Armed with an industrial-strength blowtorch and his trusty cell phone, Rabbi Ben-Tzion Welton wheels into action.

It’s going to be a crazy day.

Before it ends, the 52-year-old Berkeleyan will shoot flames at pots and pans, immerse a set of dishes in the warm waters of a blue-tiled mikvah behind his home, check out an apartment for some new colleagues moving to town and field multiple calls on a tiny Nextel.

Though his work as a mashgiach or kashrut supervisor demands a strict adherence to a complex set of Jewish dietary laws, Welton has anything but a rigid, by-the-clock schedule.

One day, he may head to a salad-packaging plant in the Monterey County town of Soledad to inspect lettuce for signs of bugs. On another, he may supervise the menu and food preparation for a 500-guest wedding in Foster City. Thrown into the mix are regular and often surprise visits to a Krispy Kreme Doughnuts outlet in Pinole, other eateries and some 50 Northern California food-processing plants that make kosher products.

“A mashgiach has to have a good car and a good cell phone,” quips Welton, a slight man with a long, wiry beard, glasses and a faded black cap.

Today, he’s borrowed a 15-passenger van from the local Chabad rabbi for the tasks ahead.

Mordechai “Moti” Dagan, a former partner at Oakland’s Grand Bakery, is opening a Middle Eastern cafe in Albany and wants to get his kosher certification in time for a big street fair on the weekend.

Welton wakes up at 5:30 a.m. and goes around back to the mikvah before heading off to morning minyan at Congregation Beth Israel, an Orthodox shul in Berkeley. Welton and Dagan meet up afterward and kibitz about the restaurant project.

The kashering is a big job, but doable. After all, Dagan “knows kosher” from his work at the kosher bakery, and much of his kitchen equipment is new, making the certification process relatively easy, the rabbi says.

Shortly after noon, Welton makes the 20-minute trip across town to the soon-to-open Sophia Café, where he loads up new dishes and pans that will undergo tevilah (also known as toiveling), immersion in the mikvah.

The process will elevate the equipment from “a mundane status to a holy status,” Welton explains.

Returning home, he waits for his 20-year-old son, Levi. Together, father and son push the stuff down a shaded driveway in an old baby stroller.

“This guy rode in it when he was a kid,” says Welton, a father of four, of his eldest son, now a yeshiva student.

Inside the spa-like cottage around back, Welton heads to the room containing the mikvah. Built in 1980, the ritual bath must be filled with “living water,” Welton says, describing how rain water is collected on the roof.

Welton says a blessing and then gently plunges some metal lids one by one into the water. He quickly catches each sinking object in a supermarket-style handbasket.

“The equipment has to be immersed in water totally,” Welton explains.

“We used to do it for Noah’s Bagels,” he adds, but the metal sheet pans used for baking were “a nightmare. There were hundreds and hundreds of them.” The mikvah water turned a murky gray and ultimately, the bath had to be drained and refilled.

On this day, there are no such worries and Welton turns the tevilah process over to Levi and his 15-year-old sister, Ashirah. The rabbi gathers up the tools he’ll need at the cafe — a serious-looking blowtorch and a propane tank.

They’re used in a second kashering process called libun, which burns off any nonkosher food from kitchen equipment and, in a more spiritual sense, any nonkosher taste. Another method, called hagalah, involves purging items in boiling water.

The methods — and Welton’s calling — date back to biblical times. Numbers 31:23 reads “any article that can withstand fire — these you shall pass through fire and they shall be clean, except that they must be cleansed with water of lustration” (ceremonially purified).

Of the three techniques, burning is clearly the most spectacular.

Packing up a long hose capped at the end with a metal nozzle, Welton says, “It’s really a roofer’s torch. We used to use little torches and it took forever.”

At Sophia, Welton’s work has been minimized. “Usually the hardest part is the stove, oven or fryer,” he says. “Clean is one thing. Kosher clean is another.”

Glancing at the new four-burner stove, he says, “This is spotless.”

Donning work gloves, Welton hooks the hose of the torch to the propane tank, opens the valve and with a big “whoosh” ignites the business end with a lighter.

He aims the blue flame at a 12-quart soup pot, cranks up the heat and slowly sweeps the jet of fire across the metal surface.

“We pay more attention to handles,” he says. “That’s where food gets trapped.”

When he’s done some two minutes later, Welton hoists the pot into the sink. Dagan turns on the faucet with a resulting cloud of steam.

“That’s hot,” the rabbi says with a satisfied grin.

The water helps to close the “pores of the metal” on the purified pot to any nonkosher taste. “It’s a living system,” he says.

Welton has spent 12 years as a kosher supervisor, with the last seven as the coordinator at Vaad Hakashrus, the kosher certification agency in Northern California. In the Bay Area, he is one of a handful of rabbis who work as mashgichim.

Reared in a Reform household in Michigan, Welton became increasingly spiritual in his 20s. “I just got more involved,” he says. “It resonated with me.”

Trained at a yeshiva in New York, Welton also holds an undergraduate degree in psychology and a master’s in public administration. Welton, whose speech is slurred as a side-effect of surgery he underwent as a teen, previously worked as a counselor for people with disabilities.

Kosher certification is a calling that came gradually. Referring to food as “a common denominator,” Welton said being a mashgiach is a way “I can make Judaism accessible.”

Spiritually, kashering creates an “awareness of all foods as a gift from above,” he says.

Eating kosher food “sensitizes you to what you’re doing, what you’re eating. You’re not just eating, you’re sanctifying your body with the food.”

Welton also likes the delicate “interface” between the outside world and the Jewish world.

“My father was a lawyer,” he said. “I always liked law.”

Still, a mashgiach’s work isn’t without risks.

About five years ago, Welton’s beard was scorched by flames that shot out of a leaky, and borrowed, propane tank he was using in an Oakland restaurant.

Last year, his knee gave out while supervising a catered party. He landed in bed for a month.

“Usually it’s when you’re tired,” he says of such mishaps.

As for kosher violations, they’re “very upsetting,” but unavoidable.

“I can count the gray hairs from certain things,” Welton says, rattling off past instances — like when a Noah’s worker unwittingly warmed his turkey sandwich in the microwave and when a dairy ice cream was inadvertently purchased for a catered meat meal.

“But you do your best,” he says. The art lies in “how you can recover from a mistake.”

The job sends Welton on the road three to four days a week, visiting factories and restaurants covering a wide swath of rural and urban Northern California.

The work, he says, is “99 percent calm and 1 percent sheer terror when you see something that’s wrong.”