio dei Vetrai, or the river of the glassmakers, as well as the business’s showroom, across the canal by footbridge. Inside the showroom is a heavy wood door marked with the company’s current name and the date 1295. Behind the door lies a large stone room used as storage, but in the 1500s, when the company came to this address, it was where the furnaces burned and glassblowers originally worked their magic.

Today, the work is done in adjoining rooms added over the years, each made of stone and with tall ceilings to absorb the heat as well as big windows to let in the light.

The process starts with the secret recipes that have been handed down in the family over the generations. Each partia, as the recipes are called, consists of varying amounts of sand, oxides, mineral salts and powder — every week, some 3,000 to 4,000 kilograms of these materials arrive on barges that have floated through the lagoon. (Partia is Venetian slang for partita, or quantity of goods, which in this case is sand.)

Furnaces blaze, as they always have, peaking at 1,400 degrees Celsius (2,252 degrees Fahrenheit) during the night to keep the partia molten and free of bubbles. Glassblowers, who train for as long as 20 years to master their art, still blow by mouth into long pipes to create balloons of viscous glass. The balloons then are manipulated until they turn into one of the thousands of pieces that go into creating a chandelier; the company also makes glass objet d’art, vases and drinking glasses.

The next steps require the finesse of craftsmen (very few women have worked in glassblowing over the centuries, as the work was considered too rigorous). They use an arsenal of vintage tools, including pliers, shears and templates, to create a piece.

Cooling ovens render the piece ready to be finished by hand, and various departments grind, polish, clean, assemble, pack and ship the finished product. Seventy-seven people work at Barovier&Toso, 30 in production. So far in 2022, turnover has reached $12.5 million.

Several techniques going back centuries are still employed by the company. Vetro a ghiaccio, or ice glass, is known to have been used as early as 1570, when it was mentioned on a map of Venice; the crazed surface is achieved by dipping the hot glass, still attached to the glassblower’s pipe, into water.

Rugiada, or dew, with its tiny fragments attached to the glass to give it the look of dew drops, was invented by Ercole Barovier in 1938. To obtain this glass, the surface is covered with many pieces of annealed melted glass, similar to small drops of dew; sometimes leaves of gold are added to embellish the object.

And to obtain a corteccia, or bark, finish, the blown glass is gently placed in a pear wood or cast iron mold, which gives the object’s surface the look of tree bark.

The company has managed to adapt its offerings to suit the style of the times, and today it turns to designers like the Dutch master Marcel Wanders or to Stefano Dolce and Domenico Gabbana to create fixtures for their brand’s Casa collection (individual pendant lights starts at $175,300)

As the Bulgari Group’s executive vice president in charge of hotels and resorts, Silvio Ursini, wrote in an email, Bulgari has had a long association with Barovier&Toso. The chandeliers, he wrote, make the hip hotels’ rooms turn into “jewels.”

Much of what Barovier&Toso produces is custom-made, and very expensive. On the lower end is the new Opera table lamp, inspired by the Opéra Garnier in Paris and designed by Philippe Nigro ($6,250).

The most elaborate piece that Barovier&Toso has created may be the 16-meter (almost 53 foot) chandelier that it made in the 1960s for the Montreal stock exchange in Canada. Another contender would be the chandelier it created in 1980 for a Saudi sheikh that required nearly 2,000 pieces, many with gold leaf. The piece has proved to be influential, with luxury brands like Dolce & Gabbana using a version in their boutiques around the world.

In 2015, the business’s owner, Jacopo Barovier, was ready to retire, and the only younger Barovier was unwilling to enter the business. After searching for a buyer with respect for artistry and heritage, Mr. Barovier decided to sell the business to Rinaldo Invernizzi, a local art collector and painter (who is having his first personal exhibition, titled “Smeraldo. Antracite. Cobalto,” as part of the 2022 Venice Biennale.)

“I am a great enthusiast and collector of artistic glass and therefore I knew the Barovier&Toso brand very well,” Mr. Invernizzi wrote in an email. “I took the opportunity and the challenge to lead this company with great fervor and respect.”

But he wrote that there would be some significant changes. “We are investing in technology and collaborations with designers, changing strategy at an organizational and managerial level, opening up to foreign markets and exporting these incredibly special works of glass all over the world,” he wrote.

“What most fascinates me is the feasibility and possibility of renewal, even for a reality such as that of ancient Murano glass art.”