Divine diversity: for many companies among the North Carolina 100, venturing into new markets has proved to be a blessing.

• Author: Lester, Margot
• Position: Profiles of Radiator Specialty Co., Coastal Wholesale Grocery Inc., and Thomas Built Buses Inc. - Cover Story

Buildings, buses, batteries, baked goods, beef. There's no lack of diversity among the North Carolina 100 - or within them, for that matter.

"If you track the history of the North Carolina 100 companies, you'll see numerous examples of diversification," notes T. Michael Henderson, a national director of the Center for Family Business at the accounting firm Arthur Andersen, which compiles the annual list of the state's largest private companies.

Here are three that have stayed on a growth path by not being reluctant to head off in new directions.

Radiator Specialty Co.

Radiator Specialty's diversification back in the late '20s and early '30s was almost accidental, the way Herman Blumenthal tells it. "My brother was sitting in a restaurant in Pennsylvania when some plumbers came in discussing how to fix the boiler at the town's small hotel," says the Charlotte-based company's chairman and CEO. "The boiler was leaking, and they couldn't shut it down for repair because it was the dead of winter." I.D. Blumenthal gave them some samples of the company's Solder Seal.

So what if it was made to plug leaky car radiators? It did the job. As the plumbers talked eagerly about other products they needed, Blumenthal took mental notes. That, together with things he picked up as he traveled across the country pushing his products, prompted him to buy Golden State Rubber Mills in Los Angeles in 1933.

So don't let the name fool you. Radiators are not the company's specialty. Over the years, it has moved away from specializing in automotive products by adopting a concerted diversification strategy. And that has put its products in a lot of places that matter to a lot of people. Under commodes, for instance. Its plumbing division makes wax rings (sold as Sealmaster) that seal toilets into place. Or out on the open road. There, construction crews use its line of bright-orange highway cones to divert traffic around road work.

In all, Radiator Specialty, which employs 550, has more than 4,000 automotive, hardware, plumbing and traffic-safety products. But it all started with a leaky radiator.

In 1924, I.D. Blumenthal was looking for a venture to take him out of the family's dime-store business in Savannah, Ga., and into his own. While in Charlotte on business, his Packard's radiator sprang a leak. Someone told him about a local tinsmith, George Ray, who'd developed a new way of repairing radiators.

Back then, fixing a leak meant removing and draining the radiator, soldering the leak shut, then refilling and reinstalling the radiator. Blumenthal took his car to Ray, who poured in what he called a "magic powder" that sealed the leak with aluminum. It had an expansion rate 30 times that of cast iron. The hotter the engine, the better it worked.

Blumenthal got permission to market the powder, now called Solder Seal for Ray. The first year was lean, but he stayed optimistic. The next year, orders were up, and he pressed Ray to give him a 50% interest. Radiator Specialty was incorporated in 1925 and operated for a while out of a 12-by-14-foot office. A decade later, when Ray died, Blumenthal bought out his interest from the estate.

The company's move into highway-safety products was inspired by another need Blumenthal thought he could fill. "My brother was...